Category: Micro- and Nanotechnologies
Measuring the temperature of a sample is a fundamental need in many biological and chemical processes. When the volume of the sample is on the microliter or nanoliter scale (e.g., cells, microorganisms, precious samples, or samples in microfluidic devices), accurate and automated measurement of the sample temperature becomes challenging. In this work, we demonstrate a technique for accurately determining the temperature of microliter volumes using a simple 3D-printed microfluidic chip and a custom software tool. We accomplish this by first filling "microfluidic thermometer" channels on the chip with substances with precisely known freezing/melting points. We then use a thermoelectric cooler to create a stable temperature gradient along these channels. A custom software tool is then used to a find the locations of solid-liquid interfaces in the thermometer channels; these locations have known temperatures equal to the freezing/melting points of the substances in the channels. The software then automates the temperature measurement process by using the locations of these interfaces to calculate the temperature at any desired point on-chip. Using this approach, the temperature of any microliter-scale on-chip sample can be measured with an uncertainty of about a quarter of a degree Celsius. As a proof-of-concept, we use this technique to measure the unknown freezing point of a 50 microliter volume of solution and demonstrate its feasibility on a 400 nanoliter sample. Additionally, this technique can be used to measure the temperature of any on-chip sample, not just near-zero-Celsius freezing points. We demonstrate this by using an oil that solidifies near room temperature (coconut oil) in a microfluidic thermometer to measure on-chip temperatures well above zero Celsius. By providing a low-cost, simple, and automated way to accurately measure temperatures in small volumes, this technique should find applications in both research and educational laboratories.
Brittney McKenzie– PhD Candidate, University of California, Riverside, Riverside, CA
University of California, Riverside
Brittney McKenzie is a Bioengineering Ph.D. Candidate in Dr. William H. Grover's lab at the University of California - Riverside, where she and her colleagues develop intruments that examine and analyze intrisic physical properties of samples. She earned her B.S. in Bioengineering and minor in Applied Mathematics at the University of Washington in 2013 and her M.S. in bioengineering from the University of California - Riverside in 2015.