Hydrogel actuators that can undergo structural change upon external stimuli are highly demanded due to their potential applications in diverse fields. However, the actuators based on physically cross‐linked supramolecular hydrogels are largely unexplored. This study reports the engineering of an electrically controllable supramolecular hydrogel as an actuator from a self‐assembling short peptide, in which a catechol moiety is introduced as the stimuli‐responsive motif. This kind of electrochemically responsive hydrogel is mechanically stable and can switch its physical properties dramatically upon the applied electric field. The mechanism and reversibility of the change are studied in detail. As a proof of principle, devices are designed to perform the unidirectional expansion and rotational motion under electrical stimulations. The applications of the actuators for controllable drug release and actuation of microfluidic devices are also illustrated. It is expected that these kind of supramolecular hydrogel actuators can find broad applications as novel biosensors, artificial robots, and smart soft materials.

Using AFM based single-molecule force spectroscopy, we studied the synergy between Dopa and lysine for wet adhesion on titania (TiO2) and mica surfaces.

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Inspired by marine mussela dhesive systems, numerous3 ,4-dihydroxyphenylalanine(DOPA)-containing surface coating materials have been recently designed. It is well known that DOPA has as tronga dhesion ability to different kinds of wet surfaces. However,t he molecular mechanism of DOPAa dhesionr emains elusive. Recent biophysical studies of DOPAa dhesion by both surfacef orce apparatus (SFA) and atomic force microscopy (AFM) suggest that DOPAc an bind to aw ide range of surfaces exhibitingd iverse chemical properties through differentb inding mechanisms. Here, using AFM-based single-molecule force spectroscopy,w es how that even for chemically well-defined crystal surfaces, DOPAc an bind to them by multiple binding modes. The binding forces between DOPAa nd differentr utile TiO 2 surfacesc an vary within ab road range from 40-800 pN at ap ulling speed of 1000nms À1 and are largely dependent on the surface properties. Our findings indicatet hat the local chemicale nvironment can greatly affect DOPAa dhesion, and that single-molecule force spectroscopy is au nique tool to reveal the heterogeneity of DOPAa dhesiont ot he same surface.