Hierarchical Porous Biowaste-Based Dual Humidity/Pressure Sensor for Robotic Tactile Sensing, Sustainable Health, and Environmental Monitoring

A crucial tradeoff between material efficacy and environmental impact is often encountered in the development of high-performance sensors. The use of rare-earth elements or intricate fabrication techniques is sometimes needed for conventional sensing materials, posing concerns regarding sustainability. Exploring the potential of tomato peel (TP) as a dual-purpose sensing dielectric layer for pressure and humidity monitoring is a paradigm shift, capitalizing on its porous structure and hygroscopic nature. TP-based humidity sensor (TP-HS) exhibits impressive results, with a wide humidity sensing range (5%–95%), fast response/recovery time (6.5/9 s), a high sensitivity (12 500 pF %RH⁻¹), and a high stability (30 days). Additionally, TP-based pressure sensor (TP-PS) also shows excellent performance in accurately sensing pressure changes in a wide range (0–196 kPa). TP-HS can easily distinguish between breathing rates (normal, fast, and slow) and moisture content present in different moisturizers (aloe vera and sanitizer) along with its successful use for proximity sensing. Alternatively, TP-PS demonstrates weight measurement (490 and 980 N), grip recognition (measuring the pressure exerted by each finger), and gesture detection (by monitoring multiple bending angles 0°, 30°, 50°, and 80°). A wearable, biocompatible dual sensor based on a promising sustainable material for environmental, robotic, and health monitoring applications is successfully demonstrated.