Porous Structures for Enhanced Electrokinetic Point-of-Care Diagnostics

Abstract

The recent outbreak of SARS-COVID-2 virus has emphasized the necessity for low-cost, portable, rapid, and sensitive biomolecule handling and detection systems for effective monitoring and management of pandemics and other healthcare emergencies. Portable sensing systems capable of detecting and quantifying molecular binding interactions are also crucial in applications such as food and environmental safety, biopharmaceutical development, and basic biological research. Herein, I present three novel microfluidic technologies that have immediate applications in fields such as disease diagnostics, microbial contamination, warfare detection, food, and public health monitoring. In the first project, I present a novel, label-free method for determining protein/ligand binding kinetics in liquid phase. This method transduces a molecular scale binding event occurring at a liquid-liquid interface into a macroscopic liquid motion that serves as a sensitive biosensing transducer by leveraging AC electrokinetics. In the second project, I describe a rapid, low-cost, and scalable paper-PDMS fabrication technique called microfluidic pressure in paper (μPiP) that reduces fabrication costs and de-risks electrokinetics-based microfluidic device commercialization. I have used this technique to develop a low cost, easy-to-use red blood cell deformability assay. Additionally, I have leveraged the insulating properties of paper fibers to demonstrate insulator-based dielectrophoresis (iDEP) in paper for the first time. Using Micro-CT scan imaging, I have developed a finite-element model that can predict DEP force growth dynamics and trapping mechanisms within paper pores. I have used a pulsed DC field to trap polystyrene particles, cells, and nucleic acid within paper. This technique is currently being used to trap DNA from biofluids for liquid biopsy applications, and if successful, it will democratize cancer treatment by significantly reducing cancer monitoring costs. Finally, in the third project, I present a cost-efficient, scalable, and sensitive microfluidic sensor that uses piezoresistive conductive microfluidic membranes to measure local pressure change. The sensor costs several orders of magnitude less than existing commercial platforms and can monitor local fluid pressures and calculate flow rates based on the pressure gradient.