Digitized Heat Transfer: A New Paradigm for Thermal Management of Compact Micro Systems

热是电子设备正常工作时不可避免的副产品，是电路活动过程中电能转化为热能的结果。随着对快速电子设备需求的增加，从非常小的区域安全地散发大量热量的能力是当今许多尖端技术的关键。为此，电子系统（如计算机、激光器、雷达等）的冷却正在成为下一代此类设备设计中的主要挑战。该研究将探索液滴的主动和按需微驱动和传输，这一过程被称为数字化传热（DHT），用于高功率紧凑型系统的有效热管理。在DHT中，单个液滴被离散地操纵。这使得任何流体装置（运输，混合和分析）的基本操作都可以在简单的指令中执行，而无需移动机械部件。在这项研究中，冷却剂的输送是通过施加电场来改变液滴界面上的表面张力来实现的。表面张力是液体处理和微尺度驱动的主导力量。所提出的技术基于三个观察：(i)通过使用在室温下为液体的金属/合金（而不是例如水或空气），冷却系统的传热速率可以显着提高；（ii）移动的液滴由内部再循环主导（在连续流动中缺失），这将增强混合和因此的传热；液滴界面的电动驱动是一种高效、低功耗和低电压的驱动技术，用于在微观尺度上操纵液体。各种电动驱动方法将通过计算和理论手段进行研究。DHT将在基础水平上进行研究，通过确定相关参数和非量纲数字，并通过确定各种尺寸的导电和介电液滴的周期性阵列的传热速率。预计数字化电流体动力学将提供一种可行的冷却策略，以实现电子冷却的最重要目标，即最小化衬底最高温度，降低衬底温度梯度，去除衬底热点。除了上述预期的热科学、流体动力学和计算技术方面的技术进步外，该项目还提供了一个应用重点，将引起电气、化学、机械和航空航天工程领域的研究人员和学生以及物理学家、生物学家和医学科学家的兴趣。本科研究助理将通过REU的补充支持寻求，并且可能来自上述领域。PI打算开设一门关于微尺度对流传输的课程，并通过增加制造和计算组件来扩展他目前的微纳米流体课程。PI现有的多学科课程将因这项工作的结果而丰富，扩大学生接触微流体学的不同方面。由于这门学科的多学科性，预计会引起广大学生的兴趣。讲故事不仅是科学教育的一种方式，也是伦理教育、历史教育、社会价值教育的一种方式。利力浦特夏令营也被提议，让当地中学生参与为期一周的教育体验，强调微观尺度的现象。

CBET-0756505, MohseniHeat 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.