Diseases are often diagnosed by detection of disease-specific biomarkers in fluid samples. However, many state-of-the-art detection methods require a lab with complex machinery, trained operators, and/or lengthy analysis time. In contrast, point-of-care (POC) devices are brought to the patient's location, they are easy to use, and results are obtained almost immediately. Many current POC devices are too difficult to be used without a skilled assistant, and although many are able to detect analytes above a threshold value, they give little or no quantitative information. This work presents the development of polymer-based microfluidic devices capable of sensing and quantifying biomarkers in fluid samples in a straightforward manner using a novel biomarker assay termed "flow valve diagnostics". In this assay, an antibody-modified polydimethylsiloxane (PDMS) microchannel constricts due to the binding force between antibodies and antigens, stopping fluid flow. The flow distance is measured and correlated to antigen concentration. This detection method is an improvement over other methods because it is an innovative, non-instrumented, label-free, easy-to-use approach. These devices are small, portable, disposable, inexpensive, and thus ideal for use in POC testing. I have successfully fabricated flow valve devices with standard micromachining techniques, including photolithography, replica molding with PDMS, and plasma oxidation. Following fabrication, I compared two methods for attaching receptor biomolecules (e.g., antibodies) to the microchannel surfaces: non-specific adsorption and silanization with 3-glycidoxytrimethoxypropylsilane (GOPS). I used laser-induced fluorescence to determine that silanization with GOPS was the better method for biomolecule attachment. Finally, I tested antibody-modified flow valve devices with target antigens to determine if the antibody/antigen binding force was strong enough to cause channel pinching and flow stoppage. By modifying the device design and using higher antigen concentrations, I was able to show that flow valve devices can detect antigens in a concentration-dependent manner. Future work to improve the device design and to modify and test these devices with different receptor/target pairs will bring flow valve diagnostics closer to becoming a valuable asset in biomarker detection and POC testing.



College and Department

Physical and Mathematical Sciences; Chemistry and Biochemistry



Date Submitted


Document Type





biomarker detection, point-of-care testing, label-free, quantitative, PDMS