High-performance flexible strain sensors based on silver film wrinkles modulated by liquid PDMS substrates.

Flexible strain sensors based on controllable surface microstructures in film-substrate systems can be extensively applied in high-tech fields such as human-machine interfaces, electronic skins, and soft robots. However, the rigid functional films are susceptible to structural destruction and interfacial failure under large strains or high loading speeds, limiting the stability and durability of the sensors. Here we report on a facile technique to prepare high-performance flexible strain sensors based on controllable wrinkles by depositing silver films on liquid polydimethylsiloxane (PDMS) substrates. The silver atoms can penetrate into the surface of liquid PDMS to form an interlocking layer during deposition, enhancing the interfacial adhesion greatly. After deposition, the liquid PDMS is spontaneously solidified to stabilize the film microstructures. The surface patterns are well modulated by changing film thickness, prepolymer-to-crosslinker ratio of liquid PDMS, and strain value. The flexible strain sensors based on the silver film/liquid PDMS system show high sensitivity (above 4000), wide sensing range (∼80%), quick response speed (∼80 ms), and good stability (above 6000 cycles), and have a broad application prospect in the fields of health monitoring and motion tracking.