Polydimethylsiloxane (PDMS, DC184, Dow Corning, Elizabethtown, KY, USA) and a glass piece (20 mm × 20 mm × 0.13 mm) were used for the fabrication. First, the silicone elastomer and the curing agent were mixed in a 10:1 proportion (22 g in total). The mixture was then poured into...