In-Plane and Out-of-Plane MEMS Piezoresistive Cantilever Sensors for Nanoparticle Mass Detection.

Andi Setiono,Alexander Deutschinger,Wilson Ombati Nyang’Au,Michael Fahrbach,Erik Uhde,Maik Bertke,Jiushuai Xu,Ina Kirsch,Ernest J Fantner,Christian H Schwalb,Erwin Peiner,Hutomo Suryo Wasisto

doi:10.3390/s20030618

Abstract

In this study, we investigate the performance of two piezoresistive micro-electro-mechanical system (MEMS)-based silicon cantilever sensors for measuring target analytes (i.e., ultrafine particulate matters). We use two different types of cantilevers with geometric dimensions of 1000 × 170 × 19.5 µm3 and 300 × 100 × 4 µm3, which refer to the 1st and 2nd types of cantilevers, respectively. For the first case, the cantilever is configured to detect the fundamental in-plane bending mode and is actuated using a resistive heater. Similarly, the second type of cantilever sensor is actuated using a meandering resistive heater (bimorph) and is designed for out-of-plane operation. We have successfully employed these two cantilevers to measure and monitor the changes of mass concentration of carbon nanoparticles in air, provided by atomizing suspensions of these nanoparticles into a sealed chamber, ranging from 0 to several tens of µg/m3 and oversize distributions from ~10 nm to ~350 nm. Here, we deploy both types of cantilever sensors and operate them simultaneously with a standard laboratory system (Fast Mobility Particle Sizer, FMPS, TSI 3091) as a reference.

Highlights

Pollutants in the air are often invisible and come from many different sources
An electrothermal piezoresistive cantilever sensor (EtPCS) is designed for in-plane resonant-mode detection. This ElectroThermal Piezoresistive Cantilever Sensor (EtPCS) sensor consists of a heating resistor (HR) and four piezoresistors configured in a Wheatstone bridge (WB), which are intended for mechanical actuation and electrical sensing, respectively [12,19,20]
The HR has a resistance of ~992 Ω, while the four resistors of the WB have resistances of ~803 Ω, ~794 Ω, ~860 Ω, and ~847 Ω

Summary

Introduction

Pollutants in the air are often invisible and come from many different sources. Sulfur dioxide (SO2 ), for instance, is emitted from coal-burning activity in power plants and greatly contributes to the increase of particulate matter (PM), i.e., PM2.5 and PM10. The incomplete combustions of fossil fuels, biofuels, biomass, and black carbon (BC) [1,2] cause the appearance of fine (FPs) or ultrafine particles (UFPs). Since these particles are suspended in the air as aerosols, they may cause serious health problems. The UFP, whose diameter is less than 100 nm, can be deposited in a respiratory tract and enter deep into the lungs, and thereby adversely affect the central nervous and cardiovascular systems [3,4,5] It leads to health problems, e.g., lung diseases, heart

Methods

Discussion

Conclusion