Design Simulation and Fabrication of Micromixers and Microvalves for Lab on a Chip Devices

Abstract

Lab-on-a-Chip diagnostic devices can be used as quick tools to identify the onset of diseases at an early stage. In order to develop such devices, it is essential to develop efficient microfluidic components, like micromixers and microvalves, that can perform the conventional laboratory procedures on a miniaturized chip. These microfluidic components can be integrated into a common platform as required for Point-of-Care diagnosis. The microfluidic components must be cost-effective, automated, and portable so that they can be used in any corner of the world, by a common man, thus improving the quality of living. newlineIn this thesis, microfluidic components like micromixers, microvalves and serial dilution networks were designed, simulated, fabricated and tested for application in Lab-on-a-Chip device development. Simulation studies were used to optimize the design of the microfluidic components, and the optimized design was fabricated by photolithography using SU-8 followed by soft lithography using PDMS. The micromixers were developed based on meander microchannels with alternately varying cross-sectional diameter. The micromixers were used to create a medium-throughput lab-on-a-chip device for the mass screening of the diabetic population. An improved micromixer using ridges incorporated meander channels was also developed and tested. Meander channels with ridges could provide a mixing efficiency higher than 90% in less than 2 mm compared to meander channels without ridges which required a length of 27 mm. A serial dilution network for obtaining desired concentration at the outlet was developed using a hydraulic-electric circuit analogy. The ability of the dilution network to generate a logarithmic concentration profile and user-defined concentration at the outlet was demonstrated. The performance of the dilution network was validated by absorbance studies using safranin dye solution. Microvalves for the control of multiple fluids were developed based on the concept of electromagnetic actuation...