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Glaucoma, one of the leading causes of irreversible blindness, is a progressive neurodegenerative disease. Chronic elevated intraocular pressure (IOP), a prime risk factor for glaucoma, can be treated by aqueous shunts, implantable devices, which reduce IOP in glaucoma patients by providing alternative aqueous outflow pathways. Although initially effective at delaying glaucoma progression, contemporary aqueous shunts often lead to numerous complications and only 50% of implanted devices remain functional after 5 years. In this work, we introduce a novel micro-device which provides an innovative platform for IOP reduction in glaucoma patients. The device design features an array of parallel micro-channels to provide precision aqueous outflow resistance control. Additionally, the device's microfluidic channels are composed of a unique combination of polyethylene glycol materials in order to provide enhanced biocompatibility and resistance to problematic channel clogging from biofouling of aqueous proteins. The microfabrication process employed to produce the devices results in additional advantages such as enhanced device uniformity and increased manufacturing throughput. Surface characterization experimental results show the device's surfaces exhibit significantly less non-specific protein adsorption compared to traditional implant materials. Results of in vitro flow experiments verify the device's ability to provide aqueous resistance control, continuous long-term stability through 10-day protein flow testing, and safety from risk of infection due to bacterial ingression.

A rotational stage with a 10-mm-diameter single-crystal silicon rotor supported by liquid droplet ball bearings is described. The 100-300-μm-thickness droplet bearings are retained on the rotor surface with a micropatterned amorphous-flouropolymer-based superhydrophobic (SHP) surface coating that yields a 156° contact angle. The droplets slide on a SHP bearing raceway that is formed from laser-roughened poly-dimethylsiloxane (PDMS) on the surface of the stator, achieving a 10°-contact-angle hysteresis that results in very low sliding friction. The stage is driven by a rotating external magnetic held that provides up to 3 μN · m torque through a permanent magnet mounted on the rotor. The liquid bearing provides a passive wear-free interface between rotor and stator with a measured drag coefficient of 0.94 · 10-3 μN · m/r/min, rotating up to a speed of 2400 r/min, and a mean minimum operating torque of 0.3 μN · m. The bearing design is stable in position and tip/tilt, with a tip mode stiffness of 5.4 μN · m/deg and measured nonrespectable rotor wobble of 0.3 mrad. The experimentally measured bearing stiffness, drag coefficient, and startup torque are shown to compare well with values predicted from analytical models based on surface tension forces on the droplet bearings.

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.