Localized Microwave Heating in Microwells for the Use as Microreactors in Mobile Lab-on-a-Chip Developments

We report the application of an open-ended semirigid coaxial cable as a miniaturized microwave heating source in microwells made of Poly(methyl methacrylate) (PMMA) and Polydimethylsiloxane (PDMS) for the realization of a microreactor for mobile lab-on-a-chip devices. By using standard power RF-components, originally developed for mobile wireless communication applications, microwave fields with an incident power up to 2.5 Watt and with frequencies in the range between 1 and 7 GHz were applied to microliter sample volumes. Microwave fields coupled into the fluid by the open end of the miniature coaxial cable lead to localized dielectric and, to a minor degree, also resistive heating of the fluid which induces continuous flow conditions with high mass transport and an associated temperature field with high temperature gradients in the microreactor. Fluid dynamic simulations support and illustrate the experimental findings.