UC Riverside

Tools for identifying substances are important in many different fields and have a wide range of applications. Conventional analytical tools and instruments such as spectroscopy and chromatography systems are exceptional in their ability to measure and analyze samples. However, the cost, size, and complexity of these instruments limit their use in important applications in resource-limited settings. While ''frugal science''— science solutions that prioritize both cost and function— has made strides in expanding access to healthcare and research, there is still an unmet need for more low-cost and accessible research and analytical tools. In this work, I develop simple, low-cost, and effective analytical tools on microfluidic platforms that utilize changes in the physical properties of substances to examine and analyze samples. I introduce microfluidic tools and methods to accurately measure temperature and identify substances, or adulteration of substances, in small volumes. I accomplish this work through three projects. In the first project, a Microfluidic Thermometer, I demonstrate a simple and low-cost technique to accurately measure temperatures in small volumes using a 3D-printed microfluidic chip. With this method, the temperature of a sample can be measured with about a quarter of a degree Celsius uncertainty. For the second project, Chronoprints, I demonstrate a simple and low-cost method for identifying a sample based on visualizing how the sample changes in response to a perturbation over space and time. With this technique, authentic foodstuffs are distinguished from adulterated foodstuffs, adulterated medication is identified, and occasionally-confused pharmaceutical ingredients are easily distinguished. Finally for the third project, Enhanced Chronoprints, I demonstrate a simple and low-cost method for identifying a sample based on visualizing changes in the interaction of a falling metal bead with the sample. The cost, simplicity, versatility, and accuracy of these techniques make them valuable analytical tools in a variety of different fields and settings.