Heat is an unavoidable byproduct of the normal operation of an electronic device, generated as a result of electrical energy being converted to thermal energy during circuit activities. As the need for fast electronic devices increases, the ability to safely dissipate large amounts of heat from very small areas is key to many of today's cutting edge technologies. To this end, cooling of electronic systems (such as computers, lasers, radars, etc) is becoming a major challenge in the design of next generation of such devices.
The proposed investigation will explore the active and on-demand micro actuation and transport of liquid droplets, a process dubbed Digitized Heat Transfer (DHT), for effective thermal management of high power compact systems. In DHT, individual droplets are discretely manipulated. This enables the basic operation in any fluidic device (transporting, mixing, and analyzing) to be performed in simple instructions without the need for moving mechanical parts.
In this investigation, the transport of coolant is achieved by modification of surface tension forces on a droplet interface by application of electric forces. Surface tension is a dominant force for liquid handling and actuation at micro scales. The proposed technique is based on three observations: (i) by using metals/alloys that are liquid at room temperature (instead of e.g. water or air) the heat transfer rate of a cooling system can be enhanced significantly, (ii) moving droplets are dominated by an internal recirculation (missing in continuous flows) that will enhance mixing and consequently heat transfer; (iii) electric actuation of a droplet interface is an efficient, low power, and low voltage actuation technique for manipulating liquids at micro scales.
Various electric actuation methods will be investigated by computational and theoretical means. DHT will be studied at a fundamental level by identifying the relevant parameters and non-dimensional numbers, and by determining the heat transfer rate for a periodic array of conductive and dielectric droplets of various sizes. It is expected that digitized electrohydrodynamics will offer a viable cooling strategy to achieve the most important objectives of electronic cooling, i.e. minimization of the maximum substrate temperature, reduction of the substrate temperature gradient, and removal of substrate hot spots.
In addition to the technical advances in thermal sciences, fluid dynamics, and computational techniques anticipated above, this project provides an application focus that will be of interest to researchers and students working in electrical, chemical, mechanical, and aerospace engineering, as well as physicists, biologists, and medical scientists. Undergraduate research assistants will be sought via supplementary REU support, and can be expected to come from the previously mentioned fields. The PI intends to develop a course in micro scale convective transport and expand his current course on micro and nano fluidics with the addition of both a fabrication and a computational component. The PI's existing multidisciplinary courses will be enriched with results from this work, expanding student exposure to different aspects of micro fluidics. Because of the multidisciplinary aspect of this subject, wide student interest is expected. Storytelling will be reinstated in the classroom as a method of not only science education but also ethics education, history, and community values. A Lilliput Summer Camp is also proposed, enabling local secondary school students to participate in a weeklong educational experience with an emphasis micro scale phenomena.
