Persona:
Tajuelo Rodríguez, Javier

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jtajuelo@ccia.uned.es
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0000-0002-4085-7610
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Tajuelo Rodríguez
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Javier
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2013 - 201982020 - 20259
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Mostrando 1 - 10 de 17
  • Miniatura
    Publicación
    Propiedades mecánicas de monocapas de Langmuir con reómetro interfacial de aguja
    (Universidad Nacional de Educación a Distancia (España). Facultad de Ciencias, 2013-07-16) Tajuelo Rodríguez, Javier; Rubio Álvarez, Miguel Ángel; Pastor Ruiz, Juan Manuel; Martínez Pedrero, Fernando
  • Miniatura
    Publicación
    Phase transitions of untilted fatty-acid Langmuir monolayers during isobaric heating and cooling: Interfacial rheology results
    (American Physical Society, 2025-08-13) Sánchez Puga, Pablo; Tajuelo Rodríguez, Javier; Martínez Pedrero, Fernando; Ortega Francisco; Rubio Álvarez, Miguel Ángel
    We study the two-dimensional melting of fatty acid Langmuir monolayers via the mechanical properties of their untilted phases, compact solid (CS), solid (S), and superliquid (LS). Taking the dynamic moduli as order parameters in isobaric temperature sweeps of behenic and arachidic acid monolayers, the CS-S and S-LS transitions appear as continuous transitions. However, a discontinuity appears in a high-order crossed susceptibility that involves the derivative of the dynamic moduli with respect to the control parameter (temperature). The critical value of the shear storage modulus at the melting temperature agrees with the prediction of the KTHNY theory, but the characteristic exponent does not.
  • Miniatura
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    Reología Interfacial. Técnicas macro y microscópicas y su aplicación a la caracterización de monocapas de Langmuir
    (Universidad Nacional de Educación a Distancia (España). Escuela Internacional de Doctorado. Programa de Doctorado en Ciencias, 2017) Tajuelo Rodríguez, Javier; Pastor Ruiz, Juan Manuel; Rubio Álvarez, Miguel Ángel
    En esta memoria se aborda el diseño y desarrollo de técnicas experimentales para la caracterización de las propiedades reológicas de cizalla de sistemas cuasi-bidimensionales formados en interfases fluido-fluido, y su posterior aplicación en el estudio de la dependencia de los módulos dinámicos superficiales de monocapas de Langmuir de ácidos grasos respecto de dos de las variables termodinámicas del sistema, la temperatura y la presión superficial. En el momento del inicio del presente trabajo existían en la bibliografía diversas técnicas con similares objetivos, surgidas de manera continua a partir de mediados del s. XX. La influencia de las propiedades mecánicas de los sistemas interfaciales en multitud de procesos biológicos o industriales ha generado un creciente interés en esta rama científica, alentando la aparición de métodos experimentales cada vez más refinados. A pesar de este creciente esfuerzo, la medida de las propiedades mecánicas de sistemas con un espesor típico del orden de nanometros, formados en interfases y, por tanto, en contacto con al menos una fase líquida, es aún hoy un tema abierto. De hecho, los resultados obtenidos por medio de diferentes técnicas que, en función de su longitud característica, podemos clasificar en técnicas micro y macro-reológicas, son en muchos casos difícilmente comparables. El objetivo principal de la primera parte de esta memoria, en la que se describen los trabajos de diseño y construcción de los dispositivos experimentales y formulación de los modelos teóricos empleados, es, en primer lugar, refinar el funcionamiento del macro- Reómetro Interfacial de Aguja Magnética (ISR) mediante el empleo de sondas más pequeñas y ligeras que incrementan su resolución. Esta novedad introducida en la técnica, junto con un correcto tratamiento de la hidrodinámica del sistema, nos permite extender el rango de aplicación de este dispositivo a viscosidades superficiales mucho menores, haciendo posible la comparación directa con técnicas micro-reológicas. A partir de los conocimientos y experiencia adquiridos durante la ejecución de esta tarea, que se desarrolla en el Capítulo 1, abordamos en el Capítulo 2 el diseño y construcción de un nuevo ISR basado en el movimiento controlado de una trampa magnética formada por dos pequeños imanes. Gracias a este nuevo método de accionamiento, la importancia relativa de la resistencia hidrodinámica debida a la interfase aumenta significativamente, incrementando, así mismo, la resolución del dispositivo. En el Capítulo 3 aplicamos a una geometría distinta, el Reómetro Interfacial de disco cónico, una aproximación numérica análoga a la empleada en los capítulos anteriores para obtener el campo de velocidades en la subfasae y la interfase. La técnica macro-reológica de disco cónico está ampliamente extendida gracias a su versatilidad, puesto que está basada en un reómetro de torsión convencional adaptado para poder medir reología de cizalla en interfases mediante una geometría de sencilla construcción. Proponemos un nuevo esquema, basado en la resolución numérica del campo de velocidades, para obtener los módulos dinámicos superficiales a partir de los datos recogidos por el reómetro de torsión (par ejercido y ángulo girado), y comparamos los resultados obtenidos a través de dicho esquema con aquellos presentes en la bibliografía. Ello nos permite, de paso, establecer bajo qué condiciones la resolución numérica del campo de velocidades es necesaria para una correcta interpretación de los resultados. En la segunda parte de la memoria empleamos el ISR de trampa magnética en el estudio de la Reología Interfacial de monocapas de Langmuir de ácidos grasos. Las propiedades micro-estructurales de estos sistemas han sido ampliamente estudiadas durante las últimas tres décadas, pero el conocimiento sobre sus propiedades mecánicas es mucho menor, probablemente debido a las dificultades de esta rama científica mencionadas anteriormente. En el Capítulo 4 se presentan los resultados de un estudio pormenorizado de la dependencia de los módulos dinámicos respecto de la presión superficial y la temperatura de la monocapa, construyendo en última instancia un diagrama de fases a partir de la información obtenida en los experimentos reológicos.
  • Miniatura
    Publicación
    Shear rheology of fluid interfaces: Closing the gap between macro- and micro-rheology
    (Elsevier, 2018-09) Guzmán Solís, Eduardo; Pastor Ruiz, Juan Manuel; González Rubio, Ramón; Tajuelo Rodríguez, Javier; Rubio Álvarez, Miguel Ángel; Ortega Coloma, Francisco Javier
    For many years the determination of the shear viscosity of interfacial layers has been source of strong controversy. This is mainly because different techniques provided different values of such parameter, which leads in many cases to a puzzling interpretation of the experimental results. One possible explanation of this is the non-correct analysis of the hydrodynamic conditions of the measurement and, in particular, the assumption of some approximations that may not be necessarily valid in all cases. The introduction of hydrodynamic consideration in the study of interfacial shear rheology has helped to clarify some of the existing discrepancies between measurements performed using different devices, thus allowing one to establish clearly the viscosity range in which different techniques can operate with enough sensitivity for determining the interfacial shear viscosity. This review puts in perspective the most recent developments on the studies of the interfacial shear rheology of fluid/fluid interfaces, analyzing the strength and weakness of the different approaches.
  • Miniatura
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    Combined thermodynamic and time-resolved structural analysis of interactions between AP2 and biomimetic plasma membranes provides insights into clathrin-mediated endocytosis
    (Nature Research, 2025-08-12) Maestro, Armando; Zaccai, Nathan R.; González Martínez, Juan F.; Sánchez Puga, Pablo; Tajuelo Rodríguez, Javier; Rubio Álvarez, Miguel Ángel; Santa María, Andreas; Carrascosa Tejedor, Javier; Pereira, Daniel; Montesinos Marín, Idelfonso; Gutfreund, Philipp; Campbell, Richard; Kotar, Jurij; Kelly, Bernard T.; Cicuta, Pietro; Owen, David J.
    Clathrin-mediated endocytosis (CME), the main mechanism for swift, selective protein uptake in eukaryotic cells, initiates with adaptor protein AP2 recruitment to the plasma membrane (PM). AP2 recognizes PM-associated PtdIns(4,5)P2 and protein cargo for internalization. Nonetheless, many aspects of this process remain unclear due to their in vivo complexity. Here, a thermodynamic and time-resolved structural analysis of AP2 binding to different biomimetic PM was undertaken under physiological conditions using a combination of neutron reflectometry, interfacial tensiometry and rheology, and atomic force microscopy. The resultant in vitro data replicated previous in vivo observations, as well as yielded biophysical insights into normal and aborted CME. The presence of cargo may not be pivotal for the “activating” conformational change of AP2. However, the presence of cargo extends AP2’s residence time on the membrane surface, due to slower on- and off-rates, thereby tentatively giving sufficient time for CME to proceed fully. Moreover, upon interaction with AP2, phospholipid lateral diffusion decreases markedly, inducing a gel phase attributed to creating a percolated network involving AP2 on the membrane, which could potentially serve as a mechanism for modulating subsequent clathrin binding. The subsequent clathrin polymerization at the membrane is dependent on the AP2’s clathrin binding sequence.
  • Miniatura
    Publicación
    Flow field based data processing for the oscillating conical bob interfacial shear rheometer
    (American Institute of Physics, 2018-01-01) Pastor Ruiz, Juan Manuel; Tajuelo Rodríguez, Javier; Rubio Álvarez, Miguel Ángel
    A rotational rheometer can be used as an interfacial shear rheometer (ISR) by means of proper accessories that allow one to shear fluid-fluid interfaces in a controlled manner. One of the most used accessories, even commercially available, is based on a biconical bob geometry. However, recovering the correct values of the rheological variables is far from trivial. A strategy that has proved to be successful in other ISRs is to properly account for the interface and subphase drags by numerically finding the corresponding flow fields and, then, use an iterative scheme to recover the proper values of the complex Boussinesq number and, consequently, the dynamic surface moduli. Here, we propose to use such a scheme for the biconical bob oscillatory rheometer. We compare our solution with different well known previous approximations, and discuss under which conditions those approximations may lead to errors in the data processing. We have tested the performance of our design and numerical framework on several interfacial systems, comparing the results to those obtained through a magnetic needle rheometer (ISR). We demonstrate that, even for relatively low values of the Boussinesq number, the numerical flow field solution here proposed allows one to precisely reproduce the results obtained by the ISR, while those approximations based on a linear velocity decay at the interface may introduce spurious effects on the calculation of the dynamic surface moduli.
  • Miniatura
    Publicación
    A numerical model for the simulation of complex planar Newtonian interfaces
    (Elsevier, 2025-01) Esteban Paz, Adolfo; Hernández Rodríguez, Julio; Tajuelo Rodríguez, Javier; Rubio González, Miguel Ángel
    We present a numerical model for the simulation of complex planar interfaces at which moving solid objects can be immersed, reproducing a wide variety of experimental conditions. The mathematical model consists of the Navier-Stokes equations governing the incompressible viscous flow in the liquid subphase, the transport equation for the evolution of the surfactant concentration at the interface, and the interfacial stress balance equation. The equations are simplified by treating the problem as isothermal and the surfactant as insoluble. The bulk flow equations are discretized using a collocated finite volume method, while the interfacial flow equations are discretized using a finite area method. The Boussinesq-Scriven interface constitutive model and a variant form accounting for extensional viscosity are used to describe the extra surface stress tensor. The coupling between surfactant concentration, interfacial velocity, and bulk velocity is treated implicitly by solving the interfacial and bulk equations sequentially at each time step until a stopping criterion is satisfied. The motion of the solid is treated by an arbitrary Lagrangian- Eulerian method. The model has been implemented in the OpenFOAM framework and allows the incorporation of new interface models and solvers, making the developed new package a versatile and powerful tool in the field of computational rheology. Applications of the model include the numerical simulation of flow around objects, such as probes, immersed at a complex interface, reproducing given experimental conditions, and its use as a tool in the analysis and design of interfacial stress rheometers. Several test cases have been performed to validate the model by comparing the results obtained with analytical solutions and with numerical and experimental results available in the literature.
  • Miniatura
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    Enhancing magnetorheology with precession magnetic fields
    (American Institute of Physics, 2022-01-01) Terkel, Matthew; Tajuelo Rodríguez, Javier; de Vicente, Juan
    We demonstrate a new route to enhance magnetorheology using precession-like magnetic fields. This field configuration is generated by the superposition of a 2D rotational field applied orthogonal to a uniaxial DC field. Maintaining a columnar linear chain structure when applying a precession field was determined to be integral in increasing the average cluster size of the aggregates for low precession angles and a low Mason number. A yield stress increase was experimentally observed when reapplying a uniaxial DC field following the application of a controlled low-angle precession field indicating a favorable structural evolution had taken place under the unsteady field configuration. Experimental results of small-amplitude oscillatory shear tests and shear rheograms are supported by particle-level simulation 3D models and start-up tests.
  • Miniatura
    Publicación
    Flow field-based data analysis in interfacial shear rheometry
    (Elsevier, 2021-02) Sánchez Puga, Pablo; Pastor Ruiz, Juan Manuel; Tajuelo Rodríguez, Javier; Rubio Álvarez, Miguel Ángel
    Developments in interfacial shear rheometers have considerably improved the quality of experimental data. However, data analysis in interfacial shear rheometry is still an active field of research and development due to the intrinsic complexity introduced by the unavoidable contact of the interface with, at least, one supporting bulk subphase. Nonlinear velocity profiles, both at the interface and the bulk phases, pervade the system dynamical behavior in the most usual experimental geometries, particularly in the case of soft interfaces. Such flow configurations demand data analysis schemes based on the explicit calculation of the flow field in both the interface and the bulk phases. Such procedures are progressively becoming popular in this context. In this review, we discuss the most recent advances in interfacial shear rheology data analysis techniques. We extensively review some recently proposed flow field-based data analysis schemes for the three most common interfacial shear rheometer geometries (magnetic needle, double wall-ring, and bicone), showing under what circumstances the calculation of the flow field is mandatory for a proper analysis of the experimental data. All cases are discussed starting at the appropriate hydrodynamical models and using the equation of motion of the probe to set up an iterative procedure to compute the value of the complex Boussinesq number and, from it, the complex interfacial viscosity or, equivalently, the complex interfacial modulus. Moreover, two examples of further extensions of such techniques are proposed, concerning the micro-button interfacial shear rheometer and the potential application of interfacial rheometry instruments, together with adapted flow field-based data analysis techniques, for bulk rheometry, particularly in the case of soft samples.
  • Miniatura
    Publicación
    iRheoFoam: A package for simulating complex planar interfaces
    (Elsevier, 2025-02-10) Esteban Paz, Adolfo; Hernández Rodríguez, Julio; Tajuelo Rodríguez, Javier; Rubio Álvarez, Miguel Ángel; Agencia Estatal de Investigación (España)
    The numerical simulation of the flow around a rigid object, such as a probe, placed at a complex interface to reproduce certain experimental conditions is a useful tool for the analysis and design of interfacial stress rheometers. To perform such simulations, we have developed iRheoFoam, an open-source package implemented in the OpenFOAM framework. It is based on the Boussinesq–Scriven constitutive law and the Navier–Stokes equations, includes various solvers for both time-dependent and steady problems, and allows easy incorporation of new interface models and solvers, making it a versatile and powerful tool