## 2 Experimental Procedure
### Nanoimprint Resist Material Containing a UV Reactive Fluorine Surfactant  
The properties of nanoimprint resist material include low viscosity, low vapor pressure, high sensitivity in UV irradiation, minimal film volumetric shrinkage during UV curing process, suitable mechanical strength, and suitable thermal stability. The low viscosity of the nanoimprint resist material is necessary to enable the dispense technique and the low pressure capillary fill process in UV curing nanoimprint lithography. The low vapor pressure of the nanoimprint resist material allows a smaller droplet size to be used in the dispense process, which increases the drop pattern resolution and volume  
Figure 2: Schematic of process cycles in UV curing nanoimprint lithography: (**1**) deposition of resist droplets; (**2**) spreading of resist by nanoimprinting; (**3**) UV irradiation; and (**4**) template release.  
control, and improves the overall process throughput. The high sensitivity to UV irradiation was related to a fast UV curing rate, which enables an ambient temperature imprint process and improves the overall throughput in mass fabrication. The low film volumetric shrinkage of the nanoimprint resist material in the UV curing reaction is necessary to maintain both patterning dimensional accuracy and lithographic resolution in UV curing nanoimprint lithography, in order to prevent pattern distortions and crack formations during the UV curing reactions. The nanoimprint resist material needs to have suitable mechanical strength and thermal stability, to survive the environmental stress during the nanoimprint and etch processes.  
The chemical structures of the developed nanoimprint resist material containing a UV reactive fluorine surfactant are shown in Figure 3. Heptadecafluoro-2-hydroxyundecyl acrylate as a UV reactive fluorine surfactant was blended with tricylodecane dimethanol diacrylate as a bulk polymerizable organic monomer, dipentaerythnitol polyacrylate-based composition as a UV crosslinker, and 2-hydroxy-2-methyl-1-phenylpropane-1-one as a photoinitiator. The bulk polymerizable organic monomers had low viscosity and can be rapidly polymerized. The UV crosslinker had the suitable mechanical strength and the thermal stability of the polymerized nanoimprint resist. The liquid photoinitiator needed to have a UV curing reaction. The nanoimprint resist materials are often formulated from the above process requirements with additional modifications tailored for the specific application. Table 1 shows the formulation of the prepared nanoimprint resist materials at three different weight ratios of heptadecafluoro-2-hydroxyundecyl acrylate; 9.0 wt% (sample name: TPULR9), 4.5 wt% (TPULR4.5), and 0 wt% (TPULR0). The resulting nanoimprint resist materials were filtered through an ultrahigh-molecular-weight polyethylene membrane filter having an average pore size of 50 nm.  
Figure 3: Chemical structures of the nanoimprint resist material containing a UV reactive fluorine surfactant: (**a**) heptadecafluoro-2-hydroxyundecyl acrylate; (**b**) tricylodecane dimethanol diacrylate; (**c**) dipentaerythnitol polyacrylate-based composition; and (**d**) 2-hydroxy-2-methyl-1-phenylpropane-1-one.  
The spin-on underlayer material with terminal methacrylate groups was developed to improve the dirty-template-causing resist pattern peeling and defect on the template due to stronger adhesion between the resist material and the underlayer, compared with that between the template and resist material [3]. The underlayer was then named as TPU-UL.