Large distance liquid pumping by AC electro-osmosis for the delivery of biological cells and reagents in microfluidic devices

摘要

Liquid pumping, mixing and biological cells/reagents delivery in micro- or nano-liter volume is critical in lab-on-chip systems. We describe a novel AC electro-osmosis device for delivering reagents/cells over large distances without a global pressure gradient. Our device features facile transport range scalability in x- and y-axes, using continuous flow in a serpentine microchannel realized by microelectrode pairs arrayed in a unique antiparallel-asymmetric configuration. Co-planar microelectrodes on glass substrate are fabricated from gold with chromium as seed layer using micro-electromechanical system (MEMS) technology. Sealed upon the micro-electrodes is an open-ended serpentine microchannel having width 80μm and depth 45μm; formed by micromolding PDMS with a silicon-based mold. AC signals at 3.5V_(PP) and 0.5V DC offset is used to energize the microelectrodes, and polystyrene beads with diameter 5.0μm are used as tracer particles to visualize flow. Maximum velocity of 871 μm/s was recorded using AC signals at 8 kHz. The ease of scaling up transport distance range in 2-axes is unique to our device. Scalability in x-axis is achieved by varying the number of microelectrode pairs; and in y-axis by varying the number of microelectrodes iterations and the corresponding number of turns in the serpentine microchannel. Being scalable in transporting fluidic volume with high efficiency under small driving voltages makes our device suitable for miniaturization in a micro-total-analytical-system. Our device could be applied towards multiple point reagents, biological cells and particles delivery and mixing in a lab-on-chip.