Development of Temperature Measurement and Control of 3D Printed Microfluidic Devices Towards Biomolecular Analysis

Microfluidics are devices with channels or reservoirs that have dimensions in the range of micrometers. They have an increasing role in biological analysis processes due to their ability to use very small sample volumes. Many microfluidic processes rely heavily on precise temperature measurement and control. Advances in 3D printing have led to high resolution digital light processing stereolithography (DLP-SLA) printers capable of using bio-compatible materials, available at BYU. This custom 3D printer has a resolution of 7.6 µm in the XY plane and 10 µm in the Z axis. Combined with a custom-made resin, we can produce microfluidic features as small as 18 µm x 20 µm. These advances allow for more complex internal geometries with multiple overlapping channels. As the internal geometry becomes more complex, traditional microfluidic temperature measurement tools are limited in their application. This dissertation considers the use of temperature sensitive quantum dots (QDs), nano-scale semiconductor crystals that fluoresce, as an internal temperature measurement tool. This work presents two types of QDs, CdTe and CdSe/ZnS, and their performance as a temperature sensor by relating either photoluminescence peak intensity to temperature or a feed-forward neural network combining multiple features of the fluorescent spectra to temperature. Additionally, 3D printing's ability to create arbitrary 3D structures with an arbitrary 3D orientation, as opposed to traditional microfluidic fabrication methods, enables new three-dimensional heater geometries to be created that provide better internal heat distributions. We present new heater geometries only feasible through 3D printing that can isothermally heat a precisely defined volume. One such design is for a device that can control the temperature of a 5 µL internal chamber to within 0.2°C. This last design is aimed at a new microfluidic device for high resolution DNA melt curve analysis for the detection of single nucleotide polymorphisms. This set of tools we developed will enable the expansion of 3D printed microfluidics beyond the current planar limitations and fluid flow processes into temperature sensitive analyses.