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theses

Deterministic Lateral Displacement (DLD) exploits the experimental observation that in microfluidics, particles of different sizes forced through a periodic array of cylindrical posts may migrate in different directions thus leading to separation. In this dissertation, we propose various modifications on DLD systems and discuss the potential of using one of the more radically modified DLD systems to filter particulate matter air pollution. We first propose a flow-driven DLD system with a rotating circle at the center of the obstacle array. This model system can be easily reconfigured to establish an arbitrary orientation between the average flow field and the array of obstacles comprising the stationary phase (forcing angle). We show that this reconfigurable design preserves the size separation functionality of traditional DLD device and hugely improves the reusability of DLD devices. We then extend the length of the posts in the obstacle array and construct a 3D-DLD setup which allows the particle to move not only in-plane (in the basal plane of the obstacle array) but also out-of-plane (along the direction of the posts). We show that the (projected) in-plane motion of the particles is completely analogous to that observed in 2D-DLD systems. More importantly, we observe significant differences in the out-of-plane displacement depending on particle size for certain orientations of the driving force. Therefore, taking advantage of both the in-plane and out-of-plane motion of the particles, it is possible to achieve the simultaneous fractionation of a polydisperse suspension into multiple streams. Last, we present a radical departure from traditional system and use an array of anchored liquid-bridges as the stationary phase in the DLD device. We show that the non-linear particle dynamics observed in traditional DLD systems is also present in the anchored-liquid case, enabling analogous size-based separation of suspended particles. Interestingly, preliminary experiments show that the proposed liquid DLD system can function excellently well as a particulate matter air filtration device when subjected to a cross directional particle-laden flow. In particular, we uncover the deciding factors, namely particle incoming offset and Stokes number, related to particle capture efficiency and lay out future plans to further the exploration in the domain of air filtration using arrays of anchored liquid bridges.

ETD_9336

doi:10.7282/T3FT8QP3

Ph.D.

Includes bibliographical references

by Siqi Du

This work was partially supported by the National Science Foundation Grant no. CBET-1339087.

ETD doctoral

The author owns the copyright to this work.