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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 (S2M) platform. The S2M 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 S2M 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 S2M platform, according to the newly established droplet manipulation principle, to illustrate its potential use for automated biomicrofluidic and point-of-care diagnostic applications. [ABSTRACT FROM AUTHOR]

In this paper, a nanocomposite approach is introduced to provide both electrically conductive and optically transparent micropatterns on any flexible substrate employing photolithography-based microfabrication. The nanocomposite materials combine the highly directional nanoscopic networks and electrical conductivity of single-wall carbon nanotubes (SWNTs) with the photopatternability and optical transparency of SU-8 photoresist. The photopatternable nanocomposites have yielded high optical transparency of 90% and high electrical conductivity of 27.5 S m[?]1 with the minimal feature resolution of 10 um. Additionally, an interesting nano-bridge phenomenon has been discovered during fabrication of the microscale features. Moreover, the photopatternable transparent conductive nanocomposite has demonstrated its application to biomedical sensing for exceptional adaptability and flexibility. [ABSTRACT FROM AUTHOR]