A variable stiffness adhesive enabled by joule heating effect

Smart adhesives have attracted great attention due to their reversible adhesion capacities and stimuli-responsive adhesion behavior. However, for most reported smart adhesive materials, it remains challenging to combine high conductivity, tunable adhesion, thermal healing, tunable mechanical strength, recyclability and reusability into one material. Herein, a new smart adhesive material composed of supramolecular polymer and graphene nanoplates was successfully designed and prepared. Strong and recycle adhesion performance was realized on various surfaces, with a maximum adhesion strength of 6.48 MPa on glass. In addition to excellent adhesion recyclability and reusability, this composite adhesive exhibits high mechanical strength, excellent plasticity and thermal healing properties. Through Joule heating effects, we can not only switch the adhesive between on and off states, but also tune the adhesion strength in a wide range. Based on these features, we designed a simple electric gripper which can raise and drop various objects simply by changing the applied voltages.