Eggshell-inspired membrane—shell strategy for simultaneously improving the sensitivity and detection range of strain sensors

Abstract

The tradeoff between sensitivity and detection range (maximum and minimum stretchability) is a key limitation in strain sensors; to resolve this, we develop an efficient and novel strategy herein to fabricate a highly sensitive and stretchable strain sensor inspired by the membrane–shell structure of poultry eggs. The developed sensor comprises a soft and stretchable surface-grafting polypyrrole (s-PPy) film (acting as the membrane) and a brittle Au film (acting as the shell), wherein both films complement each other at the electrical and mechanical levels. Au forms cracks under strain contributing to its high sensitivity and low detection limit, and s-PPy can bridge Au cracks and increase stretchability which has not been used in strain sensors before. The surface-grafting strategy not only enhances interface adhesion but also tunes the brittle property of native PPy to render it stretchable. Utilizing the synergetic effect of the membrane–shell complementary structure, the strain sensors achieve ultrahigh sensitivity (>107), large stretchability (100%), and an ultralow detection limit (0.1%), demonstrating significant progress in the field of strain sensors. The membrane–shell (Au/s-PPy)-structured strain sensor can successfully detect finger motion, wrist rotation, airflow fluctuation, and voice vibration; these movements produce strain in the range of subtle to marked deformations. Results evidence the ultrahigh performance and bright application prospects of the developed strain sensors.