Brittle-layer-tuned microcrack propagation for high-performance stretchable strain sensors

High linearity is important for stretchable strain sensors. Herein, we propose a new strategy of brittle-layer-tuned microcrack propagation to achieve high-linearity resistive-type stretchable strain sensors by using a highly facile and effective method. It is achieved by introducing a brittle layer in between the conductive layer and the polymeric substrate followed by a pre-crazing process. A high linearity (R-2 approximate to 0.9721) within 100% strain is achieved, which is an important development for resistance-type stretchable strain sensors. The brittle layer also increases the sensitivity by around three times. Meanwhile, the sensor can be easily patterned and the strong adhesion between the active materials and elastic substrate can be realized through this approach. Then, to demonstrate the feasibility and wide applicability of this brittle layer strategy, PDMS and Ecoflex substrates are employed for the strain sensors preparation. The fabricated sensors exhibit high stretchability up to 100% and high sensitivity with a gauge factor (GF) up to 460.9 based on PDMS. Moreover, an ultrahigh GF value of 41488.8 is obtained by using the Ecoflex substrate. Besides, the working mechanism, reliability and wearable applications are investigated and demonstrated. The superior sensing capabilities of the prepared strain sensors indicate great potential in the fields of integrated stretchable and wearable devices. Our proposed strategy opens up a new perspective to achieve high-performance stretchable strain sensors.