G. Hawkins, D. Sanchez, H.S. Hinnen, A. Day, A.T. Woolley, G.P. Nordin, and T. Munro
Brigham Young University,
Keywords: microfluidics, 3D printing, fluorescent thermometry, isothermal heating
Summary:Many microfluidic processes rely heavily on precise temperature control. Two aspects of temperature control we are investigating are microfluidic heating and temperature sensing for improved temperature uniformity inside microfluidic devices. Though internally contained heaters have been developed using traditional fabrication methods, they are limited in their ability to isothermally heat a precisely defined volume. Advances in 3D printing have led to high resolution printers capable of using bio-compatible materials and achieving internal feature resolutions near 20μm. 3D printing’s ability to create arbitrary 3D structures as opposed to traditional microfluidic fabrication methods enables new three-dimensional heater geometries to be created. As examples, we demonstrate three new 3D heater geometries: a non-planar serpentine channel, a tapered helical channel, and a diamond channel. These new geometries are shown through finite element simulation to isothermally heat microfluidic channels of cross section 200 μm x 200 μm with 0.1°C temperature difference along up to 91% of a 10 mm length. The finite element models are also verified through fabrication and experimental testing of these designs. Another advantage of 3D printing is the ability to place a temperature sensor in an arbitrary geometry around the region of interest. Temperature sensitive fluorescent material can then be dispersed in a specific geometry to produce a temperature map rather than a single temperature value. Temperature sensitive quantum dots can be dispersed in microfluidic channels and sealed with resin. Work is being done to find a quantum dots and resin formulation that provide long-term fluorescent signal stability. Improving internal heater geometry and producing a temperature map aid in improving the temperature uniformity inside a microfluidic device, which together improve temperature control.