Design optimization of Miniature Magnetorheological Valves with Self-Sensing Capabilities Used for a Wearable Medical Application

Magnetorheological (MR) fluids are materials characterized as “intelligent” since their rheological properties may be controlled by the excitation of an external magnetic field. The application of the latter brings the fluid from a liquid to a semi-solid state. Due to their properties, these materials are widely used, among others, in biomedical applications. In the present work, multiple MR valves are incorporated as pressure limiters in a smart biomedical insole for diabetic patients. The diabetics are affected by high plantar pressures that cause ulceration and frequently, as a consequence of ulceration, lower extremity amputation. This novel insole aims at the active plantar pressure offloading. Thus, considering the small size of the insole, the number of the valves, as well as the high plantar pressures that reach up to 1 MPa on diabetic feet, a study is performed on optimizing the design of the MR valve, exploiting the Design of Experiments (DoE) techniques. Moreover, a testbench is presented for the examination of pressure self-sensing capabilities of the valves, with a future goal to integrate them in the design optimization and acquire a sensorless system.

Preliminary Study of Pressure Self-Sensing Miniature Magnetorheological Valves

Yoan René Cyrille Civet, Minh Trung Duöng, Kenny Jeanmonod, Sofia Lydia Ntella, Yves Perriard

Magnetorheological (MR) valves have been included in many innovative engineering systems, such as dampers, clutches, or brakes, with different fields of application. Their role serves actuation purposes, while integrated displacement and velocity sensing in the actuators has been studied, as well. In this paper, we present the working principle, design, and preliminary results of a miniature MR valve with pressure self-sensing capabilities that exploits the electromagnetic induction phenomenon. The valve can work in a pressure range from 200 kPa to 700 kPa, supplied by a current of a maximum 0.3 A. The suggested valve design is realized with two coils, one for the current application and the magnetic field creation and one for the sensing of the electromagnetic induction. A specially designed test-bench, that facilitates MR fluid flow and pressure regulation, was used for the experimental procedures.

IEEE2021

Heterogeneous Integration of Low Power pH FinFET sensors with Passive Capillary Microfluidics and miniaturized Ag/AgCl quasi-Reference Electrode

Francesco Bellando, Erick Antonio Garcia Cordero, Hoël Maxime Guérin, Mihai Adrian Ionescu, Amira Muhech Medrano

This work presents one of the first low power pH sensing microfluidic chip based on the heterogeneous integration of: (i) high-k FinFET sensors with liquid gate, (ii) miniaturized Ag/AgCl quasi-Reference Electrode and (iii) passive microfluidic. The integration of these three components provides a fully integrated and compact platform that could be exploited for ionic monitoring in biofluids for healthcare applications. We describe the full fabrication process for the microfluidic system with the embedded reference electrode. The electrical characterization of heterogeneously integrated pH FinFET sensor with the integrated reference electrode shows Id-Vg characteristics with subthreshold swing SS~141mV/dec, low Ioff current and ION/IOFF > 105. When applying a constant current operation scheme, a sensitivity of 8mV/pH of the output drain voltage is reported. Due to the biocompatibility of the selected materials and small size, the resulting microsystem-on-chip could be used as a noninvasive wearable sensor for continuous monitoring of pH in sweat.

Ieee2016

A quantum magnetic analogue to the critical point of water

Kazimierz Conder, Ellen Fogh, Julio Antonio Larrea Jiménez, Frédéric Mila, Bruce Normand, Henrik Moodysson Rønnow, Ludger Weber, Mohamed Zayed

At the liquid-gas phase transition in water, the density has a discontinuity at atmospheric pressure; however, the line of these first-order transitions defined by increasing the applied pressure terminates at the critical point(1), a concept ubiquitous in statistical thermodynamics(2). In correlated quantum materials, it was predicted(3) and then confirmed experimentally(4,5) that a critical point terminates the line of Mott metal-insulator transitions, which are also first-order with a discontinuous charge carrier density. In quantum spin systems, continuous quantum phase transitions(6) have been controlled by pressure(7,8), applied magnetic field(9,10) and disorder(11), but discontinuous quantum phase transitions have received less attention. The geometrically frustrated quantum antiferromagnet SrCu2(BO3)(2) constitutes a near-exact realization of the paradigmatic Shastry-Sutherland model(12-14) and displays exotic phenomena including magnetization plateaus(15), low-lying bound-state excitations(16), anomalous thermodynamics(17) and discontinuous quantum phase transitions(18,19). Here we control both the pressure and the magnetic field applied to SrCu2(BO3)(2) to provide evidence of critical-point physics in a pure spin system. We use high-precision specific-heat measurements to demonstrate that, as in water, the pressure-temperature phase diagram has a first-order transition line that separates phases with different local magnetic energy densities, and that terminates at an Ising critical point. We provide a quantitative explanation of our data using recently developed finite-temperature tensor-network methods(17,20-22). These results further our understanding of first-order quantum phase transitions in quantum magnetism, with potential applications in materials where anisotropic spin interactions produce the topological properties(23,24) that are useful for spintronic applications.

2021

A quantum magnetic analogue to the critical point of water

Kazimierz Conder, Ellen Fogh, Julio Antonio Larrea Jiménez, Frédéric Mila, Bruce Normand, Henrik Moodysson Rønnow, Ludger Weber, Mohamed Zayed

2021