Design and direct additive manufacturing of three-dimensional surface micro-structures using material jetting technologies

The ability to directly print 3D microstructures across the surface of large dimension substrates opens up numerous possibilities not feasible with conventional 2D or 2.5D printing or coating techniques. Demonstrated herein is a method to print 3D microstructures onto clear poly(methyl methacrylate) (PMMA) plates using material jetting technologies. Contact angle and profilometry analysis indicated that the VeroCyan TM photopolymer had enhanced wetting of the PMMA surface leading to greater droplet spreading affecting the geometries printed compared to VeroCyan TM integrated models. Strategies to manipulate the interfacial interactions and hence adhesion of the VeroCyan TM photopolymer were investigated by varying PMMA surface free energy through physio-chemical and chemical techniques including (i) corona discharge, followed by post-treatments with 3-(trimethoxysilyl)propyl methacrylate, polyethyleneimine graft chemicals, and (ii) plasma treatments with air and plasma polymerisation of 1,7-octadiene. The surface chemistry and wetting behaviour played a crucial role in influencing interfacial interactions with the VeroCyan TM photopolymer hence its adhesion to the PMMA surface.