The role of boundary conditions on the free surface of a liquid metal in an electrovortex flow

An electro-vortex flow between two hemispherical electrodes is considered. The influence of the type of boundary condition on the surface of a conducting liquid medium on the velocity field in the volume is studied numerically. The dependences of the velocity on the axis of the vessel on the radius of the small electrode and the parameter of the electric vortex flow are obtained for various types of boundary conditions on the surface.

DESIGN AND MODELING OF A TRIPLE-STEPPED BEAM WITH OUT-OF-PLANE MOTION FOR BISTABLE MICROSWITCH APPLICATIONS

Microswitches have been used for many different applications in building, automation, and security due to requiring little force. A novel design of a triple-stepped beam structure for a mechanical bistable microswitch is presented, and it was found that the bistability of the beam can be achieved by applying an electrostatic force which allows a high deflection with small electrode separation. A finite element method analysis has been used to design the bistable microswitch in a certain range of geometries based on the standard of Taiwan Semiconductor Manufacturing Company (TSMC). The simulation results show that the device requires a verylow input force to get to the bistable stages. The maximum force and the minimum force for switching between the bistable stages are 0.85 mN and 0.23 mN, respectively, which is suitable for electrostatic force at a microscale. The bistability is obtained with the second equilibrium at 75.17 µm that guarantees the perfect contact location between the beam and the conduction path (N+) located at 65.45 µm.

Electrochemical Redox Refrigeration

The high conformational entropy change of the Fe(CN)63−/4− redox reaction can be used as the basis for a compact electrochemical refrigerator. This device is comparable to a liquid version of a Peltier cooler, with two distinct advantages: (1) the entropy change per carrier (1.5 mV/K) of the electrochemical refrigerant is more than 5 times larger than that of state-of-the-art solid thermoelectric materials; and (2) the liquid electrolyte can be advected continuously away from the cooling junction, so that Joule heating in the bulk element does not diminish the delivered cooling effect. In this work, we use infrared microscopy to visualize the thermal aspects of Fe(CN)63−/4− redox, and compare the estimated cooling to calculated values with and without electrolyte flow. While the temperature differences achieved in a single cell are small (~50 mK) and not enhanced by electrolyte flow, the cooling power density (~0.5 W/cm3) is high when normalized to the small electrode volume. Non-dimensional figures of merit are proposed to identify electrochemical redox species for maximizing the cooling effect.

Direct localised measurement of electrical resistivity profile in rat and embryonic chick retinas using a microprobe

We report an alternative technique to perform a direct and local measurement of electrical resistivities in a layered retinal tissue. Information on resistivity changes along the depth in a retina is important for modelling retinal stimulation by retinal prostheses. Existing techniques for resistivity-depth profiling have the drawbacks of a complicated experimental setup, a less localised resistivity probing and/or lower stability for measurements. We employed a flexible microprobe to measure local resistivity with bipolar impedance spectroscopy at various depths in isolated rat and chick embryo retinas for the first time. Small electrode spacing permitted high resolution measurements and the probe flexibility contributed to stable resistivity profiling. The resistivity was directly calculated based on the resistive part of the impedance measured with the Peak Resistance Frequency (PRF) methodology. The resistivity-depth profiles for both rat and chick embryo models are in accordance with previous mammalian and avian studies in literature. We demonstrate that the measured resistivity at each depth has its own PRF signature. Resistivity profiles obtained with our setup provide the basis for the construction of an electric model of the retina. This model can be used to predict variations in parameters related to retinal stimulation and especially in the design and optimisation of efficient retinal implants.