Single-input single-output multi-touch soft sensor systems using band-pass filters

In many soft sensor systems, external wires for connecting the sensors to control circuits have posed practical problems, in terms of compact form factors and physical robustness. This study proposes a design of soft sensor arrays that can operate with a drastically reduced number of wires without degrading the original performance. The proposed concept is an array of soft sensing modules, each of which consists of an inductor and a capacitor embedded next to the resistive sensing module, constructing a resistor-inductor-capacitor band-pass filter. By adjusting the values of the capacitance and the inductance, unique frequency band is assigned to each sensing module, enabling the distinctive detection using only two external wires regardless of the number of modules. The multi-touch sensing functionality of the system is analytically modeled and experimentally characterized. Taking advantage of the design, a fingertip tactile sensor and an insole foot pressure sensor are demonstrated as practical applications.