Switchable Adhesive Based on Shape Memory Polymer with Micropillars of Different Heights for Laser-Driven Noncontact Transfer Printing.

Switchable adhesive is essential to develop transfer printing, which is an advanced heterogeneous material integration technique for developing electronic systems. Designing a switchable adhesive with strong adhesion strength that can also be easily eliminated to enable noncontact transfer printing still remains a challenge. Here, we report a simple yet robust design of switchable adhesive based on a thermally responsive shape memory polymer with micropillars of different heights. The adhesive takes advantage of the shape-fixing property of shape memory polymer to provide strong adhesion for a reliable pick-up and the various levels of shape recovery of micropillars under laser heating to eliminate the adhesion for robust printing in a noncontact way. Systematic experimental and numerical studies reveal the adhesion switch mechanism and provide insights into the design of switchable adhesives. This switchable adhesive design provides a good solution to develop laser-driven noncontact transfer printing with the capability of eliminating the influence of receivers on the performance of transfer printing. Demonstrations of transfer printing of silicon wafers, microscale Si platelets, and micro light emitting diode (μ-LED) chips onto various challenging nonadhesive receivers (e.g., sandpaper, stainless steel bead, leaf, or glass) to form desired two-dimensional or three-dimensional layouts illustrate its great potential in deterministic assembly.