Inherent Constraint for Three-Dimensional Patterning by Microtransfer Molding

As one of the reversal imprint processes, microtransfer molding (TM) is considered a promising process to fabricate three-dimensional (3D) microstructures. However, two critical challenges, ink full filling and ink complete transfer, limit its 3D patterning ability. In this paper, the critical contact angle of ink on imprint mold ((C_ink-mould)) and that on substrate ((C_ink-substrate)), are defined to indicate the critical conditions for ink full filling and complete transfer, respectively. A model is developed to indicate the inherent competition between the interface energies of ink on imprint mold and substrate to meet ink full filling and complete transfer. A feasible region forTM process, which can satisfy ink full filling and complete transfer simultaneously, is proposed, and it reveals the inherent constraint between ink full filling and complete transfer. Experiments show that the feasible region forTM process can predict whether the 3D patterning can be achieved for the given ink/mold/substrate match; thus it provides a criterion to select matched materials or proper surface-treatments to achieve high fidelity 3D patterning byTM process.