Double-L injection technique for high performance capillary electrophoresis detection in microfluidic chips

This paper reports low-leakage injection techniques to deliver sample plugs within double-T-form electrophoresis microchips. Experimental and numerical investigations are used to predict and evaluate the leakage behavior during electrokinetic driving of the sample plugs. The principal material transport mechanisms including traditional cross-form, electro-floating, diffusion sampling injection techniques are discussed in this study. A simple and precise double-L injection technique that employs electrokinetic manipulations to avoid sample leakage within the microchip is also reported. The method needs only one electrical control point during injection and separation, so the control system can be smaller and cheaper. Experimental and numerical results show the proposed injection technique is able to reduce sample leakage significantly. No leakage happens after 16 sample injections using the double-L injection method while leakage usually happens using the traditional cross-form injection technique. The double-L injection technique proposed in this study has a great potential for use in high-precision analysis applications utilizing chip-based capillary electrophoresis.