title: Droplet-driven transports on superhydrophobic-patterned surface microfluidics.
abstract: Droplet-based transport phenomena driven by surface tension have been explored as an automated pumping source for a number of chemical and biological applications. In this paper, we present a comprehensive theoretical and experimental investigation of unconventional droplet-based motions on a superhydrophobic-patterned surface microfluidic (S(2)M) platform. The S(2)M surfaces are monolithically fabricated using a facile two-step laser micromachining technique on regular polydimethylsiloxane (PDMS) chemistry. Unlike the traditional droplet-driven pumps built on an enclosed microfluidic network, the S(2)M network pins the liquid-solid interface of droplets to the lithographically defined wetting boundary and establishes a direct linkage between the volumetric and hydraulic measures. Moreover, diverse modes of droplet motions are theoretically determined and experimentally characterized in a bi-droplet configuration, among which several unconventional droplet-driven transport phenomena are first demonstrated. These include big-to-small droplet merging, droplet balancing, as well as bidirectional transporting, in addition to the classic small-to-big droplet transition. Furthermore, multi-stage programmable bidirectional pumping has been implemented on the S(2)M platform, according to the newly established droplet manipulation principle, to illustrate its potential use for automated biomicrofluidic and point-of-care diagnostic applications.
authors.affiliation: Micro-Nano Innovations (MiNI) Laboratory, Department of Biomedical Engineering, University of California, Davis, USA.
authors.forename: Siyuan
authors.initials: S
authors.lastname: Xing
authors.forename: Ryan S
authors.initials: RS
authors.lastname: Harake
authors.forename: Tingrui
authors.initials: T
authors.lastname: Pan
mesh_terms: D004129:Dimethylpolysiloxanes / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D044085:Microfluidics; D008962:Models, Theoretical; D013499:Surface Properties
chemical_list: D004129:Dimethylpolysiloxanes; C013830:baysilon