Selective Micro-Transfer Printing of Microspheres Using Adhesion-Switchable Stamp

This article introduces a selective micro-transfer printing technique for microsphere assembly based on the thermo-responsive adhesion modulation of a shape memory polymer (SMP) stamp. The method offers a solution to the challenges encountered when transferring materials or devices at the microscale, particularly those with uneven surface topography. By selectively modulating the surface adhesion of the SMP stamp with micro-heaters, this method demonstrates precise and selective transfer of 100 μm micro solder balls and 50 μm Polystyrene (PS) microspheres, where the pitch is 200 μm for the array. Analysis of the positions before and after transfer indicates the maximum registration error is less than 2 μm. The selectivity and reliability of this micro-transfer printing process for microspheres suggest potential applications of the method in micro-assembly and advanced packaging.