Impedius: A Signal-Space Multiplexing Technique Using Individual Elements of Impedance for Chained Passive Sensors
Bhaskar Dutt, Yixuan Chen, Daniel Ashbrook, Valkyrie Savage
TEI 2025

Commercial touch input devices sense changes in capacitance (C), resistance (R), and inductance (L), but aggregate these into a single, complex quantity: impedance. Commercially available LCR meters, however, can report the individual elements of impedance. We use this capability to introduce Impedius, a signal-space multiplexing technique. With Impedius, we create and sense multiple static values and continuous changes in the R and C values within a single circuit by manipulating capacitance and resistance individually. Further, we explore 3D printing as a method to create predictable resistance and capacitance values via geometric and printer setting manipulation, and offer a software tool that generates components with desired R and C values. Based on 96 samples, our printed passive components have error μ = 4.63 pF, σ = 1.68 pF (capacitors) and μ = 13.85 kΩ, σ = 5.59 kΩ (resistors). We demonstrate multiple interactive example applications with our components, highlighting the opportunities for signal-space multiplexing.