A High-Resolution MEMS Capacitive Force Sensor With Bionic Swallow Comb Arrays for Ultralow Multiphysics Measurement

Abstract

Precise force sensing is essential for the mechanical characterization and robotic micromanipulation of biological targets. In this work, a high-resolution MEMS capacitive force sensor was proposed for measuring ultralow multiphysics. A bionic swallow structure that contained multiple feathered comb arrays was designed for reducing chip dimension and eliminating undesirable mechanical cross-coupling effect. The comb structure was optimized for maximum sensitivity, linearity, and compact chip size. Utilizing a novel interconnection configuration, interferences derived from parasitic capacitance and electrostatic forces exerted negligible effects on the sensor output. The proposed bionic force sensor was fabricated following a simple three-mask process and integrated with ASIC readouts. Its measuring sensitivity was 7.151 fF/nm, 0.529 aF/nN, and 4.247 pF/g for displacement, force, and inclination measurements, respectively. The proposed sensor had a large measurement range of 1000.00 nm and 13.83 µN with a high linearity of 0.9998. The 1-σ resolution was 0.0328 nm and 0.4436 nN, and the noise floor resolution was 0.0044 nm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sqrt {{\bm{Hz}}} $</tex-math></inline-formula> and 0.0597 nN/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sqrt {{\bm{Hz}}} $</tex-math></inline-formula> for displacement and force measurements, respectively. The bias stability of Allan deviance was 0.0050 nm and 0.0678 nN at an integration time of 0.65 s. The proposed bionic swallow sensor exhibited considerable improvement over existing capacitive sensors and feasibility for ultralow multiphysics measurement in biomedical applications.