Electrical Double-Layer based Wearable Tensile and Pressure Sensors: Optimizing Materials and Architecture for Improved Sensing Response

Abstract

The development of wearable electronics requires a higher understanding of the structural parameters that enable selective mechanical sensing across different deformation modes. In this work, we present a materials-to-architecture framework for multifunctional iontronic textile sensors based on thermoplastic polyurethane (TPU) and the ionic liquid (IL) -butyl-3-methylimidazolium thiocyanate [Bmim][SCN]. By systematically incorporate different IL contents from 0 to 60 wt.%, the sample incorporating 40 wt.% displayed the optimal balance between ionic conductivity and long-term environmental stability by preventing IL surface migration. When processed as dense films, the TPU/[Bmim][SCN] (TIL) enables linear strain sensing (S = 0.58). Conversely, the integration of both TPU and IL [Bmim][SCN] into a porous neoprene scaffold (N-TIL) creates an interface that amplifies the effective electrochemical double layer (EDL) effect, yielding a six-fold increase in pressure sensitivity (1.8 × 10⁻² kPa⁻¹). Electrochemical impedance spectroscopy (EIS) confirms that the architectural transition from dense to porous reduces interfacial resistance and introduces additional Maxwell–Wagner–Sillars interfaces. A glove prototype was developed to demonstrate the sensor ability to detect joint flexion from fingertip pressure by matching the sensor architecture to the specific stimulus.