AVS 51st International Symposium
    Biomaterial Interfaces Friday Sessions
       Session BI+MN-FrM

Paper BI+MN-FrM11
Measurement and Analysis of Changes in EOF with Protein Adsorption using the Dynamic Current Monitoring Method.

Friday, November 19, 2004, 11:40 am, Room 210D

Session: Bio-MEMS and Microfluidics
Presenter: K. Lenghaus, Clemson University
Authors: K. Lenghaus, Clemson University
M.J. Tarlov, NIST
L. Locascio, NIST
J. Jenkins, CFD Research Corporation
S. Sundaram, CFD Research Corporation
S. Krishnamoorthy, CFD Research Corporation
J.J. Hickman, Clemson University
Correspondent: Click to Email
The high surface to area ratio of MEMS devices places certain constraints upon their operation. One of these is that conventional, pressure driven flow is a relatively inefficient means of moving liquids through microfluidic channels, owing to the large backpressure encountered. The parabolic flow profile of pressure driven flow can also be undesirable in certain applications, especially in regards to sample separation and delivering analytes to detectors. Electro-osmotic flow (EOF), providing that conditions are conducive to its operation, can thus be a preferable option, since it doesnâ?Tt have the same problems with high backpressures, and its top hat flow profile, as shown by capillary electrophoresis, is well suited to separations and analysis. However EOF is sensitive to the type and density of electrical charges at the wall, and the adsorption of molecules or biomolecular species can substantially alter the EOF characteristics of the system. Using the dynamic current monitoring method, the change in EOF with protein exposure was tracked on the timescale of minutes, and the effect of changing the driving voltage, buffer composition, capillary surface and other parameters was obtained. Building on our previous protein adsorption work, we show that under some circumstances changes in EOF with exposure to different proteins can be extremely rapid. Whether or not desorption and recovery of the original EOF characteristics occurs depends on the specific protein/surface combination, as does the final EOF reached. The rates of adsorption and desorption were also determined using finite element analysis methods, compared with those obtained under pressure driven flow conditions, and a hypothesis of the method of interaction has been postulated.