A gradient-structured ionic bimodal sensor with a giant piezoionic and thermal-resistive effect for crosstalk-free pressure–temperature perception

Abstract

Pressure–temperature sensors based on ionogels show significant potential for mimicking the complex sensing functions of human skin. However, they suffer from crosstalk because the ionic conductivity or resistance signal is sensitive to both temperature and pressure. Herein, to address this issue, a gradient-structured ionic sensor with the combination of piezoionic and thermal-resistive effects was designed as a bimodal sensor to monitor the temperature and pressure without crosstalk. The piezoionic-induced self-generated potential responds exclusively to pressure, whereas another resistance component within the sensor is primarily sensitive to temperature, owing to its specific design. Furthermore, it demonstrates a high voltage signal of ∼200 mV in piezoionic response, surpassing most of the conventional piezoionic materials. Meanwhile, the bimodal sensor exhibits an outstanding temperature-sensing response with a relatively high sensitivity of −3.54%/°C. Crosstalk investigations reveal that the sensor enables independent pressure sensing within 0–348 kPa at 30–50 °C and crosstalk-free temperature detection under 0–49 kPa. Additionally, this sensor exhibits rapid self-healing capability. Owing to these advantages, the bimodal sensor can independently monitor pressure and temperature stimuli, and evaluate the softness of materials, showcasing its potential in robotic tactile sensing.