Comb-drive MEMS Oscillators for Low Temperature Experiments

TL;DR

This paper presents the design, fabrication, and characterization of MEMS oscillators capable of operating at very low temperatures, including in superfluid helium, for advanced quantum fluid research.

Contribution

It introduces a novel MEMS resonator design suitable for low temperature environments and demonstrates their functionality down to 0.3 mK in superfluid helium.

Findings

Resonators operate effectively at low temperatures and various pressures.

Surface characterization confirms suitable surface quality for low temperature use.

Resonance properties are well-defined across different fluid regimes.

Abstract

We have designed and characterized micro-electro-mechanical systems (MEMS) for applications at low temperatures. The mechanical resonators were fabricated using a surface micromachining process. The devices consist of a pair of parallel plates with a well defined gap. The top plate can be actuated for shear motion relative to the bottom fixed plate through a set of comb-drive electrodes. Details on the operation and fabrication of the devices are discussed. The geometry was chosen to study the transport properties of the fluid entrained in the gap. An atomic force microscopy (AFM) study was performed in order to characterize the surface. A full characterization of their resonance properties in air and at room temperature was conducted as a function of pressure, from 10 mTorr to 760 Torr, ranging from a highly rarefied gas to a hydrodynamic regime. We demonstrate the operation of our resonator at low temperatures immersed in superfluid 4He and in the normal and superfluid states of 3He down to 0.3 mK. These MEMS oscillators show potential for use in a wide range of low temperature experiments, in particular, to probe novel phenomena in quantum fluids.