From Network to Channel—Crack-Based Strain Sensors with High Sensitivity, Stretchability and Linearity via Strain Engineering

High-performance stretchable strain sensors are indispensable for mechanical deformation detection in electronic skin applications such as health monitoring and human-robot interfaces. Thus far, achieving a stretchable strain sensor with a high sensitivity that works linearly over a wide working range is still a great challenge. Among various applicable working mechanisms of strain sensors, crack-based strain sensors have the advantages of flexible material selection, easy fabrication, and high sensitivity. Here, we propose a universal strain engineering strategy that introduces an inhomogeneous spatial distribution of stress, which results in a distinguished crack density distribution in space and a critical state of crack propagation behavior between network and channel morphologies. By controlling the occurrence of the critical state, strain sensors are capable to perform high sensitivity, stretchability, and linearity simultaneously. The strain sensors can be tuned to realize a gauge factor of 690.95 in a linear working range of 0-40% (<i>R</i>² = 0.993) or a gauge factor of 113.70 in a larger linear working range of 0-120% (<i>R</i>² = 0.999). Intraocular pressure monitoring has been demonstrated based on these sensors to show their great application potential.