We present a technique to induce temperature gradients in flexible microfluidic devices with microwave energy. Microwave power decays exponentially in the propagating medium, and the rate of decay is higher for water compared to polymers or glass due to its high dielectric loss at microwave frequencies. We have metal electrodes on chip that are integrated with microchannel to delivery microwave power to fluid at a variety of frequencies. The temperature change of fluid is measured by observing the temperature dependent fluorescence intensity of Rhodamine B dye. Our method produces linear as well as nonlinear temperature gradients within microchannels. The nonlinear sinusoidal shape gradients along 7-mm distance with temperature as large as 53 °C and as low as 31 °C and linear temperature gradient along 2-mm distance with a slope of 7.3 °C/mm were established within 1 sec time period. Many biological and chemical applications requiring rapid temperature gradients have the potential to benefit from this new technique.
Citation: Lab on A Chip
Pub Type: Journals
Temperature, Microfluidic channel, Fluorescence, Rhodamine, Microwave, Gradient