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Brief CV and carreer

BEGINNING OF MY CAREER

I received my Engineering degree from the University of Tucumán, in Argentina in 1994. My first steps in research were in the Biomechanical Group of that University under the supervision of Drs. O. Bravo and E. Bertini, and it dealt with the design, evaluation, and application of vibration sensors based on piezoelectric accelerometers. I designed an automatic wheel equilibrating machine working with this accelerometer connected to the pc with a visual basic interface. The originality of the results related mainly to the sensitivity achieved for a low-cost accelerometer, much cheaper and comparable in quality to the scarce commercial ones. The results were presented in several meetings of the “Asociación de Física Argentina”, AFA 95 and AFA 96, and they constituted the subject of an engineering project for a student. During this research time in the group I also worked in various areas, related for example to the design of a wireless interface to any accelerometer, in order to register any event far away from the computer. We also designed a force platform, based on three lab-made axial piezo-accelerometers whereby we could study the foot-ground interaction, for early detection of diabetes, leading to an engineering thesis degree in the same topic.In those years the use of PIC micro-controllers were

not as generalized as nowadays, so my research was rather innovative.

After finishing my degree I started working in a private local company as an engeneer on a proyect focused on the management consulting and quality process (TQM) with Prof. Carlos Boquete.

In 1996 I became a senior executive in the Ericcson Company as a Regional Manager and two years later in Telefonca S.A as a Senior Executive.

 

  1. RESEARCH AT THE UNIVERSITY OF GRANADA: MAGNETORHEOLOGICAL FLUIDS

 

I later spent 5 years in the private sector, leading a few management positions in technological companies as Teléfonica and Ericsson. In those companies I worked as regional manager involved in wireless transmission, mobile device, network protocol and optic fiber to mention just a few. I moved in 2001 to Spain where I joined the Interfacial and Colloidal Systems group with a grant associated to a research contract with the financial support of Repsol Technology Center. The project was dedicated to the development of magnetorheological fluids (MR) with application in fluids for automobile dampers. This was also the topic of my Ph.D. Dissertation defended at the University of Granada in 2008.

The core of the project was the design and development of a new, stable MR fluid consisting of an oil phase with dispersed ferromagnetic particles (iron or magnetite) in the μm size range, responsible for the (MR) response. The performance of the fluid produced is qualitatively illustrated in Fig. 1.

Fig1-b.jpg

Fig.1.  Examples of tests performed in the MR fluid and particles used.

 

The fundamental problem of these fluids is their lack of stability, poor redispersibility, and aging behaviour. We succeeded in designing two stable and high-performance MR fluid formulations. One of them was the origin of one European (R1)and one Spanish patent. The former is licensed to Repsol as possible component of a future automobile MR damper. These fluids were tested with a real MR damper provided by Delphi Corporation and tested in the Polytechnic University of Madrid. Some results were published in the specialized journals Tribology Transactions [3(2008)271], J. Colloid Interface Sci. [377(2012)153] and recently in Smart Mater. Structure [23 (2014)085028](R2). The test damper machine and pictures of the damper are illustrated in Fig. 2.

Fig_2

Fig.2, Testing machine and picture of the MR shock absorber and basic behaviour.

As mentioned, one drawback of these fluids is their limited stability, which in fact is even difficult to evaluate in quantitative terms. I designed a new technique, which based on magnetic induction measurements yield the sedimentation profile as a function of time. The results were published in Review Sci. Instrum. [82(2011)073906] and J. Colloid Interface Sci. [311(2007)475]. The instrument (Fig. 3), still working in our laboratories, was awarded the “Emilio Herrera Linares” prize of the University of Granada in 2007. Dealing with the synthesis of magnetic nano-fluid I was awarded with an honour mention in Science in the competition “Ciencia en Acción2008”.

Fig2.jpg

Fig. 3.The device used in the determination of sedimentation profiles of MRF fluids, and an example of output, regarding a 10 % iron suspension.

The MR fluids design and application produced very wide and  interesting applications, some of which were patented as well, including an improved, adaptive crutch, Distributed-pressure saddle (licensed), and a kind of active shoes, also issued an Worldwide patent(WO2007125148 A1) to mention just a few. The designs are schematically shown in Fig. 4, and it attracted the interest of many footwear Spanish companies at that time.

Fig3.jpg Fig3.jpg
patente
 

 

 

 

 

 

 

 

 


Fig. 4.Left: schematics and principle of the MR-damped shoe. Right: adaptive crutch on the Right

 

  1. POSTDOCTORAL STAY: UNIVERSITY OF GRAZ, AUSTRIA

 

In April 2009 I obtained a postdoctoral position at the University of Graz as a senior researcher at the Physical Chemistry Department. In this research center, I worked with the prestigious researcher Dr. Otto Glatter on nanostructures and design of light scattering instruments to characterize different colloidal systems, solid-gel transitions, liquid crystals and arrested systems. In this period I learned the bases on Dynamic and Static Light Scattering, and Small Angle X-Ray Scattering (SAXS) techniques, self-assembly in colloidal systems and its characterization.

My initial investigations dealt with the cooperative behavior of anionic and nonionic surfactants producing a sort of hypercharging effect, in virtue of which adding the nonionic surfactant after the anionic one produces an increase in negative surface charge that was published in (R3)Soft Matter [7(2011)4619] and Langmuir [27(2011)9182], as depicted in Fig. 5.

Fig4.jpg

Fig. 5.Sketch illustrating the adsorption phenomena occurring at the silica/water interface.

 

My engineering background allowed me to participate in the design of several Light Scattering instruments and corresponding cell sample holders. I had the opportunity of working on and improving some details of the 3D DLS echo technique, one of the few instruments available in the world with this technique at that time. It is essential when working with highly concentrated or turbid systems, where the multiscattering effect often hinders measurements and data evaluation. The results were published in first-rank journals, including Physical Chemistry Chemistry Physical[13(2011)3004] and Langmuir[29(2013)15496]. Some relevant results are included in Fig. 6.

Fig5.jpg

Fig. 6.Left: SAXS data on transfer kinetics (phase change from H2 to cubic); center: arrested

dynamics in emulsion droplets entrapped in hydrogels; right: monoolein phases and their SAXS patterns.

 

In addition, during this period, I attended the interdisciplinary course “Dynamic Light Scattering and Methods”, organized by the University of Graz. I was one of the organizers of the meeting “From light scattering to application” held in Badgastain (Austria) on July 2011, in which researchers of different fields (Chemistry, Biology, Physics) presented the subject from their individual perspective. I also attended the 2th International Soft Matter Conference(5th-8th July,2010), andI presented the results obtained in the 24th Conference of the European Colloid and Interface Society (ECIS 2010) in Prague(5th-10th September 2010).

The collaboration with Prof. Glatter is still quite close at the moment thanks to a short stay in 2013. I have been working on the transition from ergodic to non-ergodic systems, and slow relaxation processes published in Langmuir[30(2014)3639]. These recent works are based on the instrument and the flat thin cell in whose design I collaborated. Its details are the topic of recent paper published in Colloids and Surfaces A: Physicochemical and Engineering Aspects (DOI: http://dx.doi.org/10.1016/j.colsurfa.2014.11.047); some are illustrated in Fig.7. This instrument could measure the short and long time correlation function with a novel implementation of the so-called “brute force” method introduced by Pusey and Van Megenin 1991, with a special design of the mechanical setup of the sample. In this case, the sample can be moved by a few microns up or down in order to obtain the fast decay below 1s, and a CCD chip records the long term behavior with the multispeckle method.

Fig6.jpg

 

Fig 7.Left to right and top to bottom: detail of the instrument setup; flat cell construction; example of correlation functions recorded; typical turbidity of samples which can be analyzed.

  1. RE-INCORPORATION TO GRANADA: CAPACITIVE MIXING FOR ENERGY PRODUCTION

 

During the last four years I joined again my former research group and found an excellent field of application for my engineering background. The opportunity came through a VII FP European Project, Capmix (www.capmix.eu). The basic idea of the consortium was exploring the possibility of gaining net energy from charged interfaces by simply allowing an exchange of the solutions in contact with the interface. The method is enclosed in a group of emergent technologies jointly known as Capmix methods, which are based on the change of the electrical properties of the electrode-solution interface associated to salinity variations. Their aim is to directly extract electric energy without conversions through turbines and thermal machines. The technique of interest for the research proposal is known as Capacitive energy extraction based on Double Layer Expansion (CDLE), is based on the fact that electrical double layers (EDLs) can accumulate a large amount of charge if the interfacial area is high enough, and that the capacitance of the EDL depends very significantly on the ionic contents of the medium. If a metal/solution interface is externally charged (using a battery, for instance) to some extent in the presence of high ionic strength, and discharged in low ionic strength (less capacitance, more potential for given charge), it might be possible to obtain a net amount of energy: the electrodes are charged at our expense in conditions of lower voltage, and discharged (delivering power) at higher voltage. The result is that electrical work is made available, without use of any kind of selective membranes or electromechanical devices.  The balance between diffusion and electrostatic interaction of both counter-ions and co-ions on each electrode will bring about the appearance of electric double layers and hence a profile of electric potential in the vicinity of the electrode (Fig. 8a). If sea water is exchanged for fresh water as the case may be in a river mouth, the potential profile would be different, as shown in Fig. 8b, where it is assumed that the exchange takes place in open circuit conditions. In that case, the surface charge density at the wall does not change and neither does the total charge at the EDL, which is redistributed in a thicker space. It can be seen that the electric potential increases (Fig. 8b).

Fig7.jpg Fig7.jpg

 

Fig. 8.a) Electric potential profile in the vicinity of a particle, for a surface potential  of 50 mV,

and 600 mM NaCl solution; b) expected potential jump after exchanging the 600 mM solution for a 20 mM one at constant charge. The EDL limits in each case are marked by vertical dashed lines.

 

Fig. 9 is a schematic representation of the energy extraction procedure.  The successive states of the system are as follows:

A: electrodes in salt water connected to the battery at an initial potential ψ0;

A→B: exchange for fresh water in open circuit (constant surface charge density);

B→C: battery reconnected in fresh water;

C→D: exchange for salt water in open circuit (constant surface charge density);

D→A: battery reconnected in salt water. The area of the cycle represents the net extracted work per unit area of electrode.

 

Fig8.jpg

 

Fig. 9.Left: schematic representation of the surface charge density vs. surface potential for two

NaCl concentrations. A possible CDLE cycle is marked by arrowed lines. The area of the

blue-shadowed region represents the energy extracted; right:model of the CDLE circuit.

I have been leading during the last three years the experimental aspects of the project. The starting point was the design of devices suited to the implementation of the cycles described, and the selection and treatment of the materials to be used (R4).I came to a design that proved excellent results when using both powdered carbon and carbon-coated films. This is illustrated in Fig. 10, where our best experimental cell is described in detail in the European patent PCT/ES2014/070722 publish in September 2014.

 

Fig9.jpg

Fig. 10.The experimental Capmix cell.

           

With this design, the group was capable of obtaining reproducible results and demonstrating that energy can be produced by means of the voltage jump associated to the salted-fresh water exchange (Fig. 11). The materials testing carried out in (R4) was also a very significant achievement of the candidate’s work.Moreover I am co-director of a PhD Student working in this project and the thesis will be defended by the end of 2015.

Fig10.jpg

Fig. 11.Left:Hydrophobic vs. hydrophilic carbon results; right: TEM picture of activated carbon particles.

 

Actual research and expected results

The project is very well suited to my background including physical properties of interfaces and of the engineering of devices aimed at obtaining information from experiments of the kind described. One of the future issues concerns the use of stacked cells approaching the real world, and energy gains in reasonable ranges. I have designed several (multiple electrode) cells, some of which are shown in Fig. 12. We have already tested one of them, and the work in the coming months will help in deciding if the other designs are equally viable. This work   will be publishing in the next months.

Fig12.jpg

Fig. 12. Different stacked cells designed for increasing energy production (triple, series, hollow shell).

 

This project has finalized in September 30 of 2014, but the research open other improvements related with other variables in the process. The study of the temperature effects on energy production is one example, and preliminary results have already been published in a high impact factor journal, Environmental science & technology[48(2014)12378](R5). Some details of the processes are shown in Fig. 13

 

 

Abstract Image

Left: Model of the CDLE circuit with temperature exchange.

Right: potential increase in the capmix cycle

 

Another issue to study was the multi-ionic effect related with the real composition of river/sea water. This study gives us an overview of the possible effects of the deviation from the solutions prepared in the lab to the real water, with ion composition actually found in rivers and seas. Fig 14 shows some detail of the research, published in the Journal of Colloid and Interface Science [DOI: 10.1016/j.jcis.2014.08.009].

Full-size image (10 K)figura

 

Fig. 14. Left:CDLE circuit and Center: Extracted energy water type comparison.

Right: SEM Picture of natural seawater and detail of deposited organic shells and impurities

 

Continuing with the aim of gaining energy, but working now on a different type of electrodes, we worked with polyelectrolyte-coated carbons. With this research we found out that the “coating” is one of the key points to improve the efficiency in this method and we obtained a power of 12.1 mW m−2(Phys. Chem. Chem. Phys.16(2014)25241]. The increased efficiency and energy production as well the reduction of leakage in the system are our priority, and we are working at the moment focusing on the evaluation of different active carbons with various pore sizes, with promising new results.

 

SMART MATERIAL AND SMART DAMPERS

 

Simultaneously, I have maintained a close collaboration with Prof. Juan de Dios García López-Durán in the Project “Diseño de amortiguadores inteligentes para electrodomésticos basados en lubricantes magentoviscosos”  (IPT-020000-2010-006) in collaboration with Fagor Electrodomésticos and Mondragón GoiEskola Politeknikoa in order to design a low cost friction damper to be installed in a new high-quality washing machine.  The final results were used in two patents. One is the MR fluid and the damper container (European Patent (PCT/ES2013/070443), and the other deals with the friction damper working with MR elastomers [Patent number: 2.422.804]. Fig 15 shows some details of the design.In relation with the same topic, I have been involved in teaching a Master course on the use of smart dampers for vibration control in structures.

Fig11-b.jpg

Fig. 15.Details of the MR damper and vibration recorded in the washing machine with and without magnetic field applied to the damper

In the same topic I have supervised a master student from the UNAM (“Universidad NacionalAutónoma de México”) working on a project entitled “Arquitectura sin prótesis, prototipo para un material sismo-resistente” which deal with the design of new seismic dampers for protection of small buildings against earthquakes using aluminous porous sponge. In this work it is proposed the creation of a seismic impact absorbing device, using the MR effect in the form of a panel for steel structures from 1 to 6 story frames, to improve its protecting effect during an earthquake. In Fig 16 show some detail of the location of the proposed device. This cooperation with the University finished at the end of 2013 with a just accepted publication in Intelligent Material Systems and Structures.

 

Fig. 16 Theoretical location of the energy dissipating device in the architecture structural system.

(b) Details of the operation: configurations in field-off and field-on conditions

 

The collaboration with other groups of my university is one of my continued objectives, as a key to develop new interdisciplinary research. With this aim, I am already collaborating with one Civil Engineering group, where we have just patented a novel smart material for asphalt constructions called "Mechanomutable asphalt binders for the construction of smart pavements" PCT/ES2014/071002.In the coming months we are planning to finish a few publications in this area dealing with the special behavior of the binder proposed when it is affected by a magnetic field like self-healing, less contaminant and more efficient. The capacity of the healing is shown in Fig 17.

 

 

 

Fig. 17.Scheck of the healing capacity of the “mechanomutable” binders

 

In collaboration with Repsol Technology Center  we are currently working in a research dealing with Wear Preventive Characteristics of Magnetorheological Lubricating Fluid for automobile application.  The content of metallic particles is an important issue to study due the high friction inside the damper. For this evaluation, we have tested different MR lubricant in Four-Ball Method - ASTM D 4172. We measured the degree of wear scar and the rheological properties before and after the test. This research will be publishing in the next months. In Fig. 18 It is shown the trace of the ball wear for three MR lubricant.

 

 

wear_repsol.jpg

Fig.18. Left: Four-Ball machine: Center: Trace of wear; Right : TEM picture of different Iron particle composition

Due my background in electronic design, I am currently working with the department of Electronicsand Computer Technology as a co-director of two degree theses: one is aimed at a new design of the scanning settling instrument, based on the 3D printer design and a high accuracy electronic circuit. The details of the new instrument and its electronics are shown in Fig 19.

 

 

electronica-page-001

 

Fig.19.Left: 3D layout of the mechanical design of the magnetic fluid settling device; Right: electronic circuit

The other thesis is part of a new project in the group dealing with the design of a hyperthermia device for cancer treatment. It is based on the fact that magnetic nanoparticles, when subjected to an alternating magnetic field, produce heat. As a consequence, if magnetic nanoparticles are put inside a tumor and the whole patient is placed in an alternating magnetic field of well-chosen amplitude and frequency, the tumor temperature would rise and the cancer cells would be killed.The particles in a fluid move and rotate randomly (Brownian motion); when a magnetic field is applied to them magnetic nanoparticles rotate and progressively align with the magnetic field due to the torque generated by the interaction of the magnetic field with the magnetization (similar to a compass). The delay between the magnetic field reversal and the one of the magnetization leads to a hysteresis. The area of the hysteresis loop is a measure of the energy dissipated in the environment as thermal energy, and this is the energy used in magnetic hyperthermia. Normally temperatures should reach about 39ºC to 44ºC which can directly cause damage the cancer cells. This project has two parts, one of them is thesynthesis of a different kind of nanoparticles susceptible for the hyperthermia treatment. The synthesis of these particles is an important issue on their hyperthermia properties. The second is the design of an instrument capable of producing the movement of the particles (or of their magnetic moments):the frequency and power of the ac magnetic field is an essential issue, as it is necessary to have a high field with frequencies in the range of hundreds of kHz.  The idea is based on a RF power oscillator and a work coil where the sample is inserted. In Fig 20 it is shown the experimental setup and work coil and sample under test. In collaboration with the University of Jaen, I am co-director of a thesis degree related to the study and simulation of the parameters involved in the hyperthermia treatments.

IMG_0885.JPGIMG_0888.JPG

Fig.20. Experiment setup and work coil design under test..



 My current research lines are the following. A short list of research projects in these areas is located in the Projects section of the web.

  • Capacitive mixing as a novel principle for generation of clean renewable energy from salinity differences.
  • Light Scattering methods and instrumetation design
  • Experimental characterization of the rheological and stability properties MR fluids.
  • Design Magnethoreological (MR) Damper.
  • Arrested System and how could be measured.

 Research publications in international conferences, journals and patents are shown in the following list. When possible, the PDF file of each publication will be included.

Publication

  1. mechanomutable asphalt mortars for their use in smart materials
  2. Volume 25, Number 11

Smart Materials and Structures 2016-11-01 ISSN: 0964-1726
Impact: 2.769; 5/(56); 65(271)
DOI: 10.1088/0964-1726/25/11/115036
F Moreno-Navarro, G R Iglesias and M C Rubio-Gámez
Abstract
Mechanomutable asphalt binders are a new generation of smart materials, which are able to change their mechanical response to the load conditions suffered during their service life. These binders are composed of a bituminous matrix and iron micro-particles that can be activated with an external magnetic field, which induces mechanical changes in the system. However, these particles are expensive and they considerably increase the cost of these materials, reducing their competiveness. Thus, the aim of this work is to study the viability to produce more sustainable and low-cost mechanomutable asphalt mortars using stainless steel slag (SSS). This by-product is obtained from the production of stainless steel and contains a significant quantity of iron that could be used to activate the response of these materials. Different sizes and concentrations of SSS were used to manufacture mechanomutable asphalt mortars, and their mechanical behavior was then examined using several rheological tests. The results show that it is possible to achieve changes in the rheological response of these smart asphalt materials, thereby obtaining mechanomutable mortars from the stainless steel by-products. The efficiency of the slag also appears to be more dependent on its iron content than on its concentration or particle size

  1. Simultaneous hyperthermia and doxorubicin delivery from polymer-coated magnetite nanoparticles

Journal of Magnetism and Magnetic Materials 2016 ISSN: 1045-389X
Impact: 2.357; 78/(271); 23(67)
DOI: 10.1016/j.jmmm.2016.08.023.
G.R. Iglesias, A.V. Delgado, F. González-Caballero, M.M. Ramos-Tejada
Abstract
In this work, the hyperthermia response, (i.e., heating induced by an externally applied alternating magnetic field) and the simultaneous release of an anti-cancer drug (doxorubicin) by polymer-coated magnetite nanoparticles have been investigated. After describing the setup for hyperthermia measurements in suspensions of magnetic nanoparticles, the hyperthermia (represented by the rate of suspension heating and, ultimately, by the specific absorption rate or SAR) of magnetite nanoparticles (both bare and polymer-coated as drug nanocarriers) is discussed. The effect of the applied ac magnetic field on doxorubicin release is also studied, and it is concluded that the field does not interfere with the release process, demonstrating the double functionality of the investigated particles.

  1. Stacking of capacitive cells for electrical energy production by salinity exchange V. 318 Pág.283-290

Journal of Power Sources 2016-06 (ISSN: 0378-7753)
Impact: 6.333; 22/(144); 2(27);8/(88);26/(271)
DOI: 10.1016/j.jpowsour.2016.04.026
Iglesias, GR; Ahualli, S; Fernandez, MM; Jimenez, ML; Delgado, AV.
Abstract
In this paper we explore methods for stacking individual cells in order to increase the amount of energy that can be extracted from salinity gradient cycles (capmix methods). Each of the cells consists of a pair of parallel electrodes made of activated carbon particles, either bare or coated by a layer of polyelectrolyte. In these methods, energy is produced based on the modifications of the electrical double layer (EDL) structure in the pores of the carbon particles upon exchange of the salinity of the surrounding medium. In the case of the bare carbon particles, the electrodes are externally charged in presence of high-salt concentration, and discharged after exchanging the solution for a dilute one (sea-vs. river-water cycles). In a first stacking approach, we simply connect the electrodes side-by-side and only the outermost ones can be connected to the external source. Using a stack where potential and current between cells can be measured, it is shown that only the external electrodes seem to work, and it is suggested that this is a consequence of internal short-circuit currents between oppositely charged electrodes of different cells through the electrolyte. In contrast, the side-by-side configuration is operational if coated electrodes are used.

  1. Synergy between magnetorheological fluids and aluminum foams: Prospective alternative for seismic damping Vol.: 27. N:7 Pag.: 872-879.

Journal of Intelligent Material Systems and Structures
2016 ISSN: 1045-389X
Impact: 1.975; 105/(271)
DOI: 10.1177/1045389X15596624
Portillo, MA; Lozada, PSA; Figueroa, IA; Suarez, MA; Delgado, AV; Iglesias, GR.
Abstract
This article presents the experimental study of a preliminary investigation of a seismic damper device aimed at improving the behavior of structures when subjected to earthquakes. The damper is the result of a binomial material formed by an aluminum foam with pores of 1mm diameter wetted by a magnetorheological fluid. The objective of this work is to explore the synergy between the two components on a magnetorheological test and to evaluate the effect of the Al foam pores in the structure buildup of the fluid. The analysis is completed with a compressive test carried out on the magnetorheological fluid-filled foam in the presence of a magnetic field. This kind of test demonstrates that the deformation of the foam for very small loads is limited by the hardening of the fluid because of its magnetorheological response. The results of this research suggest that there is a mutual benefit between the components of the device, presumably leading to an enhanced dissipation of vibration energy

  1. Electric birefringence spectroscopy of montmorillonite particles Volumen: 12 Número: 22 Páginas: 4923-4931

Soft Matter 2016 ISSN: 1744-683X
Impact: 3.798; 40/(144); 49(271);7/(79);10/(85)
DOI: 10.1039/c6sm00512h
Arenas-Guerrero, P; Iglesias, GR; Delgado, AV; Jimenez, ML.
Abstract
Electric birefringence (EB) of suspensions of anisotropic particles can be considered an electrokinetic phenomenon in a wide sense, as both liquid motions and polarization of the electrical double layer (EDL) of the particles participate in the process of particle orientation under the applied field. The EB spectrum can be exploited for obtaining information on the dimensions, average value and anisotropy of the surface conductivity of the particles, and the concentration and Maxwell-Wagner polarization of the EDLs. It is thus a highly informative technique, applicable to non-spherical particles. In this paper, we investigate the birefringent response of plate-like montmorillonite particles as a function of the frequency and amplitude of the applied AC electric field, for different compositions (pH, ionic strength, particle concentration) of the suspensions. The transient electric birefringence (i.e., the decay of the refractive index anisotropy with time when the field is switched off) is used for estimating the average dimensions of the particle axes, by modeling it as an oblate spheroid. The obtained values are very similar to those deduced from electron microscopy determinations. The frequency spectra show a very distinct behaviour at low (on the order of a few Hz) and high (up to several MHz) frequencies: the a and Maxwell-Wagner-O'Konski relaxations, characteristic of EDLs, are detected at frequencies above 10 kHz, and they can be well explained using electrokinetic models for the polarization of EDLs. At low frequencies, in contrast, the birefringence changes to negative, an anomalous response meaning that the particles tend to orient with their symmetry axis parallel to the field. This anomaly is weaker at basic pH values, high ionic strengths and low concentrations. The results can be explained by considering the polydispersity of real samples: the fastest particles redistribute around the slowest ones, inducing a hydrodynamic torque opposite to that of the field, in close similarity with the results previously described for the mixtures of anisometric particles with small amounts of spherical nanoparticles.

  1. Magnetic hyperthermia with magnetite nanoparticles: electrostatic and polymeric stabilization Volume 294, Issue 10, pp 1541–1550

Colloid and Polymer Science 2016
Impact: 1.890; 86/(144); 85(34)
DOI: 10.1007/s00396-016-3918-3
G. Iglesias, A.V. Delgado, M. Kujda, M.M. Ramos-Tejada
Abstract
In this work, magnetic hyperthermia, i.e., heating induced by an alternating magnetic field acting on a magnetic suspension, is considered in three main aspects. The first one regards the implementation of a simple device for producing AC magnetic fields. The second contribution concerns the comparison of the hyperthermia response (measured by the specific absorption rate (SAR)) of magnetite nanoparticles of two different sizes and of raw particles vs. polyelectrolyte-coated ones. An improvement is observed of the SAR values when the pH is fixed away from the isoelectric point or when the ionic strength is kept at low values. The addition of a polymer enhances significantly the stability of the suspensions and so does with the SAR values. Finally, we describe the implementation of a sort of magnetic hyperthermia applicator, avoiding the necessity of placing the magnetic sample inside the coil and making it of more practical use.

 

  1. Mechanical performance of mechanomutable asphalt binders under cyclic creep and recovery loads Vol.: 113 Pág. 506-512

Construction and Building Materials 2016.  ISSN: 0950-0618
Impact: 2.421; 9/(61); 15/(126);75/271)
DOI: 10.1016/j.conbuildmat.2016.03.042
Moreno-Navarro, F; Iglesias, GR; Rubio-Gamez, MC.
Abstract
Mechanomutable asphalt binders are able to modify their mechanical behavior when they are activated by a magnetic field. Under the effect of the magnetic field, these binders can increase their stiffness and perform elastically, and once the magnetic field is removed, the material recovers its original visco-elastic properties. Because of this fact, these smart materials could offer a wide range of interesting engineering applications. One such use could be its incorporation into structures that are required to support cyclic loading, such as asphalt pavements, as they can be punctually activated to minimize the impact of traffic loads. Based on these considerations, this paper studies the mechanical performance of mechanomutable asphalt binders under cyclic loads similar to those occurring in real pavements during their service life. For this purpose, a magneto-rheometer has been used to carry out different multiple stress creep and recovery tests under different magnetic field strength. The results obtained show that, in spite of the fact that these binders do not have a significant recovery capacity, they can reduce the cumulative permanent deformations produced in them due to the effect of cyclic loads when they are under the effect of a magnetic field

  1. Development of mechanomutable asphalt binders for the construction of smart pavements Vol.: 84, Pág.: 100-109

Materials & Design 2015. . ISSN: 0264-1275
Impact: 3.997; 45/(271)
DOI: 10.1016/j.matdes.2015.06.098
Moreno-Navarro, F; Iglesias, GR; Rubio-Gamez, MC.
Abstract
A new generation of asphalt binders with mecanomutable properties has been developed, with the aim of obtaining smart materials able to adapt their mechanical performance to the real changing load conditions that occur during their service life. These materials are composed of a bituminous matrix that has been modified with magnetic particles that are able to change the mechanical behavior of the binder when they are activated by a magnetic field. This study examines the main variables that govern the mechanical behavior of these materials. The mechanomutable performance of different binders has been demonstrated under various concentrations of magnetic particles. In particular, these binders could increase their stiffness and perform elastically when they are activated by a magnetic field (even at high temperatures), which, once removed, enables the initial properties of the binders to be recovered. The changes induced in the properties of the binder depend on the amount of magnetic particles, the intensity of the magnetic field, and the type of bituminous matrix. The findings open up the possibility of a wide field of applications for its implementation in smart infrastructures, with special interest in the construction, rehabilitation, and maintenance of asphalt pavements

  1. Dynamic and wear study of an extremely bidisperse magnetorheological fluid V. 24 Num: 12, 127001

Smart Materials and Structures 2015 ISSN: 0964-1726
Impact: 2.769; 5/(56); 65(271)
DOI: 10.1088/0964-1726/24/12/127001
Iglesias, GR; Ruiz-Morón, LF; Duran, JDG; Delgado, AV
Abstract
In this work the friction and wear properties of five magnetorheological fluids (MRFs) with varying compositions are investigated. Considering that many of the proposed applications for these fluids involve lubricated contact between mobile metal-metal or polymer-metal parts, the relationship between MR response and wear behavior appears to be of fundamental importance. One of the fluids (MR#1) contains only the iron microparticles and base oil; the second and third ones (MR#2 and MR#3) contain an anti-wear additive as well. The fourth one (MR#4) is a well known commercial MRF. Finally, MR#5 is stabilized by dispersing the iron particles in a magnetite ferrofluid. The MR response of the latter fluid is better (higher yield stress and post-yield viscosity) than that of the others. More importantly, it remains (and even improves) after the wear test: the pressure applied in the four-ball apparatus produces a compaction of the magnetite layer around the iron microparticles. Additionally, the friction coefficient is larger, which seems paradoxical in principle, but can be explained by considering the stability of MR#5 in comparison to the other four MRs, which appear to undergo partial phase separation during the test. In fact, electron and optical microscope observations confirm a milder wear effect of MR#5, with almost complete absence of scars from the steel test spheres and homogeneous and shallow grooves on them. Comparatively, MR#2, MR#3 and, particularly, MR#1 produce a much more significant wear.

  1. Dynamics of liquid-crystalline emulsion droplets arrested in hydrogels: Addressing the multiple scattering problem in turbid systems Volumen: 480  Páginas: 197-202

Colloids and Surfaces A: Physicochemical and Engineering Aspects
2015. ISSN: 0927-7757
Impact: 2.761; 56/(144)
DOI: 10.1016/j.colsurfa.2014.11.047
Iglesias, GR; Pirolt, F; Tomsic, M; Glatter, O.
Abstract
Performing dynamic light scattering (DLS) measurements on turbid samples is still a great challenge. A standard DLS instrument will provide reliable measurements as long as the sample is transparent and ergodic. Measurements on highly concentrated systems, on the other hand, such as glasses or gels, show partially frozen dynamics or incomplete relaxation processes. Such systems are called nonergodic. Nonergodic systems commonly appear in various practical applications and are therefore of great scientific as well as industrial interest. Many of these systems show high turbidity caused by the multiple scattering. The contribution of multiple scattering accompanied by low light transmission often leads to false DLS results for such systems, since standard DLS theory is only valid for single-scattered light. We describe here a DLS instrument that has been modified to address this problem. We use a charge-coupled device (CCD) camera as a multispeckle detector, and combine single-mode fiber optics with a photomultiplier to determine both ensemble and time-averaged autocorrelation functions. The instrument features a thin, flat sample cell with a translation stage. We show some DLS results for a series of turbid colloidal suspensions, where the lipid droplets are entrapped in polymeric hydrogels of different polymer concentrations. We focus on the transition from ergodicity to nonergodicity using ensemble-averaged DLS-intensity autocorrelation functions.

  1. Stability behavior of composite magnetorheological fluids by an induction method Volumen: 26  Número: 14  Páginas: 1836-1843

Journal of Intelligent Material Systems and Structures 2015
ISSN: 1045-389X
Impact: 1.975;105/(271)
DOI: 10.1177/1045389X15577656
Iglesias, GR; Roldan, A; Reyes, L; Rodriguez-Arco, L; Duran, JDG
Abstract
In this work, we study the stability behavior of composite magnetorheological fluids consisting of magnetic (iron) and non-magnetic (poly(methylmethacrylate)) particles dispersed in mineral oil. Because of the opacity of the suspensions, optical methods traditionally employed for evaluation of the gravitational settling in colloidal suspensions are not suitable for sedimentation follow-up in this case. For this reason, we use an alternative method based on the evaluation of the resonant frequency of the inductance of a thin coil surrounding the sample. The movement of the coil along the height of the container at specified steps and time intervals allows obtaining information about the local volume fraction of particles inside the tube. The obtained successive profiles for the multi-component suspensions show a decrease of the iron particle settling and of the initial rate of settling as the poly(methylmethacrylate) volume fraction is increased. Finally, the increase of the poly(methylmethacrylate) concentration gives rise to an improvement of the rheological properties upon magnetic field application for a given concentration of iron. Both a strong rheological response and a good colloidal stability are essential for practical applications.

  1. Materials selection for optimum energy production by double layer expansion methods Volumen: 261 Páginas: 371-377

Journal of Power Sources 2014-09 ISSN: 0378-7753
Impact: 6.217; 2/(28); 6/(89)
DOI: 10.1016/j.jpowsour.2013.12.125
Iglesias, GR; Fernandez, MM; Ahualli, S; Jimenez, ML; Kozynchenko, OP; Delgado, AV.
Abstract

The capacitive mixing procedure for energy extraction based on Double Layer Expansion (CDLE) belongs to the group of so-called CAPMIX techniques, which aim at obtaining energy from the salinity difference between fresh and sea waters. Specifically, the CDLE technique takes advantage of the voltage rise that occurs when sea water is exchanged for river water in a pair of porous electrodes which jointly behave as an electrical double layer supercapacitor. In this article, we deal with some experimental aspects that appear essential for optimizing the extracted energy, and have not yet been analyzed with sufficient detail. This investigation will help in evaluating those parameters which need to be fixed in a future CDLE device. These include the charging potential, the durations of the different cycle steps, the load resistance used, and the porosity and hydrophilicity of the carbon.

 

  1. Multi-ionic effects on energy production based on double layer expansion by salinity exchange Volumen: 446 Páginas: 335-344

Journal of Colloid and Interface Science 2014-08 ISSN: 0021-9797
Impact: 3.368; 42/(139)
DOI: 10.1016/j.jcis.2014.08.009
Fernandez, MM; Ahualli, S; Iglesias, GR; Gonzalez-Caballero, F; Delgado, AV; Jimenez, ML.
Abstract
It has been recently shown that the free energy change upon salinity mixing in river mouths can be harvested taking advantage of the fact that the capacitance of charged solid/liquid interfaces (electrical double layers, EDLs) depends strongly on the ionic composition of the liquid medium. This has led to a new generation of techniques called Capmix technologies, one of them (CDLE or capacitive energy extraction based on DL expansion) based precisely on such dependence. Despite the solution composition playing a crucial role on the whole process, most of the research carried out so far has mainly focused on pure sodium chloride solutions. However, the effect of other species usually present in river and seawaters should be considered both theoretically and experimentally in order to succeed in optimizing a future device. In this paper, we analyse solutions of a more realistic composition from two points of view. Firstly, we find both experimentally and theoretically that the presence of ions other than sodium and chloride, even at low concentrations, may lead to a lower energy extraction in the process. Secondly, we experimentally consider the possible effects of other materials usually dispersed in natural water (mineral particles, microbes, shells, pollutants) by checking their accumulation in the carbon films used, after being exposed for a long period to natural sea water during CDLE cycles.

  1. Lipid Transfer between Submicrometer Sized Pickering ISAsome Emulsions and the Influence of Added Hydrogel V30, N10 Pag 2639-2647

Langmuir 2014 ISSN: 0743-7463
Impact: 4.457; 30/(157); 33(139);35/(260)
DOI: 10.1021/la404583y
Sadeghpour, A; Pirolt, F; Iglesias, GR; Glatter, O.
Abstract
Transfer of lipids between droplets in Pickering emulsions has been studied by time-resolved small-angle X-ray scattering (SAXS). The special features of self-assembled liquid-crystalline phases have been applied to examine the kinetics of internal phase reorganization imposed by lipid release and uptake by the droplets. The findings reveal faster transfer kinetics in Pickering emulsions than in emulsions stabilized with Pluronic F127. It is shown that the transfer kinetics can be accelerated by adding free surfactant to the dispersions and that this acceleration becomes more dominant when micelles are formed. The effect of immobilization of the droplets has been studied by incorporating them into the appropriate hydrogel network. The droplets are arrested, and the transfer slows down significantly at high enough concentrations of the hydrogel where nonergodic systems are obtained.

  1. Effect of Solution Composition on the Energy Production by Capacitive Mixing in Membrane-Electrode Assembly V.118 N.29 Pag. 15590-15599

Journal of Physical Chemistry C 2014 ISSN: 1932-7447
Impact: 4.772; 29/(129); 32(260);21/(80)
DOI: 10.1021/jp504461m
Ahualli, S; Fernandez, MM; Iglesias, G; Jimenez, ML; Liu, F; Wagterveld, M; Delgado, AV
Abstract
In this work, we consider the extent to which the presence of multivalent ions in solution modifies the equilibrium and dynamics of the energy production in a capacitive cell built with ion-exchange membranes in contact with high surface area electrodes. The cell potential in open circuit (OCV) is controlled by the difference between both membrane potentials, simulated as constant volume charge regions. A theoretical model is elaborated for steady state OCV, first in the case of monovalent solutions, as a reference. This is compared to the results in multi-ionic systems, containing divalent cations in concentrations similar to those in real seawater. It is found that the OCV is reduced by about 25% (as compared to the results in pure NaCl solutions) due to the presence of the divalent ions, even in low concentrations. Interestingly, this can be related to the "uphill" transport of such ions against their concentration gradients. On the contrary, their effect on the dynamics of the cell potential is negligible in the case of highly charged membranes. The comparison between model predictions and experimental results shows a very satisfactory agreement, and gives clues for the practical application of these recently introduced energy production methods.

  1. Polyelectrolyte-coated carbons used in the generation of blue energy from salinity differences V.16 N.46 P.: 25241-25246

Physical Chemistry Chemical Physics 2014 ISSN: 1463-9076
Impact: 4.493; 32/(139); 6(34)
DOI: 10.1039/c4cp03527e
Ahualli, S; Jimenez, ML; Fernandez, MM; Iglesias, G; Brogioli, D; Delgado, AV
Abstract
In this work we present a method for the production of clean, renewable electrical energy from the exchange of solutions with different salinities. Activated carbon films are coated with negatively or positively charged polyelectrolytes using well-established adsorption methods. When two oppositely charged coated films are placed in contact with an ionic solution, the potential difference between them will be equal to the difference between their Donnan potentials, and hence, energy can be extracted by building an electrochemical cell with such electrodes. A model is elaborated on the operation of the cell, based on the electrokinetic theory of soft particles. All the features of the model are experimentally reproduced, although a small quantitative difference concerning the maximum open-circuit voltage is found, suggesting that the coating is the key point to improve the efficiency. In the experimental conditions used, we obtain a power of 12.1 mW m(-2). Overall, the method proves to be a fruitful and simple approach to salinity-gradient energy production.

  1. Temperature effects on energy production by salinity exchange Volumen: 48 Número: 20 Páginas: 12378-12385

Environmental Science and Technology 2014 ISSN: 0013-936X
Impact: 5.330; 3/(47); 10(223)
DOI: 10.1021/es500634f
Ahualli, S; Fernandez, MM; Iglesias, G; Delgado, AV; Jimenez, ML
Abstract
In recent years, the capacitance of the interface between charged electrodes and ionic solutions (the electric double layer) has been investigated as a source of clean energy. Charge is placed on the electrodes either by means of ion-exchange membranes or of an external power source. In the latter method, net energy is produced by simple solution exchange in open circuit, due to the associated decrease in the capacitance of the electric double layer. In this work, we consider the change in capacitance associated with temperature variations: the former decreases when temperature is raised, and, hence, a cycle is possible in which some charge is put on the electrode at a certain potential and returned at a higher one. We demonstrate experimentally that it is thus viable to obtain energy from electric double layers if these are successively contacted with water at different temperatures. In addition, we show theoretically and experimentally that temperature and salinity variations can be conveniently combined to maximize the electrode potential increase. The resulting available energy is also estimated.

  1. Theoretical and experimental evaluation of the flow behavior of a magnetorheological damper using an extremely bimodal magnetic fluid Volumen: 23 Número: 8 Número de artículo: 085028

Smart Materials and Structures 2014 ISSN: 0964-1726
Impact: 2.502; 8/(56); 59(260)
DOI: 10.1088/0964-1726/23/8/085028
Iglesias, GR; Ahualli, S; Otero, JE; Ruiz-Moron, LF ; Duran, JDG
Abstract

The flow behavior of a magnetorheological (MR) fluid, consisting of iron particles dispersed in a ferrofluid carrier ('MRFF') in a commercial monotube MR shock absorber is studied. The magnetorheological properties of the MRFF suspensions are compared with those of a conventional oil-based MR fluid ('MRF'). The mechanical behavior of the MR damper, filled with the MRFF or alternatively with the MRF, is characterized by means of different oscillatory force-displacement and force-velocity tests. The MR shock absorber has an internal electromagnet that generates a controlled magnetic field in the channels through which the MR suspensions flow under operation conditions. The results obtained indicate that the damper filled with MRFF shows a reliable and reproducible behavior. In particular, the response of the shock absorber can be controlled to a large extent by adjusting the electromagnetic current, showing a response that is independent of the mechanical and magnetic history of the MRFF. The non-linear hysteresis model proposed for predicting the damping force provides good agreement with the experimental results when the MRFF is employed. The improved response of the damper loaded with ferrofluid-based MRFF (instead of the conventional MRF) is explained considering the physical properties and the internal structure of the suspension

  1. Lipid Transfer in Oil-in-Water Isasome Emulsions: Influence of Arrested Dynamics of the Emulsion Droplets Entrapped in a Hydrogel Langmuir 2013 ISSN: 0743-7463

Impact: 4.384; 28/(148); 31(136); 31/(251)
DOI: 10.1021/la4032255
Iglesias, GR; Pirolt, F; Sadeghpour, A; Tomsic,; Glatter, O
Abstract
The transfer kinetics of lipids between internally self-assembled droplets of O/W emulsions is studied. The droplets (isasomes) consist of various liquid-crystalline phases or W/O microemulsions stabilized by a polymeric stabilizer F127. The various internal phases were identified by the relative peak positions in the small-angle X-ray scattering (SAXS) curves. An arrested system composed of isasomes embedded in a gel matrix actually provides an additional possibility to control these systems in terms of the release of various host molecules. These experiments have been applied to examine the kinetics of the internal phase reorganization imposed by the lipids' release and uptake by the droplets embedded in a kappa-carrageenan (KC) hydrogel network. Increasing the concentration of the gelling agent slows down the transfer from one droplet to the other through the aqueous phase. We examined the region where the free diffusion is stopped. i.e., the point where the system changes from the ergodic to the nonergodic state and the kinetics is essentially slowed down. This effect can be balanced by the addition of small amounts of free polymeric stabilizer, which speeds up the kinetics. This is even possible in the case of highly arrested dynamics of the emulsion droplets, as found for the highest KC hydrogel concentrations forming nonergodic system

  1. Predictions of the maximum energy extracted from salinity exchange inside porous electrodes Volume 402, 15 July 2013, Pages 340–349

Journal of Colloid and Interface Science 2013
Impact: 3.532; 38/(136)
DOI: 10.1016/j.jcis.2013.03.068
 M.L. Jiménez,  M.M. Fernández, S. Ahualli, G. Iglesias, A.V. Delgado
Abstract
Capacitive energy extraction based on double layer expansion (CDLE) is the name of a new method devised for extracting energy from the exchange of fresh and salty water in porous electrodes. It is based on the change of the capacitance of electrical double layers (EDLs) at the electrode/solution interface when the concentration of the bulk electrolyte solution is modified. The use of porous electrodes provides huge amounts of surface area, but given the typically small pore size, the curvature of the interface and EDL overlap should affect the final result. This is the first aspect dealt with in this contribution: we envisage the electrode as a swarm of spherical particles, and from the knowledge of their EDL structure, we evaluate the stored charge, the differential capacitance and the extracted energy per CDLE cycle. In all cases, different pore radii and particle sizes and possible EDL overlap are taken into account. The second aspect is the consideration of finite ion size instead of the usual point-like ion model: given the size of the pores and the relatively high potentials that can be applied to the electrode, excluded volume effects can have a significant role. We find an extremely strong effect: the double layer capacitance is maximum for a certain value of the surface potential. This is a consequence of the limited ionic concentration at the particle-solution interface imposed by the finite size of ions, and leads to the presence of two potential ranges: for low electric potentials the capacitance increases with the ionic strength, while for large potentials we find the opposite trend. The consequences of these facts on the possibility of net energy extraction from porous electrodes, upon changing the solution in contact with them, are evaluated.

  1. Dynamic characterization of extremely bidisperse magnetorheological fluids V.: 377 P.: 153-159

Journal of Colloid and Interface Science 2012  ISSN: 0021-9797
Impact: 3.172; 44/(135)
DOI: 10.1016/j.jcis.2012.03.077
Iglesias, GR; Lopez-Lopez, MT; Duran, JDG; Gonzalez-Caballero; Delgado, AV
Abstract
In this work, we investigate the stability and redispersibility of magnetorheological fluids (MRFs). These are disperse systems where the solid is constituted by ferro- or ferri-magnetic microparticles. Upon the application of external magnetic field, they experience rapid and reversible increases in yield stress and viscosity. The problem considered here is first of all the determination of their stability against sedimentation, an essential issue in their practical application. Although this problem is typically faced through the addition of thixotropic agents to the liquid medium, in this work, we propose the investigation of the effect of magnetic nanoparticles addition, so that the dispersion medium is in reality a ferrofluid. It is found that a volume fraction of nanoparticles not higher than 3% is enough to provide a long-lasting stabilization to MRFs containing above 30% iron microparticles. In the, in fact unavoidable, event of settling, the important point is the ease of redispersion of the sediment. This is indirectly evaluated in the present investigation by measuring the penetration force in the suspension, using a standard hardness needle. Again, it is found that the nanoparticles addition produces soft sediments by avoiding short-range attractions between the large iron particles. Finally, the performance of the designed MRFs is evaluated by obtaining their steady-state rheograms for different volume fractions of magnetite and different magnetic field strengths. The yield stress is found to be strongly field-dependent, and it can achieve the high values expected in standard magnetorheological fluids but with improved stability and redispersibility.

  1. Adsorption of Anionic and Cationic Surfactants on Anionic Colloids: Supercharging and Destabilization V.27 N. 15  Pag 9182-9192

Langmuir 2011 ISSN: 0743-7463
Impact: 4.186; 29/(154); 28(134); 30/(232)
DOI: 10.1021/la201242d
Ahualli, S; Iglesias, GR; Wachter, W; Dulle, M; Minami, D; Glatter, O
Abstract
We present herein a study on the adsorption of anionic (SDS), cationic (CTAB), and nonionic (C12E5) surfactants onto anionic silica nanoparticles. The effects of this adsorption are studied by means of the static structure factor, S(q), and the collective diffusion coefficient, D-c, obtained from small-angle X-ray scattering and dynamic light scattering measurements, respectively. The effective charge on the particles was determined also from classical electrophoresis and electroacoustic sonic-amplitude measurements. The surface tension of the sample was also investigated. Of particular note is the adsorption of SDS onto the silica nanoparticles, which leads to supercharging of the interface. This has interesting repercussions for structures obtained by the layer-by-layer (LbL) technique, because emulsions stabilized with supercharged and hydrophobized silica are perfect candidates for use in a multilayer system

  1. Description and performance of a fully automatic device for the study of the sedimentation of magnetic suspensions V. 82 N.: 7 N de artículo: 073906

Review of Scientific Instruments 2011 ISSN: 0034-6748
Impact: 1.367; 20/(58); 60(125)
DOI: 10.1063/1.3609228
Iglesias, GR; Lopez-Lopez, MT; Delgado, AV; Duran, JDG
Abstract
In this paper we describe an experimental setup for the automatic determination of the sedimentation behavior of magnetic suspensions (i.e., disperse systems consisting on ferro- or ferri-magnetic particles in a suitable fluid) of arbitrary volume fraction of solids. The device is based on the evaluation of the inductance of a thin coil surrounding the test tube containing the sample. The inductance L is evaluated from the measurement of the resonant frequency of a parallel LC circuit constructed with the coil and a capacitor of known capacitance. The coil can be moved vertically along the tube at specified steps and time intervals, and from the knowledge of L as a function of the vertical position and time, one can get an image of the particle concentration profiles at given instants of time. The performance of the device is tested against suspensions of spherical iron particles in the micrometer size range dispersed in silicone oil, with various initial concentrations of solids. The sedimentation profiles are then compared with the predictions of existing models for the settling of disperse systems of non-interacting particles

 

 

 

 

  1. Interactions between large colloids and surfactants Volumen: 7 Número: 10 Páginas: 4619-4622

Soft Matter 2011 ISSN: 1744-683X
Impact: 4.390; 27/(134); 28(232); 7/(84); 7/(79)
DOI: 10.1039/c1sm05177f
Iglesias, GR; Wachter, W; Ahualli, S; Glatter, O
Abstract
The interfacial adsorption of an anionic SDS and a nonionic surfactant C(12)E(5), above the cmc onto submicron-sized, negatively charged silica particles in aqueous solution has been investigated by using electrokinetics, conductometry and static light scattering. It was found that both surfactants are prone to being adsorbed onto the silica/water interface. Addition of C(12)E(5) to the silica dispersion leads to a decrease in mobility. This reduced surface charge causes a decrease in the stability of the silica particles. Surprisingly, the addition of SDS brings about an increase in the negative electrophoretic mobility of the anionic silica particles, leading to a supercharging effect. Subsequent addition of C(12)E(5) gives rise to even higher negative electrophoretic mobilities. This unexpected hyper-charging effect can only be understood as a cooperative effect based on mixed micelles of C(12)E(5) and non-adsorbed SDS. Not so unexpectedly, the sequence of surfactant addition was found to be decisive, as quite different results are obtained when C(12)E(5) is added before SDS.

  1. Monoolein: a magic lipid? V. 13 N. 8 P.: 3004-3021

Physical Chemistry Chemical Physics 2011 ISSN: 1463-9076  
Impact: 3.573; 34/(134); 5(33)
DOI: 10.1039/c0cp01539c
Kulkarni, CV; Wachter, W; Iglesias-Salto, G; Engelskirchen, S; Ahualli, S
Abstract
During the last few years, there has been an extraordinary increase in publications describing the manifold applications of monoolein, one of the most important lipids in the fields of drug delivery, emulsion stabilization and protein crystallization. In this perspective we present a comprehensive review of the phase behavior of this 'magic lipid'. An account of various mesophases formed in the presence of water and a collection of formulae for the calculation of their nano-structural parameters are provided. Effects of chemical and biological molecules including lipids, detergents, salts, sugars, proteins and DNA on the classical behavior are also discussed. Physicochemical triggers such as, temperature, pressure and shearing modulate the phase behavior of monoolein self assemblies that are covered in subsequent sections. Finally the growing applications of monoolein in various fields are also reported.

  1. Assessment of surfactant adsorption in oil-based magnetic colloids Adsorption- Volumen: 16 Número: 4-5 Páginas: 215-221

Journal of the International Adsorption Society 2010 ISSN: 0929-5607
Impact: 1.993; 70/(127); 33(135)
DOI: 10.1007/s10450-010-9229-y
Lopez-Lopez, MT; Gomez-Ramirez, A; Iglesias, GR; Duran, JDG; Gonzalez-Caballero, F
Abstract
We describe in this paper different and complementary experimental methods for assessing the adsorption of surfactants on metal particles in oil-based suspensions. Two different kinds of particles are dispersed in mineral oil: iron microparticles and CoNi nanoparticles. The adsorption of oleic acid in the Fe/oil interface in diluted suspensions can be determined by obtaining the adsorption isotherm. In addition, we present a method based on the time evolution of the optical absorbance of suspensions, from which the existence of adsorption can be inferred. For concentrated suspensions, the used of optical methods is not recommended, since they are affected by a significant inaccuracy. We present here a useful alternative based on electromagnetic induction phenomena. The results obtained allow a more comprehensive knowledge of the aggregation process in concentrated suspensions. With the same purpose, a third group of experiments, based on rheological techniques, is carried out in Fe/oil and CoNi/oil concentrated suspensions. In these series of experiments, the effect of three surfactants (oleic acid, aluminum stearate and lecithin) is tested by measuring either the viscosity, or the magnetic field-induced yield stress of the suspensions. The combination of these series of experiments gives us valuable information about the most appropriate surfactant/carrier combination capable of imparting a high stability and a strong magnetorheological response in magnetic colloids.

  1. On the stability of magnetic colloids

Annales UMCS, Chemistry 2008
DOI: 10.2478/v10063-008-0026-3

  1. Stability and flow behavior of a magnetorheological lubricant in a magnetic shock absorber Volumen: 51 Número: 3 Páginas: 271-277

Tribology Transactions 2008 ISSN: 1040-2004
Impact: 0.578; 65/(105)
DOI: 10.1080/10402000701793963
Duran, JDG; Iglesias, GR; Delgado, AV; Ruiz-Moron, LF; Insa, J; Gonzalez-Caballero, F
Abstract
Interest in the use of field-responsive fluids in the automobile industry is growing in view of the increasing capabilities of electronic control in the vehicle's dynamic response. This is the case of magnetorheological fluids or lubricants (MRF). These are capable to change in very short times their rheological behavior upon application of modest magnetic fields. In the present work we describe a new formulation of a stable magnetic fluid that is checked both in a laboratory rheometer and in a commercial shock absorber. It is found that the yield stress can increase by several orders of magnitude when the magnetic field strength reaches a few hundred mT. Furthermore, friction tests carried out in a damper test machine showed that the shock absorber behaved very regularly when charged with the fluid under very different conditions of speed and amplitude of the forced oscillations produced and for various applied magnetic fields.

  1. An experimental method for the measurement of the stability of concentrated magnetic fluids Volumen: 311Número: 2 Páginas: 475-480

Journal of Colloid and Interface Science 2007 ISSN: 0021-9797
Impact: 2.309; 38/(110)
DOI: 10.1016/j.jcis.2007.03.063
Iglesias, GR; Ruiz-Moron, LF; Monesma, JI; Duran, JDG; Delgado, AV
Abstract
In this paper we present a device and method suited to the experimental determination of the sedimentation rate of concentrated suspensions of magnetic particles. The method is based on the measurement of the inductance of one or more sensing coils located at specified positions around a test tube containing the suspension. Such measurement is made possible by the determination of the resonant frequency of a parallel LC circuit in which L is the inductance of the sensing coil and C is the capacity of a capacitor chosen in such a way that the resonant frequency is easily measured. Upon calibration it is possible to relate the resonant frequency to the volume fraction of the particles at the coil location. The method is applied in the present work to the evaluation of the sedimentation kinetics of iron suspensions in base fluids of viscosities ranging from 0.3 to 100 mPas and volume fractions of solids between 2.5 and 25%. Both if a single coil is used and if a set of three coils at different positions are employed, it is possible to detect the rate of accumulation of particles at the bottom of the container as well as a phenomenon of buoyancy of the largest particles brought about by the hydrostatic push of a dense fluid consisting of the smallest particles in the supporting liquid.

  1. Stability of concentrated aqueous clay-magnetite suspensions Volumen: 306 Número: 1-3 Páginas: 150-157

Colloids and Surfaces a-Physicochemical and Engineering Aspects
2007 ISSN: 0927-7757
Impact: 1.601; 58/(110)
DOI: 10.1016/j.colsurfa.2006.12.076
Galindo-Gonzalez, C; Iglesias, GR, Gonzalez-Caballero, F; Duran, JDG
Abstract
This work is devoted to study the sedimentation behavior in concentrated suspensions of magnetite-covered clay particles. These core-shell particles were prepared by adhesion of synthetic magnetite nanoparticles on sodium montmorillonite platelets in aqueous solution at pH 3 and 2 x 10(-3) mol/L NaNO3 ionic strength. A new experimental device, suitable for measuring the time evolution of the local volume fraction in concentrated opaque suspensions of magnetizable particles, is described. The experimental method is based on the variations of the resonant frequency of an oscillating parallel LC circuit in which the coil surrounds a test tube filled with the magnetic suspensions. The sedimentation rate in suspensions with different volume fraction and variable magnetite to clay volume fraction ratio was measured. The results are analyzed considering the effect of both the total energy of interaction between the clay-magnetite (core-shell) particles and the total solid volume fraction of the suspensions. (C) 2007 Elsevier B.V. All rights reserved.

 

 

Patents

 

  • Nº de solicitud: P201631096

Fecha de registro: 12/08/2016
Patente Española
Título: “PAVIMENTO, USO DEL MISMO Y SISTEMA DE SEGURIDAD QUE LO COMPRENDE”
Autores: Fernando Moreno Navarro; Guillermo Ramón Iglesias Salto; María del Carmen Rubio Gámez

  • Nº de solicitud: PCT/ES2014/071002

Fecha de registro: 31/12/2014
Patente PCT
Título: “Ligante modificado con propiedades mecánicas controlables por campos magnéticos”
Autores: Fernando Moreno Navarro; Guillermo Ramón Iglesias Salto; María del Carmen Rubio Gámez

  • Nº de solicitud: PCT/ES2014/070722

Fecha de registro: 25/09/2014
Patente PCT
Título “Dispositivo para medición de energía producida por intercambio iónico”
Autores: Guillermo Iglesias Salto; Silvia Ahualli Yapur; A. V. Delgado; M. L. Jiménez Olivares, L; F. González-Caballero

  • Nº de solicitud: P2013300647

Fecha de registro: 28/06/2013
Fecha de concesión: 13/09/2013
Patente Española
Título: “Amortiguador de fricción basado en elastómeros magnéticos”
Autores: Guillermo Iglesias Salto; J. D. G. Durán; M. López-López; M. Moral; J. Berasategui; I. Aguirre; M. J. Elejabarrieta; M. M. Bou-Ali

  • Nº de solicitud: PCT/ES2013/070443 Nº de patente: WO2014/207268

Fecha de registro: 28/06/2013
Fecha de concesión 31/12/2014
Patente PCT
Título: “Fluido magnetorreológico, método de preparación y amortiguador que lo contiene” o es “Fluidos magnetorreológicos con bimodalidad extrema”
Autores: Guillermo Iglesias Salto; J. D. G. Durán; M. López-López; Silvia Ahualli; Ángel Delgado Mora; Mónica Moral Muñoz

  • Nº de solicitud: P20060235

Fecha de registro: 26/10/2006
Fecha de concesión: 18/11/2009
Cód. de referencia/registro: EPO7119395.7
Patente PCT; Licenciada
Entidad titular de derechos: Repsol.Technology Cente
Título: “Fluido Magnetorreológico (fmr)”
Autores: J. D. G. Durán; F. González-Caballero; A. V. Delgado; Guillermo Iglesias; Salto; M. López-López; M. L. Jiménez Olivares, L; L. Fernández Ruiz-Morón; J. Insa Moneo

 

  • Nº de solicitud: P200700104

Fecha de registro: 29/12/2006
Fecha de concesión: 20/05/2009
Patente Española
Título: “Estructura de relleno con fluidos magnéticos y magnetorreológicos”
Autores: J. D. G. Durán; Guillermo Iglesias Salto; A. V. Delgado; F. González-Caballero; S. Ahualli

  • Nº de solicitud: U200802586    Nº de patente: ES1069470 U

Fecha de registro: 11/12/2008
Fecha de concesión: 01/04/2009
Patente Española
Título: “Muleta o baston amortiguado mediante la variación o cambio de la viscosidad de fluidos magnetorreologicos”
Autores: J. D. G. Durán; Guillermo Iglesias Salto; A. V. Delgado; F. González-Caballero; S. Ahualli

  • Nº de solicitud: U200801685 Nº de patente: ES1069084U

Fecha de registro: 23/07/2008
Fecha de concesión 01/02/2009
Patente Española
Título: “Silla de montar de presión distribuida”
Autores: J. D. G. Durán; Guillermo Iglesias Salto; A. V. Delgado; F. González-Caballero; S. Ahualli

  • Nº de solicitud: P200801895

Fecha de registro: 08/06/2008
Patente Española; Licenciada
Entidad titular de derechos: Repsol.Technology Cente
Título:“Fluido Magnetorreológico”
Autores: J. D. G. Durán; F. González-Caballero; A. V. Delgado; Guillermo Iglesias Salto; M. López-López; L. Fernández Ruiz-Morón; J. Insa Moneo; Romero Palazón E.

  • Nº de solicitud: PCT/ES2007/000266    Nº de patente: WO2007125148 A1 

Fecha de registro: 25/04/2006
Fecha de concesión 08/11/2007
Patente PCT
Título: “FOOTWEAR WITH SHOCK-ABSORBING EFFECT”; “Calzado con Amortiguación”
Autores: J. D. G. Durán; Guillermo Iglesias Salto; A. V. Delgado; F. González-Caballero; S. Ahualli

  • Nº de solicitud: P200502282   Nº de patente: 2284347  

Fecha de registro: 13/09/2005
Fecha de concesión 01/11/2007
Patente PCT
Título: “Método y aparato para la determinación de la velocidad de sedimentación y el perfil de concentración de partículas en fluidos magnéticos y magnetorreológicos”
Autores: J. D. G. Durán; Guillermo Iglesias Salto; A. V. Delgado; F. González-Caballero.


Conferences
1995-2010

Congreso: II International Soft Matter Conference 2010 (5-8 Julio 2010)
Título: Dynamics and Solidifications (Ergodic to Non-Ergodic Transition) In Turbid Soft Material
Autores: Guillermo R. Iglesias , Martin Medebach, Martin Dulle and Otto Glatter
Tipo de participación: Poster. Granada, España.

 

Congreso: II International Soft Matter 2010 (5-8  Julio 2010)

Título: Interactions between Large Colloids and Surfactants
Autores: Guillermo R. Iglesias, Wolfgang Wachter, Otto Glatter
Tipo de participación: Poster. Granada, España.

 

Congreso: II International Soft Matter 2010 (5-8  Julio 2010)

Título: New Light Scattering Instruments for the Measurement of Dynamics in Complex Fluid
Autores: Guillermo R. Iglesias, Martin Medebach, Martin Dulle and Otto Glatter
Tipo de participación: Poster. Granada, España.

 

Congreso: II International Soft Matter 2010 (5-8  Julio 2010)

Título: Nanostructured Water-in-Oil Emulsions with High Water Content Formed Without Stabilizer
Autores: C. V. Kulkarni, Guillermo R. Iglesias and O.Glatter
Tipo de participación: Poster. Granada, España.

 

Congreso: II International Soft Matter 2010 (5-8  Julio 2010)

Título: Effect of Osmotic Gradient on the Morphology of Membrane Protein Crystals Grown In Cubo.
Autores: C. V. Kulkarni, Guillermo R. Iglesias, Oscar Ces, So Iwata and Richard Templer
Tipo de participación: Poster. Granada, España.

 

Congreso: 24º ECIS 2010 (5- 10  Setiembre 2010)
Título: Dynamics and Solidifications (Ergodic to Non-Ergodic Transition) in Turbid Soft Material
Autores: Guillermo R. Iglesias, M.  Medelbach, M. Dulle and O. Glatter
Tipo de participación: Poster. Praga, Rep. Checa.

 

Congreso: 24º  ECIS 2010 (5- 10  Setiembre 2010)

Autores: Guillermo Iglesias-Salto, Chandrashekhar V. Kulkarni , Matija Tomšič, and Otto Glatter
Título: Arrested Dynamics of Structured Nanoparticles using Multi-speckle Light Scattering Technique
Tipo de participación: Poster. Praga, Rep. Checa          .

 

Congreso: 24º  ECIS 2010 (5- 10  Setiembre 2010)

Autores: S. Ahualli, D. Minami, G.R. Iglesias, M. Dulle, O. Glatter
Título: Adsorption of Anionic and Cationic Surfactant on the Surface of Anionic Colloids -Hydrophobization and Supercharging
Tipo de participación: Oral. Praga, Rep. Checa.

2006

 

Congreso: IV Internacional Conference Interfaces Against Pollution. (4-7 Junio 2006)

Título: An experimental method to measure the stability of concentrated colloidal suspensions
Autores: G. R. Iglesias, M. T. López-López, J. D. G. Durán, A. V. Delgado, F. González-Caballero
Tipo de participación: Poster. Granada, España.

 

Congreso: IV Internacional Conference Interfaces Against Pollution. (4-7 Junio 2006)

Título: Study of the stability of concentrated aqueous clay/magnetite suspensions
Autores: C. Galindo-González, G. R. Iglesias, F. González-Caballero, J. D. G. Durán
Tipo de participación: Oral. Granada, España.

 

2004

Congreso: 18º ECIS 2004 (19-24 Septiembre 2004)

Título: Electroptical properties of dilute suspension under DC electric fields
Autores: M.J. Espin, A.V. Delgado, G.Iglesias, F. González-Caballero
Tipo de participación: Oral. Almería, España.

 

1996

Congreso: 81º Reunión  Nacional de Física (13-16 Octubre 1996)

Título: Acelerómetro piezoelctrico
Autores: G.Iglesias, F. Bernardo
Tipo de participación: Poster. Tandil, Argentina.

 

Congreso: 81º Reunión  Nacional de Física. (13-16 Octubre 1996)

Título: Acelerómetro piezoeléctrico para aplicaciones biomecánicas
Autores: V. Correa, G.Iglesias, G. Goroso, E. Bertini, O. Bravo
Tipo de participación: Poster. Tandil, Argentina.

 

Congreso: 81º Reunión  Nacional de Física. (13-16 Octubre 1996)

Título: Modelo de la interacción planta del pie-superficie de apoyo. Aplicación al pie diabético
Autores: G.Iglesias, G. Goroso, O. Bravo
Tipo de participación: Poster. Tandil, Argentina.

 

1995

 

Congreso: 80º Reunión  Nacional de Física (2-6 Octubre 1995)

Título: Acelerómetro
Autores: E. Bertini, G.Iglesias, O. Bravo
Tipo de participación: Poster. Bariloche, Argentina.

 

Congreso: 80º Reunión  Nacional de Física (2-6 Octubre 1995)

Título: Equilibrador electrónico para máquinas rotativas
Autores: G.Iglesias, E. Bertini, O. Bravo
Tipo de participación: Poster. Bariloche, Argentina.

 

Congreso: 80º Reunión  Nacional de Física (2-6 Octubre 1995)

Título: Audiómetro clínico de bajo costo
Autores: R. Garcia, G.Iglesias , E. Bertini, O. Bravo
Tipo de participación: Poster. Bariloche, Argentina.

 

Congreso: 80º Reunión  Nacional de Física (2-6 Octubre 1995)

Título: Plataforma de Fuerza – Aplicaciones biomecánicas
Autores: E. Bertini, G.Iglesias, G. Goroso, O. Bravo
Tipo de participación: Poster. Bariloche, Argentina.