Novel Supercapacitor-Based Force Sensor Insensitive to Parasitic Noise

Traditional capacitive sensors suffer from significant parasitic noise when used in liquid environments or inside the human body. The parasitic noise overwhelms the force response of the sensor and makes it very difficult to calculate the absolute force experienced by the sensor. This article focuses on the development of a supercapacitor based force sensor that is immune to parasitic noise. The supercapacitor consists of coplanar electrodes and a solid-state ionic gel electrolyte on a deformable membrane. Force exertion causes deformation of the electrolyte membrane and increases its area of contact with the electrodes, resulting in a change of capacitance. The sensor is sealed, water-proof, and shows absolutely no changes in capacitance when immersed in water or enclosed in extracted sheep tissue. At the same time, its force sensitivity of 0.13 μF/N exceeds the 0.3 pF/N sensitivity of a traditional capacitive sensor by 6 orders of magnitude. The developed sensor could be useful in many biomedical applications where parasitic capacitance is a serious challenge.