High-Performance Electrochemical Actuator under an Ultralow Driving Voltage with a Mixed Electronic-Ionic Conductive Metal-Organic Framework

Although versatile deformation, high flexibility, and environmental friendliness of electrochemical actuators (EAs) have made them promising in bioinspired soft robots and biomedical devices, the relatively high driving voltages unfortunately impose great restrictions on their applications in low-energy and human-friendly electronics. Here, we find that the uses of a mixed electronic-ionic conductive metal-organic framework (c-MOF), i.e., Ni-3(hexaiminotriphenylene)(2) (Ni-3(HITP)(2)), largely lower the driving voltage of EAs. The as-fabricated EA can work under a driving voltage as low as 0.1 V, representing the lowest value among those for the c-MOF-based EAs reported so far. The Ni-3(HITP)(2)-based EA shows an excellent actuation performance such as a high bending strain difference of 0.48% (+/- 0.5 V, 0.1 Hz) and long-term durability of >99% after 15,000 cycles due to the improved conductivity up to 1000 S<middle dot>cm(-1) and double-layer capacitance as high as 176.3 F<middle dot>g(-1) stemming from the mixed electronic-ionic conduction of Ni-3(HITP)(2).