Preparation of hybrid soda-lime/quartz glass chips with wettability-patterned channels for manipulation of flow profiles in droplet-based analytical systems

Profile switching of two-phase flows is often required in microfluidic systems. Manipulation of flow profiles can be realized by control of local surface energy of micro channel through wettability-patterning of channel surface. This article presents a facile approach for wettability-patterning of the micro channels of glass chips. Commercially available octadecyltrichlorosilane (OTS) was used to hydrophobilize the channels via the formation of OTS self-assembly monolayer (SAM), and a UV-source that mainly emits deep UV-light of 254 and 185 nm was employed to degrade the in-channel formed OTS-SAM. The architecture of soda-lime glass/quartz glass hybrid chip was designed to facilitate the deep UV-light effective degrading the OTS-SAM. The established approach, together with the side-by-side laminar-flow patterning technique, was applied to prepare various finely patterned channel networks for different tasks of flow profile switching. The micro device capable of conducting the profile switch from W/O droplets to two separated continuous phases was demonstrated to perform on-chip quick liquid–liquid extraction for the determination of partition coefficients of pharmaceuticals.

Smooth flow profile switching of two-phase flows can be realized in the wettability-patterned channels. (a) From the W/O droplet flow to O/W droplet flow; (b) from W/O droplet flow to side-by-side laminar flow; and (c) from O/W droplet flow to side-by-side laminar flow. The two immiscible fluids were n-octanol (transparent) and aqueous dye solution (blue-colored).Figure optionsDownload as PowerPoint slideHighlights
► Channels were wettability-patterned via UV-lithography of OTS coated in channel.
► Hybrid soda-lime/quartz glass chip facilitated UV degrading in-channel-coated OTS.
► Smooth profile switch of two-phase flows was realized in the patterned channels.
► Partition coefficients of drugs were determined via on-chip solvent extraction.