Development of low frequencies, insulating thick diaphragms for power MEMS applications

TL;DR

This paper presents a novel design of thick, low-frequency insulating diaphragms for power MEMS, utilizing fluid-structure interaction to achieve thermal insulation and mechanical compliance with simple planar geometries.

Contribution

It introduces an analytical model and experimental validation for fluid-structure based insulating diaphragms, enabling low-frequency operation in microthermal engines.

Findings

The model accurately predicts experimental results.

The proposed design achieves low resonant frequencies.

A dimensionless model aids in designing hybrid fluid structures.

Abstract

Major challenges of micro thermal machines are the thermal insulation and mechanical tolerance in the case of sliding piston. Switching from piston to membrane in microengines can alleviate the latest and lead to planar architectures. However, the thermal isolation would call for very thick structures which are associated to too high resonant frequencies which are detrimental to the engine performances. A thermal and mechanical compromise is to be made. On the contrary, based on fluid structure interaction, using an incompressible fluid contained in a cavity sealed by deformable diaphragm it would be possible to design a thick, low frequency insulating diaphragm. The design involves a simple planar geometry that is easy to manufacture with standard microelectronics methods. An analytical fluid structure model is proposed and theoretically validated. Experimental structures are realized and tested. The model is in agreement with the experimental results. A dimensionless model is proposed to design hybrid fluid structures for micromachines.