Electrowetting On Dielectric (EWOD) Digital Microfluidics For Electronic Hotspot Cooling
Bindiganavale, Govindraj Shreyas
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Electronics cooling was a field dominated by bulky and heavy heat sinks, heat pipes and fans for decades. Lately, the size of the electronic components has decreased to a substantial extent with an increase in performance. This has fuelled a need for smaller, lighter, yet efficient cooling systems. A lot of research has been done to build innovative cooling solutions which satisfied most of the requirements as stated above. Some of them still have limitations like use of the right coolants and design challenges. Digital microfluidics is one field which can solve all these issues by providing a simple, reliable and efficient way of pumping coolants over hotspots. For this purpose, a microfluidic hotspot cooling device was fabricated which used special liquids called Ionic Liquids (IL's) as coolants. Unlike other coolants used, IL's has the property of being thermally stable at elevated temperatures and chemically inert to most of the known metals. This thesis report describes the performance of IL's in the device for hotspot cooling. Liquid Crystal Thermographical analysis was performed in order to estimate the temperatures of the hotspot and heat removal rate calculations were performed based on the analysis. In order to check the quality of the results, a comparison was made with the results of DI water. It was observed that DI water emerged as the best liquid for hotspot cooling and IL's performed poorly. This was due to the high heat capacities and thermal conductivities of water. In order to get better results for IL's, it was concluded that the thermal conductivity values should emulate that of water's values. Adding CNT's (Carbon Nanotubes) to the IL can help us in this regard. Moreover, as the heat removal rate was a rough calculation, it was hard to estimate an accurate rate for the DI water and IL. Efforts are being made to come up with a realistic approach towards estimation of this data.In future, by increasing the thermal conductivities of IL's and using advanced methods to perform the analysis with an improvement in design of the hotspot cooling device, cooling hotspots in small, compact and powerful electronic devices can become a reality.