There are many advantages to integrating simple passive-fluidic elements in microfluidic devices that manipulate particles. One of the barriers for this integration is the compatibility of their typically continuous flow format with some device’s droplet or non-continuous operation. For example, many DNA analysis devices use discrete droplets to perform the series of operations from pathogen extraction and sample purification to target DNA amplification and product detection. The steps of this diagnostic process have different processing times from seconds to close to an hour, and each step needs to be individually optimized for best results.. Incorporating continuous flow, passive-fluidic techniques in this chain can constrain all the steps to continuous flow and places restrictions on both the design and the operation of the device.
In this presentation, we will describe a passive fluidic technique that generates one-way particle transport using oscillatory flow instead of constant continuous flow. The technique combines the asymmetric particle capturing of an asymmetric trap array and the oscillation of a fluid stream to produce a net positive displacement of micro-particles. This particle displacement was achieved with zero net displacement of the fluid. The reversibility of low Reynolds number flow was overcome by using trap/particle physical collisions. The diameter range of the particles and the minimum amplitude of fluid oscillation necessary for one-way particle transport at a given array dimension was theoretically determined using mass balance equations and computational fluid simulations. The asymmetric trap array satisfying the design guideline successfully achieved deterministic one-way particle transport of 20.3 µm polystyrene beads. Practical applications such as particle segregation and particle concentration can be constructed using this one-way particle transport.
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