Our efforts are focused on development of “sample-in, result-out” type of lab-on-a-chip systems. Although there are several interesting examples of lab-on-a-chip systems, there is still need for well integrated, robust and all-in-one systems. We are interested in developing true lab-on-a-chip systems that can operate with minimal user intervention. We are developing these systems for biochemical analysis. Below are some examples of such projects.
We devised a microfluidic system that incorporates electroosmotic pumps, a concentration gradient generator and a fish cell line (rainbow trout gill) to perform toxicity testing on immobilized fish cells. The system consists of three mechanical components: (1) a toxicity testing chip containing a microfluidic gradient generator which creates a linear concentration distribution of toxicant in a cell test chamber, (2) an electroosmotic (EO) pump chip that controls the flow rate and operation of the toxicity chip, and (3) indirect reservoirs that connect the two chips allowing for the toxicant solution to be pumped separately from the electroosmotic pump solution. A lethality test was performed with this system setup using a rainbow trout gill cell line (RTgill-W1) as the test cells and sodium dodecyl sulfate as a model toxicant. Sodium dodecyl sulfate was applied at varying concentrations for 1 hr to the attached cells, and the results were quantified using a viability cell assay.
We developed a fully integrated polydimethylsiloxane (PDMS)/modified PDMS membrane/SU-8/ quartz hybrid chip for protein separation using isoelectric focusing (IEF) mechanism coupled with whole-channel imaging detection. This microfluidic chip integrates three components into one single chip: (i) modified PDMS membranes for separating electrolytes in the reservoirs from the sample in the microchannel and thus reducing pressure disturbance, (ii) SU-8 optical slit to block UV light (below 300 nm) outside the channel aiming to increase detection sensitivity, and (iii) injection and discharge capillaries for continuous operation. Integration of all these components on a single chip is challenging because it requires fabrication techniques for perfect bonding between different materials and is prone to leakage and blockage. Our chip was tested by performing protein and pI marker separation. The separation results obtained in this chip were compared with that obtained in commercial cartridges. Side-by-side comparison validated the developed chip and fabrication techniques.