Indirect Additive Manufacturing of Hydrophobic Reentrant Surface Structures using Fused Deposition Modelling

Abstract

Hydrophobicity is an important feature in medical applications. Reentrant structures are used to achieve this functionality on the surface to the greatest extent possible. This study provides a simple and cost-effective approach to producing these structures without the use of nanoparticles and fluorine-based coatings that can make this approach applicable to medical devices. This was done by indirect 3D printing using a low-cost commercially available Fused Deposition Modelling (FDM) printer. The FDM printer is used to create a mold with a top layer of straight lines separated by a gap. Polydimethylsiloxane (PDMS) is cast into it negatively replicating the mold surface to make the reentrant structures. As a result, a functionalized surface with the reentrant wall structure having an edge angle of 121° ± 10° was created with anisotropic wetting reaching an optimal static contact angle of 160.3° ± 2.9° with the lowest rolling angle of 29.2° ± 4.2° for a 10 uL water droplet.