An Infrared System for Measuring Temperature Distribution in Microfluidic Devices

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Droplet microfluidics (DMF) is an enabling technology for high throughput screening analysis (HTS) demanded by many applications such as life science research, drug discovery, and material synthesis. DMF employs nanoliter-sized drops that can be generated at kHz rates in microchannel networks by injecting one fluid into another immiscible fluid (i.e. water into oil) as mobilized reactors for HTS applications. Because they have a small volume and three-dimensional flow, these droplets allow for fast mixing, enhanced reaction kinetics, and reduced reagent consumption and analysis time. One of the key functions that allow DMF to serve as an enabling technology for HTS is heating of individual droplets; many applications, such as DNA amplification via polymerase chain reaction, thermally initiated polymerization and click chemistry, rely on temperature change. Localized heating within droplets can also be utilized to enhance mixing of reagents. The applicant’s current research program focuses on DMF with a particular emphasis on developing microwave technologies for sensing and heating of individual droplets. Her team has demonstrated that microwave is capable of generating localized heating within individual droplets and increasing their temperature by 42 degrees within 15 ms, which has tremendous potential to expand the scope of applications of DMF, for example, for manufacturing polymeric beads, DNA sensing, click chemistry, and the pharmaceutical industry. To fully realize this potential requires a technique for accurate, inexpensive, and non-intrusive temperature measurement; this will be enabled by the requested Infrared (IR) Imaging system. IR imaging allows the temperature of droplets in a microfluidic chip to be retrieved by simply capturing surface images of the chip, which is non-intrusive to droplets, easy to operate, and eliminates the need to use temperature-sensitive fluorescent dyes as temperature indicators. Its high speed imaging (1000 frames per second at full resolution) matches the droplet transport speed, allowing the transient information to be obtained. Its high resolution (of as small as 3um) is well suited for DMF as most droplets have lengths of tens to hundreds of microns. This easy-to-operate imaging system will allow the characterization of microwave heating for DMF, opening up a new range of applications such as click chemistry, DNA amplification and sensing using heating-assisted mechanisms, and manufacturing polymeric beads for drug delivery. The integration of these areas enabled by this equipment will foster a multidisciplinary environment for training HQP in the field of microfluidics, microwave, microfabrication and in particular temperature measurements using IR imaging techniques.