Fabrication and characterization of a polydimethylsiloxane microfluidic pump for direct-sampling neuroscience experiments, with in-line capillary electrophoresis - laser-induced fluorescence chemical analysis

Abstract

A polydimethylsiloxane (PDMS) peristaltic micropump was designed, fabricated, and characterized, for intended use within rodent brain direct-sampling neuroscience experiments, with capillary electrophoresis - laser-induced fluorescence (CE-LIF) chemical analysis. The micropump was fabricated in-part using replica molding (REM) and injection molding. The micropump channel was formed by bonding an open PDMS Gaussianshaped micromolded channel, to a featureless slab of PDMS. Two pieces of capillary tube interconnects were sealed within the closed-off microchannel, and used to make connections with the outside world. The micropump was actuated using piezoelectric cantilevers, with a precision machined microvalve attached to the tip of each cantilever actuator. Registration of the cantilevers and microvalves over the PDMS microchannel, was accomplished with the aid of in-house machined micropositioners. The micropump was thoroughly characterized, for use and application as a bio-analytical add-on attachment device, to an already existing CE-LIF instrument. The micropump was characterized for: various microchannel geometries; different microvalve sizes, tilt, positioning, and shutoff performance; micropositioner design and performance; and, flow rate, backpressure, and peristaltic signal analysis. A P-Q (or H-Q) plot was formed, to represent the performance of the micropump for maximum attainable backpressure (P), versus flow rate (Q). The linear plot was formed by experimentally collecting fourteen individual data points, each corresponding to a unique micropump, “state.” The P-Q plot as discussed within Chapter VIII, is very potent, in providing a 5-for-1 benefit ratio. The P-Q plot allows an experimentalist to obtain: 1) a means to understand how the micropump output performance for both flow rate and backpressure, can be optimized for any particular microfluidic application, 2) an experimentally characterized micropump performance curve/s, 3) an experimentally characterized system curve, 4) the maximum power output of the micropump, and 5) a means to acquire a quantitative measure of the suction lift requirements associated with rodent brain direct-sampling neuroscience experiments. A control volume analysis is provided, to additionally articulate and facilitate discussion of the direct-sampling methodology. Preliminary pilot study direct-sampling data is also provided, as a means to justify and prove viability of the direct-sampling technique, for future characterization and optimization direct-sampling CE-LIF neuroscience studies.