Microfluidic biochemical analysis system with electro-osmotic pump and thermally responsive polymer valve

Integrated microfluidic systems require multiple pumps and valves to be operated concurrently and sequentially. These components must be easy to fabricate and integrate, and be reliable. In this dissertation a surface micromachined porous polymer electro-osmotic pump (pp-EOP) and thermally responsive polymer valve have been developed to serve these purposes.; The electro-osmotic pump uses a porous polymer (with an average pore radius of ∼150 nm) plug, eliminating pressure effects while allowing electro-osmotic flow in a parylene channel with embedded planar or vertical electrodes. The vertical electrode device at 3 V DC generates 4.8 nL/min volumetric flow rate and a maximum pressure of 1541 Pa. A new drive, periodic, asymmetrical, net zero average AC current signal at around 1 Hz frequency has been tried to prevent bubble generation while producing non-zero average voltage and thus a net lateral motion. However, this new drive is found to have reliability and repeatability issues in long term.; A liquid bridge configuration has been developed to allow the application of DC voltages to drive pp-EOPs without any bubble generation problems. The electrodes near the main channel are connected to it with narrow porous plug branches allowing current conduction but constituting high hydraulic resistance to liquid flow. This device gives a flow rate of 1.76 nL/min and a maximum pressure head of 1673 Pa at 50 V DC.; High frequency AC drive of an electro-osmotic pump has been achieved by rectifying the flow with zeta potential modulation of surfaces responsible for electro-osmotic flow with an insulated gate electrode in synchronous with the driving electric field modulation. This way net flow is achieved without bubble generation with closely spaced electrodes inside the main channel. A simple device fabricated to prove the concept gives a flow rate of 16 nL/min with a pressure head of 2.3 Pa in response to a 1 KHz AC square signal with a magnitude of 17 volts.; Finally, a thermally responsive polymer has been surface micromachined by using spinning and/or casting for thin film formation and lithography for patterning. It shows repeatable and around 100% volume change by changing the liquid temperature from 25 to 10°C, thus a big potential to realize valves with low leak. This polymer is integrated into parylene channels with embedded microheaters to form a valve.