A Micro-aspirator Chip Using Vacuum Expanded Microchannels for High-throughput Mechanical Characterization of Biological Cells
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This thesis presents the development of a micro-aspirator chip using vacuum expanded microchannels for mechanical characterization of single cells. Mechanical properties of cells can offer valuable insights into the pathogenic basis of diseases and can serve as a biomarker to identify cells depending on disease state, and thus have the potential for use in human disease diagnostic applications. Micropipette aspiration and atomic force microscopy (AFM) are the most commonly used techniques for measuring mechanical properties of single cells. Though powerful and versatile, both methods have two drawbacks. First, micromanipulation of glass micropipettes and AFM tips require expertise and extensive operator skills. Second, the serial manipulation process severely limits the throughput. Although recently reported microfluidic micropipette device showed the potential of microfluidic chip type micropipette aspiration, difficulty in cell trapping and unnatural cell deformation remain to be solved. In order to address these limitations, a high-throughput micro-aspirator chip, which can deliver, trap, and deform multiple cells simultaneously with single-cell resolution without skill-dependent micromanipulation was developed. The micro-aspirator chip is composed of 20 arrays of cell traps and aspiration channels. The principle of cell trapping is based on differences in flow resistance inside the microfluidic channels. Once the first cell trap is filled with a cell, the next cell coming in passes by the trap and is captured in the next trap. After all traps are filled with cells, negative pressure can then be applied to the integrated aspiration channels using hydrostatic pressure. The aspiration channels are positioned at the center of a trapped cell both in vertical and horizontal directions to obtain a good seal just like a traditional micropipette, a design made possible through a vacuum expanded raised microfluidic channel fabrication technique. Device operation was demonstrated using HeLa cells. The cell trapping efficiency was almost 100 percent. Using this device, Young's modulus of 1.3 ? 0.8 kPa (n = 54) was obtained for HeLa cells. Device to device variation was less than 15.2 percent (n = 3), showing good repeatability of the device. No dependence of the Young's modulus on the cell diameter was found.