A numerical model has been developed and is used to study the loading and dispensing processes in on-chip cross-linked microchannels. The electrokinetic transport characteristics and the roles of species’ electrophoretic mobilities and diffusion coefficients on the electrokinetic flow are revealed. A study is also performed on an implementation of multi-stage injection. The study of conventional one-step injection and separation is performed and helps construct a distinct understanding of the processes. Species movement and sample plug development with diffusion are examined; results include concentration profiles and contour plots over a range of injection and separation time. Real-time monitoring of different species’ movements is performed for injection guidance. Some limitations of the separation process are presented with potential solutions, such as the removable tail effect and exceptional quick diffusion. Using innovative dynamic control, efforts are made to control the flow and species transport for improved sample plugs, which is key to achieving excellent electrophoretic separation. Through a series of multi-step injection schemes, four typical sample plugs are produced with specific attributes such as reduced dispersion leakage, desirable sample plug size, enhanced shape, etc. Comparisons of conventional and the proposed methods are performed. Typical resulting sample plugs are evaluated using the two developed parameters of resolution and detectability for numerically simulated separation processes. Depending on requirements, one can generate some specific sample plugs through this multi-step dynamic injection method. The resulting understanding will assist in the design of microfluidic devices for separation by providing insight into the process influences and controls and by identifying areas for further research.

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