Elastomer-Based Pneumatic Switch for Radio Frequency Microdevices

This paper reports the realization and characterization of a pneumatic microswitch integrated with a high-frequency radio frequency (RF) transmission line on an elastomer substrate. A process for the fabrication of low-loss RF coplanar transmission lines on flexible elastomeric polydimethylsiloxane (PDMS) substrates was developed, and devices realized using this process were used to determine the characteristics of PDMS as an RF substrate with uniform low loss and low dielectric constant being measured. To demonstrate the capabilities of this elastomer-based RF platform, a micromechanical switch exploiting a pneumatic membrane valve was integrated with the PDMS RF transmission line. Repeatable switching was observed with greater than 20-dB suppression in the “off” state and minimal degradation of the transmission line characteristics in the “on” state being achieved over a multioctave 2-20-GHz bandwidth. These valve-integrated transmission lines had an insertion loss of 0.16 dB·mm^-1 at 20 GHz. This proof-of-concept device represents a novel combination of the areas of micropneumatics, flexible electronics, and broadband microwave devices with excellent RF properties, low interference, bias-free pneumatic switching, and relatively simple fabrication.