| Summary: | 碩士 === 國立成功大學 === 化學工程學系 === 104 === Micro sensing devices deliver suspended particles to sensors through microchannels. Prior to sensing, the particles should be assembled by microfluid. This thesis investigates the assembly of suspended particles in rectangular microchannels and proposes a feedback control strategy based on the adjustment of electroosmotic flow.
The thesis derives an analytical solution for the stream function of electroosmotic flow in a rectangular microchannel, which allows the boundary conditions of a confined region and arbitrary slip velocity distributions. The solution is an infinite series expansion and is composed of eigenfunctions that confine fluid flow. The expansion coefficients must satisfy the boundary slip conditions. However, the expansion coefficients are difficult to converge, causing inaccuracy in calculating their values as well as poor convergence of the analytical solution in the vicinity of the boundaries. To solve this difficulty, each expansion coefficient is divided into a difficult-to-converge part and an easy-to-converge part. For specific slip velocity distributions, the periodicity of all difficult-to-converge parts can be identified and their values can be calculated. As a result, the accurate values of the easy-to-converge parts can be obtained easily.
Electroosmotic microvortices together with short-range force could form a stagnation point on a surface to create the effect of particle assembly at that point. However, the efficiency of particle assembly is often not high because of the difficulty for particles escaping from the center of a microvortex and long travelling paths via electroosmotic flow. This thesis applies the derived analytical solution to simulate the feedback control problem of particle assembly. The proposed feedback control strategy combines the fundamental microvortices and short-range force, employs particles close to the centers of microvortices as the controlled objects, and chooses different points as virtual targets. Eventually, the control strategy can achieve fast particle assembly at the stagnation point.
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