Intelligent Monitoring System for Plant Growth Based on the PAM-Li-Zn Ionic Hydrogel

Abstract With the rapid advancement of flexible electronics and smart agriculture, plant wearable sensors have attracted increasing attention for precision agricultural monitoring. However, conventional rigid sensors suffer from mechanical incompatibility with soft plant tissues and invasive attachment, limiting long-term in situ monitoring. Here, a flexible triboelectric nanogenerator (TENG) sensor based on a conductive ionic hydrogel (PAM-Li-Zn TENG) was developed and integrated with a Bluetooth module for wireless plant monitoring. The hydrogel composed of PVA, AM, LiCl, and zinc chloride provided excellent flexibility, ionic conductivity, and water retention. The optimized hydrogel containing 3 wt % glycerol exhibited a tensile strength of approximately 124 kPa and an elongation at break of nearly 582%. With PDMS encapsulation, the sensor achieved structural stability and reliable operation. Combined with machine learning algorithms, the PAM-Li-Zn TENG enabled intelligent identification of plant growth states and abiotic stress monitoring, generating an open-circuit voltage of 312 V and a short-circuit current of 31 μA under 50 N force at 1.6 Hz.