A Plant-Wearable Salinity Sensor for Dynamic Monitoring of Salt Transport

Real-time and in situ monitoring of salt transport in plants is highly important for agricultural production. However, traditional salinity sensors struggle to detect the salinity of soft plant surfaces such as leaf and root surface. In this study, a flexible potentiometric sensor with high sensitivity was developed for the detection of soil, root, and leaf surfaces salinity. The sensor uses copper hexacyanoferrate as the cation-selective electrode material and Ag/AgCl as the anion-selective electrode material to build a flexible bipolar system and incorporates a hydrogel as a micro reaction pool for redox reactions. Benefiting from the hydrogel reaction pool, the sensor can work in ambient conditions and exhibits superior characteristics for salinity detection, including wide salinity range (1–100 ppt), high resolution (<1 ppt), wide pH range (4–10), low relative humidity (RH) (>33% RH), good reproducibility, and stability. The sensors have achieved nondestructive monitoring of salt transport within soybean plants via in situ measurements of the salinity of leaf surface, root surface, and soil. Flexible potential salinity sensors have wide application prospects in dynamic plant monitoring and other fields.