Wettability and Capillary Flow in Vat-Printed Microfluidic Channels

Vat photopolymerisation enables monolithic microchannels but also creates process-dependent surfaces whose wetting behaviour can influence filling, droplet motion and two-phase flow. Direct DLP evidence shows that layer thickness and lamination direction can change surface roughness, contact angle, contact-angle hysteresis and capillary movement [1]. A separate SLA study found time-dependent contact-angle change in a printed polymer and linked that evolution to the practical window for self-driven capillary microfluidics [2]. Surface modification can deliberately change channel wetting, as demonstrated in DLP-printed devices for two-phase flow [3], while printed microtexture can alter apparent contact angle even when bulk chemistry is unchanged [4]. ER-97 therefore distinguishes static contact angle, advancing/receding behaviour, surface free energy, roughness, capillary pressure and actual flow. It also separates final-part wall wettability from resin-vat/release-film wetting during printing, an important boundary in microchannel overcure studies [5]. The qualification architecture requires final-state conditioning, defined probe liquids, multiple locations/orientations, roughness or topography where relevant, ageing checks after surface treatment, and direct channel-flow validation under the intended fluid and geometry.