Numerical Studies of Injection Process Control With Spatial Gradients of Electrical Conductivity

The systematic design and precise control of the microfluidic dispenser (crossing microchannels etched into a plastic or glass plate) is key to the performance of many lab-on-a-chip devices. The fundamental understanding of the complicated electrokinetic phenomena in microfluidic dispensers therefore is necessary. In the literature, a few theoretical models studying the transport phenomena in similar crossing microchannels didn’t consider the spatial gradients of conductivity due to its complexity. A new theoretical model was developed in this paper to simulate the transport phenomena in a microfluidic dispenser with the consideration of a large range of spatial gradient of electric conductivity. This developed model was used to simulate the potential field, flow field, and concentration field of the injection processes where the conductivity of the sample-carrying buffer differs significantly from that of the driving buffer. The transport phenomena are found to be very sensitive to the conductivity difference between the sample-carrying buffer and the driving buffer. The developed model can be employed to find the optimal voltages for controlling the dispensed sample size and to provide guidance for designing such a microfluidic dispenser in lab-on-a-chip devices.