Universal Anipulation of Macro-To-Microobjects by Controlling Adhesion of Nanotip Shape Memory Polymer Surface

Shape memory polymer (SMP) possesses the capability to undergo dynamic variations in stiffness when subjected to external stimuli such as heat or light. It exhibits the unique ability to be shape-fixed into desired shapes and can revert to its original from through the shape memory effect. Exploiting these attributes, SMP serves as smart adhesives in applications like soft grippers and transfer printing, providing a solution to challenges posed by the adhesion paradox, a feature distinct from traditional elastomer adhesives.<br/>Here, we report a nanotip SMP surface with extreme reversible adhesion, demonstrating its adeptness in manipulating objects across a spectrum ranging from macro-scale (≥10cm) to micro-scale (≥5μm). This innovative approach leverages the distinctive features of SMP to effectively resolve challenges related to the adhesion paradox, while also capitalizing on the adhesion paradox through a return to the original rough surface, thereby achieving excellent reversible adhesion. The nanotip SMP surface, characterized by an RMS roughness (R_q) exceeding 100nm, mitigates surface adhesion to zero through its rough topography. In its rubbery state, this surface allows for conformal contact with the object by reducing roughness, while transitioning to a glassy state results in increased adhesion due to shape-locking effect. Then, to release the object, the SMP surface is reverted to its original nanotip surface through the shape memory effect, inducing a return to a rough state and enabling easy release.<br/>This mechanism underscores the achievement of great adhesion reversibility across varying scales, marking the capability of programmable and precise large-scale transfer printing at the 5μm level chips. The applications of this approach, such as micro LED transfer and repair are showcased, suggesting its potential as a next-generation display solution with enhanced yield and precision.