A Sharp Phase Transition Shape Memory Polymer for Micro-transfer Printing

Micro-transfer printing (μTP) technology facilitates the transfer of microstructures and microdevices from an original substrate to a target substrate. In this process, the adhesion dynamics of the transfer tool play a critical role. Shape memory polymers (SMPs) offer a significant advantage in this application, attributed to their adjustable adhesion force, which can be modulated through external stimuli such as temperature. Our study introduces a thermo-responsive SMP with a distinct sharp phase transition (SPT) characteristic, primarily composed of stearyl acrylate (SA) and urethane diacrylate (UDA). This material exhibits a rapid transition between rubbery and rigid states upon temperature changes, significantly altering the adhesion force crucial for the μTP process. The SPT SMP exhibits a 12× improvement in adhesion strength ratio, approximately 189:1 between pick-up and release phases, compared to a PDMS stamp, enhancing the reliability and expanding the potential uses of μTP technology. Additionally, the SPT SMP’s rapid transition between rubbery and rigid states facilitates spatial selectivity in μTP. This characteristic enables densely packed device configurations on the original substrate, improving wafer utilization, while in the meantime enabling selective transfer of devices without affecting adjacent devices.