Wenhao Shen, J Q Xu, Fan Wang, Qinchuan Li, Jianhua Luo, Ruibin Qi, Cheng Liu, Ke Zhong, Geyu Shao, Jinlei Zhou, Zhifeng Liu, Junhui Zhang, Wei Chen, Geoffrey M. Spinks, Liang Tao, Yuan Yao, Zhen Jiang
Soft actuators that integrate biodegradability, responsiveness to human-safe stimuli, and high actuation performance are highly desirable for next-generation biomedical devices. However, current systems fail to realize these attributes within a single platform. Here, we propose a microfibrillated cellulose (MFC)-based soft actuator incorporating a poly(ethylene glycol) (PEG) network to suppress crystallinity and ionic liquid (IL) aggregation. This design enhances ionic conductivity, forms abundant ion transport channels, and reduces interfacial resistance. Operated at 1 volt, the actuator achieves a record-high energy density of 64.4 kilojoules per cubic meter and the fastest response time of 1 second among reported ionic electroactive polymers (IEAPs) under the same conditions. Such materials are biocompatible and biodegradable in various physiological environments. Device-level demonstrations show that an actuation-enabled sciatic nerve cuff enables high-fidelity signal transmission in vitro with a signal-to-noise ratio of 40 decibels and stable real-time in vivo neural recording with evoked responses of up to ~150 microvolts, supporting minimally invasive bioelectronic interfacing.