Fabrication of metallic microstructure on curved substrate by optical soft lithography and copper electroplating

Microfabrication of copper structures with a high aspect ratio was successfully performed on a curved substrate by optical soft lithography and metal electroplating. This fabrication method comprises mainly of three steps. Firstly, a flexible polymer photomask was fabricated by a direct metal transfer technique via two types of self-assembled monolayer treatments. Next, SU-8 micro patterns were fabricated on a curved glass substrate by optical soft lithography. Here, we utilised a mask with a microslit and a flexible polymer photomask. Lastly, copper electroplating was performed on the curved substrate using the SU-8 patterns as molds to form high-aspect-ratio copper structures. We confirmed that SU-8 microline patterns with an aspect ratio of over 2.5 were formed on the curved substrate. Subsequently, copper structures fabricated on the curved substrate with SU-8 micro patterns were acquired. The unconventional microfabrication technique introduced in this work can be used for the fabrication of 3-D high-aspect-ratio metallic microstructures on curved or nonplanar substrates.