Synthesis of large area crack-free nanostructured TiO2 with selective masking for cell/electronics interfacing

The biocompatibility of Nanostructrued TiO₂(NST) makes it a promising material in biological applications. Recently reported aqueous oxidation technology synthesizes NST at very low temperature, which is CMOS compatible. It suggests NST a very promising candidate for cell/electronics interfacing. However, severe cracks have been observed beyond a threshold dimension (20μm × 20μm). In this study, the residue stress of NST was measured using the local curvature method. It is revealed that extra oxidation time or higher oxidation temperature would induce large residual stress, and the mask boundary played an important role. Crack-free NST with SU-8 soft mask has been fabricated in hydrogen peroxide(H₂O₂) solution at 80°C. The NST film features a large dimension above 750 × 750μm with a thickness of O.6μm. With a low contact angle, the patterned NST promoted fibroblast cell adhesion, compared to Ti and thermal SiO₂.