Design of Low-Cost Ultrasensitive Polymer-Based ITO Piezoresistive BioMEMS Cantilever Sensor to Detect Heavy Metal Ions in Water

Abstract

This letter focuses on the design and simulation of a polymer-based piezoresistive microcantilever for the detection of heavy metal ions (HMIs) in water. The proposed cantilever uses the SU-8 2005 polymer as a structural material to simplify fabrication while enhancing deflection and sensitivity. Indium tin oxide (ITO) is employed as the primary piezoresistive layer, replacing conventional polysilicon, which requires complex ion-implantation processes. The significant piezoresistive coefficient of ITO ($-6.72 \times 10^{-3} \, \text{MPa}^{-1}$) ensures high sensitivity to pressure variations, while its compatibility with low-temperature deposition techniques further reduces the complexity of the fabrication. The cantilever, with dimensions of $300 \times 100 \, \mu \text{m}$, was modeled and simulated using COMSOL Multiphysics under an applied boundary load of $32.68 \, \text{Pa}$ and a constant terminal voltage of $3\text{ V}$ to achieve 1–100 $\mathrm{\mu }$g/L limit of detection specifications to detect HMIs. From the results of the designed cantilever, the sensitivity is calculated as $51.965 \, \mu \Omega /\Omega /\text{Pa}$ for the multiarm device. This work highlights the potential of polymer-based microelectromechanical systems for cost-effective and scalable environmental monitoring applications, offering a novel approach to toxic HMIs detection in water.