Get it done! Concept fab, experiments and thesis plan

Wow...10 weeks until thesis hand in...how did that happen?! I was a little distracted last week as we had a very exciting folk music night at the apartment which went down very well. But since then, I have been trying to move things forward and can report some progress.

Wick patterns on silicon wafer surface

Creating the concepts

I have sent an update on my thesis progress to Rafael Taboryski and Simon Tylsgaard Larsen at POLYMIC. During my previous work with them, we fabricated some micro structures on silicon wafers using photolithography and etching equipment at the Danchip National Center for Micro- and Nanofabrication clean rooms. The idea was to test how these structures (inspired by the skin of a lizard) could be scaled and how this scaling affected the hydrophilic and capillary action characteristics of the surface. Some qualitative rate of rise tests were carried out but due to time constraints it was not possible to show how varying channel width could improve these properties.

Cut SI patterns before anode bonding

In my proposed plan, I have tried to simplify the method for producing flat micro heat pipes that could be fabricated on the remaining SI wafers which have been prepared for etching. I just hope they have not been discarded! There are 4 wafers left so by etching these with different pattern characteristics (varying etch depth, channel width, surface treatments perhaps), variations of wick patterns could be produced. By cutting these patterns out, 2 of the same design could be bonded together using an anode bonding process to create a heat pipe container. Then the container would need to be filled with the working fluid (DI water) and sealed so that any other gases are removed. If 4 wafers were etched, it might be possible to create 12 different heat pipe containers with varying wicks. However, all of this work will depend on whether Rafael and Simon have time to assist and Danchip facilities are accessible over the coming weeks.

Hot plates with control box on right

Experimental testing

To get things moving with the experimentation stage, I decided to contact Giuliano Bissacco at the MEK department at DTU to discuss heating equipment for use in testing of the flat micro heat pipes. He has worked with cooling problems before and was very helpful in our meeting today. He showed me a hot plate/thermal test rig which could be used for testing. An aluminium support (good conductor of heat) might be needed to hold the heat pipe containers where the surface area is chosen such that a controllable heat flux (watt per area) can be applied to the evaporator end of the heat pipe. However, we discussed using the plates themselves to grip the heat pipe container gently and a piece of insulating material (e.g. Rockwool) could be placed on the top side to ensure that most of the heat input comes from the bottom plate (as in microprocessor setups).  

Thesis structure

Finally, I have put together a visual overview of the report structure. You can find the presentation here which shows an overview of the different elements that I will try to cover: objectives, report layout and milestones as per the problem statement. I am considering using LaTex but just need to get off my ass and get going with it!

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