Thermal Controlled Tunable Adhesive for Deterministic Assembly by Transfer Printing

Transfer printing techniques based on tunable adhesives that enable heterogeneous integration of materials in desired layouts are essential for developing existing and envisioned systems such as flexible electronics and micro-LED (µ-LED) displays. Here, a novel thermal controlled tunable adhesive, which not only has the ability of eliminating the interfacial adhesion for printing but also provides a new strategy for enhancing the interfacial adhesion for pick-up is reported. The tunable adhesive features cavities filled with air on the surface. This simple construct offers thermal controlled suction and thrust with their amplitudes on the order of a few tens of kPa within 100 °C temperature change, which enables a reliable damage-free transfer printing. Systematically theoretical and experimental studies reveal the underlying thermal induced pressure change mechanism and provide insights into the design and operation of the thermal controlled tunable adhesive. Demonstrations of this smart adhesive in manipulation of various surfaces and transfer printing of micro-scale Si inks and µ-LEDs illustrate its unusual capabilities for deterministic assembly by transfer printing. © 2021 Wiley-VCH GmbH.