Document Type


Date of Award


Degree Name

Doctor of Philosophy in Mechanical Engineering - (Ph.D.)


Mechanical and Industrial Engineering

First Advisor

Eon Soo Lee

Second Advisor

Chao Zhu

Third Advisor

Zhiming Ji

Fourth Advisor

Jacob Timothy Trevino

Fifth Advisor

Dibakar Datta


The integration of the microfluidics to the biosensor has growing demand with favorable conditions such as reduced processing time and low reagent consumption. The immuno biosensing with the microfluidic platform helped to make the electrochemical biosensing assays portable due to which this sensing mechanism can be easily implemented in point of care devices. The implementation of the biosensing in the microchannels significantly reduces the sample requirement form milli liter (mL) to micro liter (uL), and thus leads to low volume sample requirement during the sensing. The primary factors contributing to the microfluidic biosensors performance are probe immobilization, specific binding and fundamental limits of probe affinity. Due to the tight confinement of the flow of the antigen solution in the microscale, the flows in the microchannel exert high shear stresses on the surface of the microchannel and influence the stability of the immobilized antibodies on the surface. So the study of the sensing signal response during the flow condition attracts many researchers to develop novel techniques of antibody immobilization for enhanced stability.

The study of the sensitivity variation of CA-125 antigens detection using interdigitated electrodes, 'with' and 'without' microfluidic flow of CA-125 antigens is performed. The CA-125 antibodies are covalently bonded to the interdigitated electrodes using the Thiourea and Glutaraldehyde. When the biofluid sample (CA-125 antigens with phosphate buffer saline solution) is passed on the CA-125 antibodies that are immobilized on the gold interdigitated electrodes, the capacitance variation of the sensing circuit is caused due to the antigen antibody interaction. However, the capacitance measured during CA-125 antigen-antibody interaction with the microfluidic flow condition is lower than ?without microfluidic flow? condition due to the instability of the immobilized antibodies on the sensing surface that is caused by the shear stress during the microfluidic flow.

The study of sensitivity variation of CA-125 detection 'with' and 'without' microfluidic flow of CA-125 antigens is performed using the gold nano particles on the interdigitated electrodes. The carboxylic gold nanoparticles forms covalent bond with the antibodies and the orientational freedom of gold nano particles helps in higher quantity of antibodies immobilized. Though the gold nano particles provide higher stability to the antibodies when compared to the Glutaraldehyde.

The future progress of this research will be detection of multiplex antigens with multiple concentrations in order to enhance the microfluidic biosensing mechanisms to serve in the point-of-care devices in diagnosing targeted disease antigens with high sensitivity.



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