A microfabricated CE chip for DNA pre‐concentration and separation utilizing a normally closed valve

A simple, sequential DNA pre‐concentration and separation method by using a micro‐CE chip integrated with a normally closed valve, which is activated by pneumatic suction, has been developed. The CE chip is fabricated using PDMS. A surface treatment technique for coating a polymer bilayer with an anionic charge is applied to modify the surface of the microchannel. A normally closed valve with anionic surface charges forms a nanoscale channel that only allows the passage of electric current but traps the DNA samples so that they are pre‐concentrated. After the pre‐concentration step, a pneumatic suction force is applied to the normally closed valve. This presses down the valve membrane, which reconnects the channels. The DNA samples are then moved into a separation channel for further separation and analysis. Successful DNA pre‐concentration and separation has been achieved. Fluorescent intensity at the pre‐concentration area is increased by approximately 3570 times within 1.9 min of operation. The signals from the separation of ϕX174 DNA/HaeIII markers are enhanced approximately 41 times after 100 s of pre‐concentration time, as compared with the results using a traditional cross‐shaped micro‐CE chip. These results clearly demonstrate that successful DNA pre‐concentration for signal enhancement and separation analysis can be performed by using this new micro‐CE chip.

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