4.2.1. Preparation of perfluoropolyether (PFPE) mold
The PFPE resin (Fluorolink MD700, Solvay Solexis, Milan, Italy) was mixed with 3% w/w photoinitiator (Darocur 1173, Sigma Aldrich, St. Louis, MO, USA) to create the UV-curable resin. Then, the patterned silicon substrate (e.g., Si master) was coated with the UV-curable resin and covered with polyethylene terephthalate (PET) film as a backplane. The PET film was then rolled over to the UV-curable resin to distribute it evenly and the mixture was cross-linked by exposure to UV light at 365 nm for 5 minutes. After the curing process, the PFPE mold was detached from the Si master.