Optical microscopy images of the patterned P3HT layers using the PDMS mold with the pillar array of 100 μm diameter. (a–e) The negatively patterned P3HT layers using chloroform as a solvent. The PDMS molds were used as templates for dewetting of the polymer solutions, accompanying with solvent evaporation. The solution concentrations were (a) 3.00, (b) 2.00, (c) 1.00, (d) 0.50, and (e) 0.25 wt%, respectively. (f–j) The negatively patterned P3HT layers, prepared with chlorobenzene as a solvent following the same procedure as for chloroform. The solution concentrations were (f) 2.00, (g) 1.00, (h) 0.50, (i) 0.25, and (j) 0.10 wt%, respectively. (k–o) The positively patterned P3HT layers via direct contact printing. The chloroform solvent was solely used for spin-coating deposition of the polymer on the PDMS surface due to serious dewetting issues. The solution concentrations were (k) 3.00, (l) 2.00, (m) 1.00, (n) 0.50, and (o) 0.25 wt%, respectively.