Surface Acoustic Wave-Actuated Cell Sorting and Enantiomer Separation



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This dissertation is focused on the mathematical modeling and numerical simulations of cell sorting and enatiomer separation using surface acoustic wave-actuated fluid flow.

We model a high throughput sorting of two different types of biological cells (type I and type II) by a biomedical micro-electro-mechanical system (BioMEMS) whose operating principle depends on surface acoustic wave (SAW)-manipulated fluid flow in a microchannel. The BioMEMS consists of a separation channel with three inflow channels for injection of the carrier fluid and the cells, two outflow channels for separation, and an interdigital transducer (IDT) close to the lateral wall of the separation channel for generation of the SAWs. The cells can be distinguished by fluorescence. The inflow velocities are tuned such that, without SAW actuation, a cell of type I leaves the device through a designated outflow channel. However, if a cell of type II is detected, the IDT is switched on and the SAWs modify the fluid flow such that the cell leaves the separation channel through the other outflow boundary.

Enantiomers are chiral objects such as chemical molecules that can be distinguished by their handedness. They typically occur as racemic compounds of left- and right-handed species which may have completely different properties. Therefore, in applications such as drug design in pharmacology, enantiomer separation is an important issue. In this dissertation, we present a new technology for enantiomer separation by surface acoustic wave generated vorticity patterns consisting of pairwise counter-rotating vortices in a carrier fluid. The enantiomers are injected onto the surface of the fluid between two counter-rotating vortices such that right-handed (left-handed) enantiomers are attracted by left-rotating (right-rotating) vortices.

For modeling and numerical simulation of the cell sorting and enantiomer separation process we use the Finite Element Immersed Boundary (FE-IB) method, which relies on the solution of a coupled system consisting of the incompressible Navier-Stokes equations, and the equations of motion of the immersed structures described with respect to an Eulerian and a Lagrangian coordinate system.

The results of the numerical simulation are compared with experimentally obtained results, and they are in excellent agreement.



Cell sorting, Enantiomer separation, Surface acoustic waves, Finite element immersed boundary method