Adaptable thermoresponsive polymer for long-term electrical coupling in plant electrophysiology monitoring

Electrophysiological signals provide valuable insights into plant health, facilitating measures to enhance crop productivity. Despite advances in measurement methods, long-term (>1 day) acquisition techniques remain limited, hindering continuous monitoring. Current long-term techniques rely on invasive electrodes, as noninvasive electrodes fall short in operational duration and conformability. Here, a capacitively coupled electrode with an adaptable coupling layer is developed for noninvasive, month-long electrophysiological monitoring on diverse plants. The adaptable coupling layer is formed by in situ sol-gel transition, followed by dehydration of thermoresponsive hydrogel on plants, achieving high conformability to complex surfaces and stable electrical coupling. For 1 month on trichome-covered plant surfaces, the electrode maintains a high signal-to-noise ratio comparable to a gold-standard noninvasive electrode, which typically lasts a few hours. Long-term monitoring reveals drought-specific signal features that correlate with plant water status. Physiological investigations indicate an essential role of calcium and reactive oxygen species, highlighting the potential of our electrode in generating biological insights and inspiring plant sensing innovations.