https://hdl.handle.net/10481/6827 2026-04-08T16:29:55Z https://hdl.handle.net/10481/112661 Optimized agarose-based conductive hydrogel electrodes for capacitive deionization Naranjo, David; Lirio Piñar, Juan Antonio; Amir, Umamah; Rodríguez García, Julia; García Torres, José María; Iglesias, Guillermo R.; Delgado, Ángel V.; Armelin, Elaine; Ahualli Yapur, Silvia Alejandra; Torras, Juan The development of advanced electrode materials is critical for improving the efficiency and durability of capacitive deionization (CDI) technologies for water desalination and separation processes. In this work, a novel conductive hydrogel based on agarose (Aga), tannic acid (TA), and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was designed, optimized, and evaluated as a functional coating for CDI electrodes. The hydrogel formulation was systematically optimized by varying the TA and PEDOT:PSS contents, identifying an optimal composition containing 10 wt% TA and 20 wt% PEDOT:PSS. This formulation exhibited a favorable combination of mechanical robustness, high porosity (∼93%), well-distributed pore size, preserved swelling capacity, and enhanced electrochemical properties. Electrochemical characterization revealed improved cathodic stability and capacitive behavior, supporting enhanced ion storage and transport. When implemented in CDI cells, the hydrogel-coated electrodes demonstrated significantly enhanced salt adsorption capacity and higher charge efficiency compared to conventional activated carbon (AC) electrodes. Although the initial salt adsorption capacity was slightly lower than that of other soft-coated electrodes, the gel-based system showed progressive performance improvement and superior long-term cycling stability during aging tests. The enhanced hydration, facilitated ion transport, and sustained structural integrity contributed to improved operational efficiency and durability. Overall, the proposed Aga-TA-PEDOT:PSS hydrogel represents a promising electrode material for energy-efficient, stable, and scalable CDI systems, with potential applications in low-salinity and brackish water treatment. https://hdl.handle.net/10481/112559 Field-induced alignment dynamics in suspensions of polarizable rods Zerón Jiménez, Iván Michael; Iturbe-Jabaloyes, Álvaro; Escañuela Copado, Adri; Moncho Jordá, Arturo; Patti, Alessandro Fluids composed of polarizable particles exhibit tunable structural and functional properties when subjected to external electric fields, as the particles tend to reorient and align along the field direction. This field-induced anisotropy leads to pronounced changes in macroscopic properties, rendering these systems highly relevant for applications in nanotechnology. Understanding the dynamics of their response to external fields is crucial for designing responsive materials with fast and controllable actuation. In this work, we employ molecular simulation to study the behavior of suspensions of polarizable rod-like particles under the action of a uniform electric field, with particular attention to the transient dynamics associated with the switching on and off of the field. Induced dipoles are modeled by independently varying charge magnitude and field strength, yielding a variable effective polarizability. The induced dipole moment of each rod is treated as an effective, externally controlled parameter, and collective polarization effects arising from local electric fields generated by neighboring particles are not explicitly included. The system is studied in a dense regime, where interparticle interactions play a significant role and are implicitly controlled via pressure. We investigate how the characteristic response time depends on the competition between thermal motion and electric forces across a range of temperatures and field strengths. Our results reveal a rich dynamical behavior: at low to moderate field intensities, increasing the temperature significantly reduces the response time, as thermal agitation facilitates reorientation. However, beyond a criti cal field strength, the response time plateaus, becoming effectively temperature-independent. This saturation indicates a regime where the aligning torque from the field dominates over thermal fluctuations, setting a lower bound for how fast the system can respond. More specifically, we show that the alignment dynamics cannot be inferred from single-particle behavior alone, but emerge from a nontrivial interplay of field-induced dipolar torques, thermal fluctuations, and steric interactions at finite density, producing strongly temperature-dependent and nonlinear trends in both the nematic order parameter and response times. I.M.Z. and A.P. acknowledge grant P21 00015 funded by Junta de Andalucía, Consejería de Universidad, Investigación e Innovación. A.J.I. was supported by Banco Santander and the University of Granada through the P5A: Research Initiation Scholarship Program for Students (Grant No. ACG265/6a). A.P. and A.M.-J. acknowledge project grant PID2022-136540NB-I00 awarded by MICIU/AEI/10.13039/501100011033 and ERDF, A Way of Making Europe. A.E.-C. and A.P. acknowledge Grant W911NF-23-1-0099 awarded by the U.S. Army Research Office. A.P. has been supported by a María Zambrano Senior fellowship, financed by the European Union within the NextGenerationEU program and the Spanish Ministry of Universities. All authors gratefully acknowledge the UGR Servicio de Supercomputación and PROTEUS, the supercomputing center of the Institute Carlos I for Theoretical and Computational Physics, for providing computational resources. Valuable discussions with María L. Jiménez and Miguel Ibáñez, both from the University of Granada, are also sincerely appreciated. https://hdl.handle.net/10481/112201 Life-like processes in synthetic protocells under external fields Willems, Vivien; Moreno Reolid, Pablo; Fojo, José; Rodríguez Arco, Laura; Álvarez, Laura Synthetic protocells are self-assembled compartments designed to reproduce minimal features of prebiotic boundaries through bottom-up assembly. They offer a controlled platform to isolate universal physicochem ical principles relevant to both origins-of-life studies and life-like soft materials. Despite improved control over composition and architecture, most current protocells remain weakly dissipative and near reversible in contrast to living cells sustained by continuous nonequilibrium fluxes. Because autonomous energy trans duction is often absent, external fields are used to actuate compartments and induce life-like functions. This perspective reviews field-responsive protocells and analyzes how light, electric, and magnetic inputs couple to material properties to generate morphological transitions, transport, and adaptive responses. We intro duce a classification of actuation regimes and a framework to separate passive forced behavior from genuine nonequilibrium internal state changes. We further outline strategies to quantify state variables, fluxes, and dissipation and propose hybrid designs coupling external actuation with internal energy transduction for adaptive, multiresponsive protocells. https://hdl.handle.net/10481/111493 Magnetorheology of Bimodal Fluids in the Single−Multidomain Limit Morillas Medina, José Rafael; Bombard, Antonio J F; Vicente Álvarez-Manzaneda, Juan De In this manuscript we investigate the shear rheology, sedimentation stability and redispersibility characteristics of bimodal MR fluids with a large-to-small size ratio σL/σS ≈ 100 where the small-size population of particles is in the single−multidomain limit (σS ≈ 100 nm) to promote the formation of core−shell supraparticles (i.e., large particles surrounded by the smaller ones). We focus on the effect of mixing the two kinds of particles in different proportions while keeping either the large particle volume fraction or the total volume fraction constant. Five different nanoparticles, having different chemical compositions and shapes, are investigated in this work: barium ferrite, magnetite, iron, chromium dioxide, and goethite. The results demonstrate that nanoparticles fill the voids between microparticles, and this locally enhances the magnetic field. The on-state yield stress and effective enhancement may increase or decrease depending on the magnetization of the nanoparticles as compared to that of the microparticles. An enhanced MR effect is experimentally observed and also simulated with finite element methods, when the magnetization of the nanoparticles is larger than that of the microparticles. Bimodal MR fluids exhibit better penetration and redispersibility response than the monomodal counterparts and dimorphic magnetorheological fluids based on nanofibers. This work was supported by the MINECO MAT 2016-78778- R and PCIN-2015-051 projects (Spain), European Regional Development Fund (ERDF), and by the Junta de Andalucía P11-FQM-7074 project (Spain). J.R.M. acknowledges a FPU14/01576 fellowship. A.J.F.B. is grateful for FAPEMIG grants ETC-00043-15, PEE-00081-16, and APQ-01824-17 (Brasil). https://hdl.handle.net/10481/111487 On the importance of interchain interaction and rotational contribution to the computation of the yield stress in magnetorheology Morillas Medina, José Rafael; Vicente Álvarez-Manzaneda, Juan De