Inkjet printing of individual polymer micro parts self-shaped with hemispherical caps

Droplet deposition has been so ubiquitous over a decade for the production of micro parts using versatile liquid-based methods such as inkjet-printing technology. One of key elements for success in the design involves the use of non-homogeneous substrates to effectively control the complex morphologies of solute deposit during evaporation. However, there are still few studies investigating contours of the solid contents self-formed and even released as the solvents evaporate. This paper reports a droplet vaporization deposition (DVD) method that can significantly improve the controllability over the curvatures of micro parts utilizing the heterogeneous PDMS (Polydimethysiloxane) substrates based on soft-lithography technique. Experimental and analytical results indicate that the profile curvatures and contact angles (up to ∼90°) for the hemispherical parts formed after droplet evaporation were simply varied by different droplet volumes (single droplet ∼10 pl) placed on the cavity-structured surfaces, thus providing the capability of control over solid contours. In this way, the individual micro parts released from the mold substrates could be applied in many applications, in particular the current self-assembly processes.