High-performance silicon nanocomposite based ionic actuators

Abstract

Ionic actuators are promising candidates for artificial intelligence by virtue of their fast response and large strain under a low voltage stimulus. However, their actuation performances were limited to inferior ion-sensitive materials and electrodes with rather low mass loading (∼1 mg cm⁻²). Thicker electrodes with higher mass loading increase ion diffusion limitations during the electrochemical process and hence reduce the utilization of active materials without fully expressing the actuation effect. Here, a highly ion-sensitive silicon nanocomposite with a hierarchical porous structure is designed for ionic actuators. According to ex situ cryogenic TEM results, this material exhibits a large volume strain of 310% at the microscale under a voltage of 0.8 V in a three-electrode system. Additionally, its highly interconnected architecture facilitates rapid ion/electron transport and thus reduces the ion penetration depth across the thickness direction in electrodes. The actuator with a mass loading of 9 mg cm⁻² delivered impressive actuation performances, including a wide frequency response from 1 to 20 Hz, superfast response speed within 210 ms, a high blocking force of 71 mN, a large energy density of 10.91 kJ m⁻³, and excellent cycling stability over 10 000 cycles. Furthermore, a meso-mechanical model is put forward to verify actuation performances and displays great potential for prediction of advanced actuation materials.