Novel Supercapacitor-Based Force Sensor Insensitive to Parasitic Noise

Abstract

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 impossible 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 co-planar electrodes and a solid state ionic gel electrolyte on a deformable membrane. Force exertion causes deformation of the electrolyte membrane, increases its area of contact with the electrodes, resulting in a change of capacitance. The sensor is sealed, waterproof, 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 μ F/N exceeds the 0.3 pF/N sensitivity of a traditional capacitive sensor by 6 orders of magnitude. The developed sensor could have many biomedical applications in which parasitic capacitance is a serious challenge.

Commercial supercapacitor parameter estimation from step voltage excitation

“…Concepts from fractional calculus were employed since the supercapacitors model includes a CPE. These findings are important for the employment of supercapacitors in various industrial applications and show that in addition to other available techniques, supercapacitor parameters can be estimated accurately from their measured response to a step voltage. This is particularly important when the voltage switching happens faster or close to the internal time constant of the device τ .…”

First Decade of Interfacial Iontronic Sensing: From Droplet Sensors to Artificial Skins

“…The structure design for the sensors based on film format, which is also derived from the membrane deformation, is similar to the one based on droplet format. [102,153,186] According to Equation (2), the sensitivity of the sensor has a positive correlation with its geometrical shape, that is, the length and width of the sensing membrane. Meanwhile, the height of the spacer, which can be recognized as the thickness of the chamber in droplet format, and the thickness of the sensing membrane show a negative relationship with the sensors' sensitivity.…”

“…In particular, both the parasitic influences along the transmission line and the electromagnetic noises (typically within a range of µF cm −2 ) from the ambient environment became negligible from substantial. [99,100,102] Moreover, it also offered high noise immunity, high spatial definition, and responses to both static and dynamic stimuli in addition to its unique optical transparency. Since then, development of the iontronic sensing had been accelerated.…”

An Instrumented Urethral Catheter With Supercapacitor Based Force Sensor

“…The discontinuity in the material at the edge of a capacitor results in additional radial components in the electric field, called the fringe electric field, which in turn generate parasitic capacitance components on the sides of a capacitor. In a supercapacitor, due to the thin dielectric layer and high surface area electrodes, the capacitance of a supercapacitor is at least 3 orders of magnitude higher than the parasitic capacitance in a supercapacitor, which makes the parasitic capacitance negligible [9].…”

“…pollute the sensor signal. The parasitic capacitance for in vivo use is of the order of femto or pico Farads according to previous research of our group ( [3,8,9]) and is hard to eliminate by estimation and subtraction.…”