Contact printing stamp preparation. Polydimethylsiloxane was prepared using a 10:1 weight ratio of base resin to curing agent. This mixture was stirred for 10 min and subsequently desiccated for 20 min. The uncured mixture was then poured onto a micro-patterned silicon wafer to a thickness of 1 cm. The polydimethylsiloxane was then heat cured at 145 °C over 15 mins, mediating pattern transfer from the wafer to the polymer. The cured polymer was then cut into 1 cm ´ 1 cm ´ 1 cm cubes, which were used as stamps for microcontact printing.