Hervé Fanet’s research while affiliated with Université Grenoble Alpes and other places

We report the simulation, design, fabrication and performance assessment of capacitive MEMS, carrying out contactless electromechanical computing with ultra-low-power consumption. The novel concept is implemented on silicon using on-purpose differential comb-drive actuators. This shift in the paradigm allows near-zero power dissipation by asymptotically suppressing static and dynamic energy losses which are inherently present in current hardware for logic implementation. Furthermore, this novel approach based on capacitive information encoding allows recovery of the invested charges by the power supply asymptotically suppressing dynamic losses and opening the way towards adiabatic operation. At the very least, the contactless operation resolves the reliability issues in existing electromechanical logics based on N/MEMS relays.

We report the first experimental proof of concept of a new electromechanical adiabatic logic family operating without any kind of electrical and mechanical contacts. Based on comb-drive actuators and standard microelectromechanical system (MEMS) microfabrication, we demonstrate the cascadability of logic gates up to 170 °C, and operation in the kilohertz-range under a power supply of 4.5 V. Assuming that state-of-the-art microfabrication can downscale our MEMS gates by a factor of 100, we expect a dissipation of 0.1 aJ/op (24 kBT) at 250 kHz at 45 mV. This study paves the way toward new reliable low-power electromechanical digital circuits.

A system including first and second electric or electronic circuits galvanically isolated from each other, and a coupling device coupling the first circuit to the second circuit, the coupling device including a variable-capacitance capacitor including first and second electrodes mobile with respect to each other, separated by an insulating region, and third and fourth electrodes electrically insulated from the first and second electrodes, capable of receiving a control signal to vary, by an electrostatic, electromagnetic, or piezoelectric actuation mechanism, the relative position of the first and second electrodes, to vary the capacitance between the first and second electrodes.

A logic cell including a fixed assembly including a first electrode, a mobile assembly including a second electrode, and third, fourth, and fifth electrodes, wherein: the first, second, third, fourth, and fifth electrodes are insulated from one another; the first and second electrodes define a capacitor variable according to the position of the mobile assembly relative to the fixed assembly; the third electrode is connected to a node of application of a first logic input signal; the fourth electrode is connected to a node of application of a second logic input signal; the fifth electrode is connected to a reference node; and the position of the second electrode relative to the first electrode is a function of a combination of the first and second logic input signals.

This paper reports the study, design, and simulation of a symmetrical comb-drive actuator. The approach for definition of the potential energy of the system is proposed. The electrical parameters of the comb-drive actuator are defined in COMSOL Multiphysics® software. Depending on an actuation voltage and an initial design it can form system with one, two, and three stable states. We show that the equilibrium at x = 0 is more stable for the comb-drive actuator with positive overlap than for device with the gap of the same value. The proposed approach will be used for design of the symmetrical actuator, which forms the output of the recently proposed contactless four-terminal MEMS element for capacitive adiabatic logic based on silicon MEMS technology.

A variable - capacitance capacitor having first and second electrodes mobile with respect to each other and third and fourth electrodes insulated from the first and second elec trodes , capable of receiving a control signal to vary the relative position of the first and second electrodes in order to vary the capacitance between the first and second electrodes , the capacitor further including a system for controlling the position of the second electrode with respect to the first electrode , the system being arranged so that , for at least one relative position of the second electrode with respect to the first electrode , the position of the second electrode with respect to the first electrode is independent from the voltage between the first and second electrodes .