Persona: Rubio Álvarez, Miguel Ángel
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Rubio Álvarez
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Miguel Ángel
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Publicación Linear shear rheology of aging β-casein films adsorbing at the air/water interface(Elsevier, 2018-02-01) Martínez Pedrero, F.; Sánchez Puga, Pablo; Chulia Jordan, R.; González Rubio, Ramón; Tajuelo Rodríguez, Javier; Ortega Coloma, Francisco Javier; Rubio Álvarez, Miguel ÁngelIn this work, the viscoelasticity of fragile β-casein films has been followed using different macro- and microrheological techniques. The modulus of the complex surface viscosity varies with time, allowing for the monitoring of the protein adsorption and annealing. β-casein adsorption creates a soft glassy gel at the interface that experiences an aging process. Macrorheological experiments with multiple probe sizes in addition to microrheological experiments demonstrated the consistency of the surface rheological properties over a broad range of viscosities. Surface pressure measurements were performed to complement the characterization of the processes.Publicación BiconeDrag—A data processing application for the oscillating conical bob interfacial shear rheometer(Elsevier, 2019-06) Sánchez Puga, Pablo; Pastor Ruiz, Juan Manuel; Tajuelo Rodríguez, Javier; Rubio Álvarez, Miguel ÁngelBiconeDrag is a software package that allows one to perform a flow field based data processing of dynamic interfacial rheology data pertaining to surfactant laden air–fluid interfaces obtained by means of a rotational bicone shear rheometer. MATLAB and Python versions of the program are provided. The bicone fixture is widely used to transform a conventional bulk rotational rheometer into an interfacial shear rheometer. Typically, such systems are made of a bicone bob, which is mounted on the rheometer rotor, and a cylindrical cup. Usually, the experiment consists of measuring the response of the interface under an oscillatory stress. The program takes the values of the torque/angular displacement amplitude ratio and phase difference to compute the interfacial dynamic moduli (or complex viscosity) by consistently taking into account the hydrodynamic flow both at the interface and the subphase. This is done by numerically solving the Navier–Stokes equations for the subphase velocity field together with the Boussinesq–Scriven boundary condition at the interface, and no slip boundary conditions elsewhere. Furthermore, the program implements a new iterative scheme devised by solving for the complex Boussinesq number in the rotor’s torque balance equation.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 ÁngelDevelopments 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.