Recyclable flexible pressure, temperature, and humidity multimodal sensors based on micro-pyramidal structures and PVA/Choline Chloride/Ethylene Glycol

Abstract

Flexible sensors are a commonplace wearable electronic device. The development of flexible sensors that can detect multiple signals and are recyclable is necessary to meet the requirements of practical wearability and environmental friendliness. This paper reports a recyclable flexible pressure, temperature, and humidity multimodal sensor based on micro-pyramidal structures and polyvinyl alcohol (PVA), choline chloride (ChCl), ethylene glycol (EG) material systems (MPCE-sensor). PVA/ChCl/EG (PCE) films with micro-pyramidal structures were prepared using a template-assisted transfer process and an evaporative solvent method, and the sensors were obtained by assembling the structural faces of the two films face-to-face. The sensor exhibits a high pressure sensitivity (13.49 kPa^-1), a rapid response time (39 ms), and remarkable durability (5000 cycles). The sensor has a temperature sensitivity of -5.95%/°C (30-40 °C) and can detect subtle temperature changes. Furthermore, the high water absorption capacity of PVA endows the sensor with exceptional humidity sensing capabilities, achieves a fast humidity response time of 2.1 s and a sensitivity of 4.71 MΩ/%RH. More interestingly, the sensing material exhibits excellent recyclability. It dissolves in water and the solution is used to reprepare the sensing material (repeated five times). The sensor can also be used to detect breathing status and recognize speech, enabling applications in real-time health monitoring and human-computer interaction.