A pH-UV Dual-Responsive Photoresist for Nanoimprint Lithography That Improves Mold Release

We have developed a degradable photoresist that is responsive to pH and ultraviolet light (UV). This dual-responsive resist consists of 5,7-diacryloyloxy-4-methylcoumarin (fluorescent monomer), acrylic anhydride, and 3,6-dioxa-1,8-dithiooctane. It can be photocured using thiol–acrylate polymerization and photodimerization of coumarin moieties under 365 nm UV light exposure. The cured resist is degradable in aqueous solutions with pH > 7. The degradation process can be characterized by the change of fluorescence intensity in the aqueous solution. In this study, we have analyzed the properties of the degradation of the resist by changing the pH of the solution and its exposure time under 254 nm UV light. This UV exposure can induce photocleavage of the coumarin dimers. We then used these materials to fabricate micropatterns through nanoimprint lithography (NIL) process. Compared with other conventional degradable materials capable of NIL, the dual-responsive resist can help to clean the NIL mold easily at room temperature. This resist is also more environmentally friendly, is relatively low cost, can be faster to degrade, and is easier to characterize. It also has low volume shrinkage, which may have a valuable and positive effect on the development of NIL.