The Design and Evaluation of a Microfluidic Cell Sorting Chip
Numerical and experimental results are used to evaluate the sample focusing element for controlled cell dispensing, the sorting configuration for target cell collection, and the flow elements for reduced pressure effects and prevention of flow blockages. Compact models are adapted to solve the potential field and flow field in the chip and to predict the focused sample stream width. A commercial CFD package is used to perform 2-D simulations of the potential, velocity, and concentration fields. A fluorescence microscopy visualization system is implemented to conduct experiments on several generations of chip designs. The data from sample focusing experiments, performed with fluorescent dye samples, is analyzed using a Gaussian distribution model proposed in this work. A technique for real-time monitoring of fluorescent microspheres in the microfluidic chip enables the use of dynamic cell sorting to emulate fully autonomous operation. The performance values obtained from these experiments are used to characterize the various design configurations.
Sample focusing is shown to depend largely on the relative size of the sheath fluid channel and the sample channel, but is virtually independent of the junction shape. Savings in the applied potential can be achieved by utilizing the size dependency. The focusing performance also provides information for optimizing the widths of the channels relative to the cell size. Successful sorting of desired cells is demonstrated for several designs. Key parameters that affect the sorting performance are discussed; a design employing the use of supplemental fluid streams to direct the particle during collection is chosen due to a high sorting evaluation and a low sensitivity to flow anomalies. The necessary reduction of pressure influences to achieve reliable flow conditions is accomplished by introducing channel constrictions to increase the hydrodynamic resistance. Also, prolonged operation is realized by including particle filters in the proposed design to prevent blockages caused by the accumulation of larger particles.
A greater understanding of the behaviour of various components is demonstrated and a design is presented that incorporates the elements with the best performance. The capability of the microfluidic chip is summarized based on experimental results of the tested designs and theoretical cell sorting relationships. Adaptation of this chip to a stand-alone, autonomous device can be accomplished by integrating an optical detection system and further miniaturization of the critical components.
School:University of Waterloo
School Location:Canada - Ontario
Source Type:Master's Thesis
Keywords:microfluidics cell sorter lab on a chip mechanical engineering
Date of Publication:01/01/2007