Prasanna Thwar

Development of a digital microfluidic platform for point of care testing

Point of care testing is playing an increasingly important role in improving the clinical outcome in health care management. The salient features of a point of care device are rapid results, integrated sample preparation and processing, small sample volumes, portability, multifunctionality and low cost. In this paper, we demonstrate some of these salient features utilizing an electrowetting-based Digital Microfluidic platform. We demonstrate the performance of magnetic bead-based immunoassays (cardiac troponin I) on a digital microfluidic cartridge in less than 8 minutes using whole blood samples. Using the same microfluidic cartridge, a 40-cycle real-time polymerase chain reaction was performed within 12 minutes by shuttling a droplet between two thermal zones. We further demonstrate, on the same cartridge, the capability to perform sample preparation for bacterial infectious disease pathogen, methicillin-resistant Staphylococcus aureus and for human genomic DNA using magnetic beads. In addition to rapid results and integrated sample preparation, electrowetting-based digital microfluidic instruments are highly portable because fluid pumping is performed electronically. All the digital microfluidic chips presented here were fabricated on printed circuit boards utilizing mass production techniques that keep the cost of the chip low. Due to the modularity and scalability afforded by digital microfluidics, multifunctional testing capability, such as combinations within and between immunoassays, DNA amplification, and enzymatic assays, can be brought to the point of care at a relatively low cost because a single chip can be configured in software for different assays required along the path of care.

Digital microfluidic biochip design for protein crystallization

Proteins crystallization is a commonly used technique for protein analysis. It predicts the three-dimensional (3D) arrangement of the constituent amino acids, which indicates the specific biological function of a protein. Protein crystallization experiments are typically carried out in well-plates; as a result, these experiments are slow, expensive, and errors are likely due to the need for repeated human intervention. Recently, droplet-based digital microfluidics has been used for executing protein assays on a chip. Protein samples are enclosed in droplets, which are manipulated using the principle of electrowetting-on-dielectric. Digital microfluidics offers a high degree of automation, and it significantly reduces the volumes of proteins required for crystallization. We present the design of a multi-well plate microfluidic biochip for protein crystallization, which can transfer protein samples, prepare candidate solutions, and carry out crystallization automatically. To reduce the manufacturing cost of such devices, we present an efficient algorithm to generate a pin-assignment plan for the proposed design. The resulting biochip enables control of a large number of on-chip electrodes using only a small number of pins.