Triple mode and multi-purpose flexible sensor fabrication based on carbon black and thermoplastic polyurethane composite with propolis

Abstract

This study reports the design, fabrication, and application of strain and tactile sensors molded with Carbon Black (CB)/Thermoplastic Polyurethane (TPU) composite ink into flexible-soft 3D printed TPU substrate. In sensor design, three different geometries, namely Straight Line/Zigzag/Wavy, are produced to investigate the effect on the sensing behavior. 3D printed molds are preferred due to their low cost and simplicity in fabrication. Additionally, propolis, which is antibacterial and has therapeutic properties for wound and fungal diseases, is added to the composite material to benefit its healing and protective properties. The sensing properties of propolis are investigated for its use as mixing and coating materials. According to electrical characterization, the fabricated structures can be used in triple mode as piezoresistive, piezocapacitive, and piezoinductive sensors. The gauge factor (GF) values for sensors using different ratios of materials varies between 3 and 10. Given conventional metallic strain gauges whose GF is typically around 2, the obtained GF values are remarkable. The distribution of the applied stress on the sensor surface is given by simulations. In addition, the characteristic changes of the samples according to the frequency are examined, and equivalent circuits are provided.