Papers Published

1. Paik, P; Pamula, VK; Chakrabarty, K, Thermal effects on droplet transport in digitial microfluidics with applications to chip cooling, Thermomechanical Phenomena in Electronic Systems Proceedings of the Intersociety Conference, vol. 1 (September, 2004), pp. 649-654 .
   (last updated on 2022/12/30)

   Abstract:
   Thermal management has emerged as a critical issue in the design of integrated circuits (ICs). As feature sizes decrease and package densities increase, current package-level cooling techniques will soon become inadequate. While a number of MEMS-based cooling solutions have been proposed to address cooling at the IC level, many are not equipped to address the problem of real-time active and "smart" cooling, where hotter thermal regions (i.e., hot areas) are detected and subsequently cooled at an increased rate. We describe an alternative cooling method, on a platform we call "digital microfluidics," where nanoliter-sized discrete liquid droplets immersed in oil are manipulated. Cooling droplets are actuated independently in user-defined patterns over an array of electrodes by electrowetting, eliminating the need for external pumps. This paper presents the effects of temperature-dependent system parameters on droplet transport in this digital microfluidic platform. We demonstrate experimentally that under a fixed frequency, the minimum voltage required to oscillate a microliter-sized droplet across a linear electrode array decreases as much as 30% for a 50°C temperature increase. The effect of two temperature-dependent parameters, interfacial tension and oil viscosity, are investigated as possible mechanisms. The results presented here suggest that digital microfluidics is an attractive platform for smart, active cooling.