Hemorheology in microchannels
We often consider the flexible, biconcave human erythrocyte (red blood cell) as "perfectly" suited for the variety of flow conditions it will encounter in vivo, from Reynolds number of ~2000 near the heart to contorting through capillaries nearly half the cell's diameter. However, current fluid dynamics literature largely ignores both the significant variation in erythrocyte size across mammalian species (~4-12 microns) as well the shape variation seen in oviparous vertebrates. In addition, within channel diameters of 10-300 microns, blood exhibits unique behaviors via the Fahraeus and Fahraeus-Lindqvist effects. We seek to understand the role of erythrocyte size and shape within the context of these effects with the goal of better control and manipulation of blood flow in microfluidic devices.
Point-of-care system for quantitative measurements of blood analytes using graphene-based sensors
Serum gluocse, cholesterol, triglyceride and HbA1C monitoring are all valuable tools in the health management of the aging population, especially given the current rise in diabetes and cardiovascular diseases. Even for glucose monitoring, the challenges in obtaining sufficiently accurate and reliable measurements are so significant that the FDA is contemplating more stringent standards. Guide Freckmann et al., J Diabetes Sci Tech 2012 6:1060-75 have compared 43 blood glucose self-monitoring systems. 34 of these systems were completely assessed, and 27 (79.4%) of these 34 fulfill the minimal accuracy requirements while only 18 (52.9%) fulfill the proposed tighter criteria in the current drafted standards. None of them meet the even more stringent requirements of ISO 2012. Because inaccurate systems bear the risk of false therapeutic decisions and rising health care costs, there is an urgent need for significantly enhanced blood glucose monitoring systems for point-of-care applications. Point-of-care tests for other biomedically important analytes are generally even less accurate. The overall goal of the proposed research is to develop new sensor platforms that will provide increased sensitivity and accuracy in point-of-care situations. This is a joint project with Harvard Medical School and Vanderbilt University.
Hot embossing techniques for BioMEMs
PDMS is the predominant material-of-choice for BioMEMs research. However, its permeability and lack of durability make it impractical for most real-world applications. We are interested in the use of hot embossing to take advantage of alternate materials and integration of electrical components. This research complements the other ongoing bioMEMs projects in the lab.
Surface topology optimization for directing fluid flow
Sample capture transport of biological fluids, like blood flow in diabetes glucose monitors, often requires microfluidic actuation. Current commercial methods used in diabetes glucose monitors usually involve porous materials or hydrogels, but these strategies are limited in fluid control. Surface wettability gradient actuation is an approach widely used in various other microfluidic or lab-on-a-chip systems. Here we design and fabricate a droplet-actuation device that relies purely on capillary pressure gradients induced by surface topologies. We discuss the theoretical capabilities of directing such fluid flows using no thermal gradients or external power sources. Current work focuses on pillar capillary designs on a polydimethylsiloxane (PDMS) substrate and water droplets (0.25 ~ 5 Î¼L) in low Bond number. The work is extending to more complex biological fluids including blood.