Figure 1. Schematics of the PiP process, and replication mechanism.

(a) Each imprint was made by layering an untreated, unpatterned (blue) film on top of a crystallized, patterned silk fibroin master (yellow). These samples were placed on a heated substrate at 120°C for 60 seconds, with ~50 Psi pressure. Reflow of the untreated films, to generate an inverse pattern in the untreated film (SEM micrographs, inset) complete the pattern transfer. Duplication can be carried out by using each generation to imprint the next, as shown with red representing patterns on the blue films, making the technique truly high-throughput. (b) Lap shear bond strength for two overlapped, PiP- pressed films of untreated and 120°C 60 seconds pretreatment. A 6-fold decrease in bond strength was seen with the crystallized films. (c) Crystallization rates (red points) as measured through quantified FTIR (see methods), and residual water content (blue points), as quantified through TGA, for films throughout the PiP process. A crystallized plateau was reached after 15 seconds of pressing. Water loss follows the inverse pattern of crystallization, rapidly decreasing from ~10.5% to ~7.25% with treatment.