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.