# Tulip-Shaped Pattern Imprinting for Omni-Phobic Surfaces Using Partially Cured Photopolymer
## 2 Process Design and Experiments
### Comparison of Micro-Pattern Morphology Before and After Experiments  
To fabricate omni-phobic surfaces, experiments were performed by designing a process wherein hydrophobicity and oleophobicity would be achieved by increasing the deformation and roughness of the surface patterning via a follow-up treatment of the curing-inhibited PUA resin. As the main variable for the experiment, the UV irradiation energy was chosen. Figure 3 shows the scanning electron microscopy (SEM) images to analyze the pattern morphology change before and after the experiments. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **Base (wt \%)** & **Curing Agent (wt \%)** & **Softening Agent (wt \%)** \\ \hline \#A & 76.1 & 10.9 & 13 \\ \#B & 78.3 & 8.7 & 13 \\ \#C & 79.7 & 7.3 & 13 \\ \#D & 75 & 8.3 & 16.7 \\ \#E & 72 & 8 & 20 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Combination ratios of PDMS samples. Figure 2: Oxygen transmission rate according to combination ratio of polydimethylsiloxane (PDMS). Observing the deformed pillar pattern, the diameter of the lower part of the pattern shown in Figure 3c was increased from the minimum of 6.35 \(\upmu\)m to the maximum of 8.20 \(\upmu\)m by irradiation with 150 mJ UV energy, as shown in the conceptual diagram. The diameter before the deformation was 10 \(\upmu\)m; this was reduced by 1.8-3.65 \(\upmu\)m. The diameter of the upper part was increased from 11.1 \(\upmu\)m to 12.6 \(\upmu\)m, indicating an increase reaching 2.6 \(\upmu\)m. In addition, the height of the pillar was measured as 15.7 \(\upmu\)m to 17.1 \(\upmu\)m, reduced by 2.9-4.3 \(\upmu\)m from the original height of 20 \(\upmu\)m. Furthermore, irregularities of 480 nm-2.4 \(\upmu\)m in height were generated on the upper surfaces of the pillars, thus changing the nano- and micro-scale roughness. Contact angle measurements were performed using Smart Drop equipment (FEMTOBIDMED Inc., Seongnam-si, Korea) to verify hydrophobicity, with results as shown in Figure 4. The volume of fluid in contact angle testing was set to 10 \(\upmu\)L. The measurement was repeated at five random points on the patterned region of the film. An excellent contact angle corresponding to hydrophobicity of at least 155.9\({}^{\circ}\) and a maximum of 166.0\({}^{\circ}\) was confirmed. For the pattern irradiated with 180 mJ UV energy (Figure 3d), there was a reduction of 0.74-1.53 \(\upmu\)m in the diameter of the lower part, from the minimum of 8.47 \(\upmu\)m to the maximum of 9.26 \(\upmu\)m. The diameter of the upper part was increased by up to 1.2 \(\upmu\)m from 10.4 \(\upmu\)m to 11.2 \(\upmu\)m, and the height was decreased by up to 1.3 \(\upmu\)m from 17.2 \(\upmu\)m  
Figure 4: Contact angle measurement results of imprint film according to UV irradiation energies. Figure 3: Micro-pattern deformation before and after tulip-shaped pattern imprinting process (variable: ultraviolet (UV) energy). (**a,b**) Hexagonal pillar array pattern morphology before experiments. (**c–e**) Hexagonal pillar array pattern morphology after experiments; UV irradiation energy: (**c**) 150 mJ, (**d**) 180 mJ, (**e**) 300 mJ. (**f,g**) Hexagonal wall-pillar array pattern morphology before experiments. (**h–j**) Hexagonal wall-pillar array pattern morphology after experiments; UV irradiation energy: (**h**) 150 mJ, (**i**) 180 mJ, (**j**) 300 mJ. to 18.7 \(\upmu\)m. The maximum height of irregularities occurring on the upper surface of the pattern was 824 nm. The contact angle measured using the corresponding imprint sample was 150.6\({}^{\circ}\)-166.3\({}^{\circ}\), confirming hydrophobicity. For the pattern deformed by irradiation with 300 mJ UV energy (Figure 3e), the diameters of the top and bottom were measured as 9.79-9.92 \(\upmu\)m and 9.66-9.79 \(\upmu\)m, respectively, while the height increased from 18.6 \(\upmu\)m to 20.1 \(\upmu\)m. The measured diameter below the design dimension of 10 \(\upmu\)m was considered an experimental error that occurred during imprinting.