Rate-Dependent Adhesion Between a Spherical PDMS Stamp and Silicon Substrate for a Transfer-Assembly Process

The transfer-assembly process is a promising technique for fabricating high-performance flexible devices. An important element of the transfer assembly process is controlling the adhesion during the picking and placing steps. In this study, we developed an apparatus to measure the adhesive force between a spherical polydimethylsiloxane (PDMS) stamp and a flat silicon substrate. The apparatus consisted of a multi-axis stage for alignment, a vertical stage, and a loadcell. The adhesive force between the stamp and the substrate was measured for various unloading velocities during the picking step. The size of the contact area was simultaneously measured during the picking step by incorporating an optical microscope with a high-speed camera into the apparatus. The effect of the unloading velocity on the adhesion was carefully investigated. The actual transfer process was performed to demonstrate the effect of rate-dependent adhesion during the transfer assembly of single-crystal silicon devices. Practical gui...