# Design of Acetaldehyde Gas Sensor Based on Piezoelectric Multilayer Microelectromechanical System Resonator

## TL;DR

This paper presents a low-cost, fast-response acetaldehyde gas sensor using a piezoelectric MEMS resonator for detecting low concentrations of the harmful compound.

## Contribution

The novelty lies in the design of a cost-effective MEMS-based acetaldehyde sensor with a piezoelectric multilayer resonator and linear detection capability.

## Key findings

- The sensor has a first bending frequency of 4722.4 Hz and a sensitivity of 8.22 kHz/g.
- It can detect acetaldehyde concentrations as low as 102 ppm with linear frequency shifts.
- Analytical and FEM models show good agreement in predicting the sensor's mechanical behavior.

## Abstract

Acetaldehyde is a volatile organic compound that can cause damage at the cellular and genomic levels. The monitoring of acetaldehyde gas at low concentrations requires fast-response and low-cost sensors. Herein, we propose the design of an acetaldehyde gas sensor based on a low-cost Microelectromechanical System (MEMS) process. This sensor is formed by a single-clamped piezoelectric multilayer resonator (3000 × 1000 × 52.2 µm) with a simple operating principle and easy signal processing. This resonator uses a zinc oxide piezoelectric layer (1 µm thick) and a sensing film of titanium oxide (1 µm thick). In addition, the resonator uses a support layer of 304 stainless steel (50 µm thick) and two aluminum layers (100 nm thick). Analytical and Finite-Element Method (FEM) models are developed to predict the mechanical behavior of the gas sensor, considering the influence of the different layers of the resonator. The analytical results agree well with respect to the FEM model results. The gas sensor has a first bending frequency of 4722.4 Hz and a sensitivity of 8.22 kHz/g. A minimum detectable concentration of acetaldehyde of 102 ppm can be detected with the proposed sensor. This gas sensor has a linear behavior to detect different acetaldehyde concentrations using the frequency shifts of its multilayer resonator. The gas sensor design offers advantages such as small size, a light weight, and cost-efficient fabrication.