A Capacitive MEMS Viscometric Sensor for Affinity Detection of Glucose

This paper presents a capacitively based microelectromechanical systems affinity sensor for continuous glucose monitoring (CGM) applications. This sensor consists of a vibrating Parylene diaphragm, which is remotely driven by a magnetic field and situated inside a microchamber. A solution of poly(acrylamide-ran-3-acrylamidophenylboronic acid) (PAA-ran-PAAPBA), a biocompatible glucose-sensitive polymer, fills the microchamber, which is separated from its surroundings by a semipermeable membrane. Glucose permeates through the membrane and binds reversibly to the phenylboronic acid moiety of the polymer. This results in a viscosity change of the sensing solution, causing a detectable change in the Parylene diaphragm vibration which can be measured capacitively. Experimental results demonstrate that the device is capable of detecting glucose at physiologically relevant concentrations ranging from 30 to 360 mg/dL. The response time of the sensor to glucose concentration changes is approximately 1.5 min, which can be further improved with optimized device designs. Excellent reversibility and stability are observed in sensor responses, as highly desired for long-term CGM.