Analysis of a hybrid micro-electro-mechanical sensor based on graphene oxide/polyvinyl alcohol for humidity measurements

In this paper, we present a redundant microsensor based on the bulk and etch silicon-on-insulator (BESOI) process for measuring relative humidity (RH), by using a graphene-oxide/ polyvinyl-alcohol (GO/PVA) composite. The MEMS is a mechanical oscillator, composed of a proof mass with multilayer of nanomaterials (GO/PVA) and suspended by four crab-leg springs. The redundant approach realized concerns the use of different readout strategies in order to estimate the same measurand RH. This is an intriguing solution to realize a robust measurement system with multiple outputs, by using the GO/PVA as functional material. In the presence of RH variation, GO/PVA (1) changes its mass, and as consequence, a variation of the natural frequency of the integrated oscillator can be observed; and (2) varies its conductivity, which can be measured by using two integrated electrodes. The sensor was designed, analyzed and modeled; experimental results are reported here to demonstrate the effectiveness of our implementation.