A Low Spring Constant Piezoresistive Microcantilever for Biological Reagent Detection

Abstract

This paper introduces a piezoresistive microcantilever with a low spring constant. The microcantilever was fabricated with titanium (Ti) as the piezoresistor, a low spring constant polyimide (PI) layer, and a thin silicon oxide (SiO2) layer as the top and bottom passive layers, respectively. Excellent mechanical performances with the spring constant of 0.02128 N/m and the deflection sensitivity (∆V/V)/∆z of 1.03 × 10−7 nm−1 were obtained. The output voltage fluctuation of a Wheatstone bridge, which consists of four piezoresistive microcantilevers, is less than 3 μV@3 V in a phosphate buffered saline (PBS) environment. A microcantilever aptasensor was then developed through functionalizing the microcantilevers with a ricin aptamer probe, and detections on ricin with concentrations of 10, 20, 50 and 100 ng/mL were successfully realized. A good specificity was also confirmed by using bovine serum albumin (BSA) as a blank control. The experiment results show that the Ti and PI-based microcantilever has great prospects for ultrasensitive biochemical molecule detections with high reliability and specificity.

A Flexible PI/Si/SiO2 Piezoresistive Microcantilever for Trace-Level Detection of Aflatoxin B1

“…The IgG detection limit was 10 ng/mL [ 31 ]. In 2020, our group proposed a low spring-constant polyimide(PI)-based microcantilever biosensor, which consisted of a four-fold titanium piezoresistor and a PI passivation layer [ 32 ]. For titanium, the resistance change is mainly caused by dimension change; thus, the deflection sensitivity is usually lower than singlecrystal silicon as the piezoresistive material.…”

Editorial for the Special Issue on MEMS and Microfluidic Devices for Analytical Chemistry and Biosensing

“…In [1], Yuan Tian et al report on a novel MEMS microcantilever biosensor fabrication process which does not rely on expensive and potentially fragile SOI wafers. The novel design uses titanium as piezo-resistor between two thin Polyimide and SiO 2 passive layers, featuring a comparatively low spring constant.…”