Thermal droplet microfluidics: From biology to cooling technology

Droplet microfluidic platforms have been developed to produce mono-dispersed microdroplets and provided substanial progress in many chemical, biological, and biomedical applications. Droplets generated in microfluidics can perform multiple functions by either changing the reaction conditions within each droplet or doing the same reactions in parallel, series, or combinations. These reactions mostly require precise control of droplet temperature using contact or non-contact heating sources, including optical-, electrical-, mechanical-and acoustic-based heating techniques. This work exclusively presents thermal energy sources in microfluidics and provides insights into the physical interpretation of thermal actuation of microdroplets. It then highlights advances in thermal droplet microfluidics for biomedical, chemical and engineering applications. The biomedical applications include biosensing, drug discovery, drug testing, and antibiotic susceptibility testing. The chemical applications include synthesis of microgel droplets and Janus particles. The engineering applications include an overview of thermal manipulation of the generated droplets and employing emulsified droplets in thermal management and cooling applications. This review supports the development of new methods to meet different demands arising from these applications. Finally, the challenges involved in the widespread use of thermal microdevices are discussed and further considerations for prospective research in this area are highlighted. ? 2021 Elsevier B.V. All rights reserved.