High-Performance Multifunctional Flexible Strain Sensors Based on Plant Leaf-Inspired Hierarchical Micropore Structures

Abstract

Wearable flexible strain sensors have shown great potential in fields such as medical health, motion monitoring, and human-computer interaction. Developing flexible strain sensors that possess excellent comprehensive performance and a simple manufacturing process remains a great challenge at present. Inspired by the numerous stomata of aquatic plant leaves in nature, here we propose a simple, efficient, and low-cost technique to fabricate flexible strain sensors with hierarchical micropore structures. The hierarchical micropores can effectively control stress distribution and guide crack propagation and termination on heterogeneous film surfaces, resulting in a network-like structure composed of many short, discontinuous crack segments. This feature endows the sensor with excellent comprehensive performances, including high sensitivity (up to 12138), a wide detection range (50%), a low detection limit (0.01%), fast response/recovery (108/97 ms), and outstanding durability (20,000 cycles). Such a high-performance sensor can accurately monitor various human activities such as pulse beating, microexpression, swallowing, joint bending, and vocalization by throat or loudspeaker vibration. Morse code-based information expression and encrypted transmission of complex information have been achieved by using a single or three bidirectionally bendable sensors. This work provides a facile strategy for fabricating high-performance sensors through biomimicry of plant leaves, demonstrating broad application prospects in wearable devices, electronic skins, soft robots, and information interactions.