Root-inspired hierarchical hydrogel-electrode interface enables ultrasensitive sensing.

Ultrasensitive detection of low-frequency and weak-pressure stimuli is crucial for non-invasive wearable physiological signal monitoring, human-machine interfaces, and sonar technologies. Hydrogels, with their low elastic modulus, high conformability, and tunable functionality, have been explored as suitable candidate materials for transduction of such signals. However, conventional hydrogel-based sensors lacking effective interfacial integration or surface engineering are often constrained by weak interfacial adhesion and microstructural fragility, resulting in compromised signal stability. Therefore, overcoming these limitations requires a robust interfacial design that can simultaneously enhance mechanical robustness and stabilize signal transmission. Here, we report a root-inspired hydrogel-electrode interface that integrates dendritic metallic nano-roots interfacial locking and monolithically fabricated microarray architectures. This nano/micro-hierarchical interface synergistically enhances sensing performance through amplified electrical double-layer capacitance, providing an ultralow detection limit of ~0.38 Pa, a gauge factor of 6.0 in the low-pressure region, reliable responses across 50-900 Hz, and stable performance. This strategy offers a versatile approach for realizing robust and ultrasensitive hydrogel-based sensors operating under weak and low-frequency stimuli.