Polycarbonate Nanotopographical Surfaces

Polycarbonate nanotopographical culture surfaces comprised of 120 nm diameter pits were produced by injection molding using an Engle Victory 28 hydraulic injection moulder. Master SQ (300 nm centre-centre spacing and 100 nm depth arrays) or NSQ (arrays with an additional 50 nm offset spacing of pits) nickel dies were produced from patterned resists of silicon-coated substrates fabricated on silicon-coated 100 nm PMMA (Elvacite 2041, Lucite International) by electron beam lithography. The silicon substrates were exposed to a 50 kV electron beam, developed in 1:3 MIBK:IPA for 30 s, rinsed in IPA and dried in a nitrogen stream. Patterned resists were sputtered coated ith 50 nm Ni-V and electroplated to a thickness of ~300 μm (outsourced to DVDNorden, Denmark). Nickel shims were chloroform cleaned for 10–15 min in an ultrasonic bath, rinsed in acetone and IPA, and dried once more in gaseous nitrogen. Surfaces were produced by injection moulding through heating polycarbonate (Makrolon® OD2015) to 180 °C and applying a clamping force of 250 kN to imprint nanotopographical pattern onto the surface of the polycarbonate. Final dimensions of each substrate being 24 mm × 24 mm. After cooling to 70 °C, separation of the press and polymer surfaces was achieved. Unpatterned (flat) polycarbonate substrates were injection moulded against planar shims and used as controls.