Existing ionic artificial muscles still require a technology breakthrough for much faster response speed, higher bending strain, and longer durability. Here, we report an MXene artificial muscle based on ionically cross-linked Ti3C2Tx with poly(3,4 ethylenedioxythiophene)-poly(styrenesulfonate), showing ultrafast rise time of within 1 s in DC responses, extremely large bending strain up to 1.37% in very low input voltage regime (0.1 to 1 V), long-term cyclic stability of 97% up to 18,000 cycles, markedly reduced phase delay, and very broad frequency bandwidth up to 20 Hz with good structural reliability without delamination under continuous electrical stimuli. These artificial muscles were successfully applied to make an origami-inspired narcissus flower robot as a wearable brooch and dancing butterflies and leaves on a tree as a kinetic art piece. These successful demonstrations elucidate the wide potential of MXene-based soft actuators for the next-generation soft robotic devices including wearable electronics and kinetic art pieces.

In this study, high-performance ionic soft actuators are developed for the first time using collectively exhaustive boron and sulfur co-doped porous carbon electrodes (BS-COF-Cs), derived from thiophene-based boronatelinked covalent organic framework (T-COF) as a template. The one-electron deficiency of boron compared to carbon leads to the generation of hole charge carriers, while sulfur, owing to its high electron density, creates electron carriers in BS-COF-C electrodes. This antagonistic functionality of BS-COF-C electrodes assists the charge-transfer rate, leading to fast charge separation in the developed ionic soft actuator under alternating current input signals. Furthermore, the hierarchical porosity, high surface area, and synergistic effect of co-doping of the BS-COF-Cs play crucial roles in offering effective interaction of BS-COF-Cs with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), leading to the generation of high electro-chemomechanical performance of the corresponding composite electrodes. Finally, the developed ionic soft actuator based on the BS-COF-C electrode exhibits large bending strain (0.62%), excellent durability (90% retention for 6 hours under operation), and 2.7 times higher bending displacement than PEDOT:PSS under extremely low harmonic input of 0.5 V. This study reveals that the antagonistic functionality of heteroatom co-doped electrodes plays a crucial role in accelerating the actuation performance of ionic artificial muscles.

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