Abstract
Deterministic lateral displacement (DLD) systems structure suspension flow in so called flow lanes. The width of these flow lanes is crucial for separation of particles and determines whether particles with certain size are displaced or not. In previous research, separation was observed in simplified DLD systems that did not meet the established DLD geometric design criteria, by adjusting the outflow conditions. We here investigated why these simplified DLD systems are able to displace particles, by experimentally investigating the hydrodynamics in the device. Flow lanes were visualized and the local flow velocities were measured using µPIV and compared with 2D fluid dynamics simulations. The size of the flow lanes strongly correlates with the local flow velocity (Vy and Vx), which depends on the hydrodynamics. Therefore, the geometric design criteria of DLD devices is in fact just one method to control the local hydrodynamics, which may also be influenced by other means. These findings give a new perspective on the separation principle, which makes the technique more flexible and easier to translate to industrial scale.
Highlights
Separating neutrally buoyant suspensions of micron-sized particles (1–10 μm) is not a trivial operation
The flow lane width was visualized using the trajectories of individual tracer particles and the most outward pathline that enters or exits this gap is outlined by a red line
An in-depth characterization was done on the flow lane sizes in asymmetric, sieve-based deterministic lateral displacement (SLD) devices
Summary
Separating neutrally buoyant suspensions of micron-sized particles (1–10 μm) is not a trivial operation. Separation in DLD (planar geometry) and SLD systems (non-planar geometry) relies on particle-obstacle interactions that laterally displace particles in the fluid from their streamlines, out of the critical flow lane[15]. If the particle radius is smaller than the flow lane width, this particle (white) may still be displaced but not sufficient to cross over to the flow lane and will stay in its initial flow lane (Fig. 1B,D and supplementary video) This means that the critical particle diameter is controlled by the width of the flow lanes, which makes precise control of the flow essential. The influence of the geometric design criteria of DLD arrays on the critical particle diameter has been thoroughly investigated The hydrodynamics in such systems have, not received much attention, it is known to influence the size of the flow lanes.
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