A new contender: the horned frog or horny toad or horned toad...

Over the last week, I have mostly been focusing on further research of heat pipe technology and have been attempting (with difficulty) to quantify the potential action that could result in using lizard inspired micro structured surfaces in a passive heat pipe cooler. I have again read an interesting paper on the anatomy of the Thorny Devil and discovered that I had overlooked some other lizards with interesting features that promote water harvesting.

 

Enter the Phrynosoma cornutum!

Texas Horned lizard (image credit)

Initially in my previous Nanotechnology project, I had reviewed the strategy database on AskNature.org and came across the Thorny Devil. I found an interesting paper entitled 'Moisture harvesting and water transport through specialized micro-structures on the integument of lizards'. It has many interesting images and observations of different lizards including the 'Phrynosoma cornutum' which is also known as the Texas Horned lizard and is a member of the "horned frog" family. Supposedly they have a similar rounded body and blunt snout as some frogs. The research paper shows that this horned lizard shows further enhancement of the undercut micro structure and the image shown below (skin cross section) is actually more pronounced than that of the Thorny Devil. With that, it turns out that the Thorny Devil lizard is not in the same family as the Horned lizard and although they show similarities in their structure, they are supposedly an example of convergent evolution where two different species have evolved similar anatomies to achieve the same endpoint e.g. eating lots of ants. To protect themselves, these lizards will put their head between their front legs and a part of their neck will then resemble a false head with horns, scaring or poking predators if they come too close. It just shows again that there are many various strategies in nature, even within specie groups and families. Having a holistic overview is difficult to achieve. 

Section of Texas Horned devil (image credit)

 
Whether the Thorny Devil is in fact a lesser opponent for design inspiration will depend on whether semi circular channels inspired by the Texas Horned lizard will improve capillary action under the stringent conditions necessary in heat pipe containers. The addition of this design feature (the undercut channels) would seem like a logical iteration from the simplified hexagonal posts fabricated in previous concept work. The next post will hopefully show some quantitative estimations of the capillary action due to this geometry in a passive heat pipe setup.

Can't see the wood for the trees

Yesterday I had my first 'milestone' presentation with my supervisor, Torben Lenau. As part of the problem statement, it was necessary to set out a time line of activities which included milestone presentations where reached goals are presented, discussions are had, changes are made and the supervisor can keep up with my activities. It can also mean that the direction of the thesis can change...

Micro cooling electronics

CPU pre-cooler install (image credit)

I have been researching micro cooling technologies used in electronics, specifically CPU (computational processing unit) devices. Newer devices are getting smaller and more powerful but the draw back is that they are giving out more heat. Heat flux is the rate of heat energy transfer through a surface and used as a measure of CPU performance. A CPU such as a Pentium 4 processor (used in home PCs and laptops) can emit heats of up to 115 W/cm² (where W is Watts or Joules per second). There are devices producing up to 150 W/cm² in computers and in other applications (hybrid cars, defence systems) researchers are looking at heat fluxes of up to 1000 W/cm²! Researchers like Issam Mudawar at Purdue university and Meilin Liu at Georgia Intitute of Technology (and many others) have been trying to solve the problem of over heating electronics in domestic, industrial, aviation and space systems.

Over the last 5 weeks, I have come to realise that the issue of cooling electronics is a huge area. There are a number of different techniques used including heat sinks (passive and fan assisted), liquid cooling, refrigeration, thermoelectric cooling, single and two phase changing liquids (using latent heat effects) and all of these are huge subjects in themselves. Many research papers have been written regarding the optimisation of geometries, fluid flow models, heat transfer and thermodynamics. Some observers believe it is now time to implement innovative and novel solutions which can solve the problem rather than focusing on theory, which can be time consuming in a world where technology is moving at such a fast pace. I felt that by applying some biomimetic inspired elements to a certain cooling process, there might be some benefits. This was a wrong approach.

Focus

Silicon wafer with lizard inspired geometry

The reason I wanted to write a thesis on 'Thorny Devil lizard inspired cooling' was to implement my previous findings in a cooling solution principal. At the milestone, my supervisor reminded me of this. Although my research was interesting and worthwhile for a holistic overview of micro cooling technology, it was taking on too much. It was necessary to focus on the interesting capillary action that takes place on this lizard inspired surface and how this passive action could be used in a cooling solution. It does not have to be limited to CPU cooling but a concept needs to be proven to work. For our next meeting (Tuesday 30 April), my tasks are to quantify:

1. How to use capillary action to increase surface area (and promote heat transfer) and guide fluid around a system to improve cooling.
2. How much heat are we talking about and how efficient a system like this could be.

It's on!

Some admin stuff...

I don't know this man - Image credit

On Friday April 5, I received an email saying that I have been officially registered in the DTU system for my thesis project. Not only that, I have been registered 1 month behind so the official date is actually March 1! I will be taking 32.5 ECTS so that means my thesis 'contract' deadline is Thursday August 15 2013. It was necessary to write out a problem statement outlying what I wanted to achieve, my learning objectives and a time line. According to friends, the problem statement can change up to a month after submission but for now the title is 'Thorny Devil lizard inspired cooling' and my supervisor is Prof. Torben Lenau.

The problem statement can be found here. It was tricky writing out the problem statement in order to get the scope correct, especially this early in the project. Defining the learning objectives needed wording like 'After the project the student is capable of …' so that the examiner can judge whether I have learned anything. My supervisor provided some useful information on how to complete a problem statement: Learning Objectives for Master's thesis at DTU Management Engineering. It was also advised to relate the statement to the competences listed in my MSc description.   

 

Hello from Copenhagen

Welcome to my MSc blog. This is my 4th and final semester at the Technical University of Denmark where I have been studying as a masters student in engineering design and applied mechanics. Over the next 5-6 months I will be researching, conceptualising, analysing and hopefully creating a new micro cooler device for the cooling of electronics. 

Thorny Devil lizard (image credit)

This blog is a follow up to my previous one that I kept last semester and followed an interesting 3 week course that I was doing on the creation of a micro surface inspired by the Thorny Devil lizard. If you wish to review the blog, you can find it here.

I learned a lot from that blog, mainly that I should never keep one again! It was very time consuming but I think it is a nice way to keep things together; my thoughts, concepts, interesting finds and perhaps, who knows, someone might find it interesting. This time, however, I will try to keep it more structured and to the point (less waffle, as I am inclined to do), with at least an entry per week summarising my work done. Apart from focusing on the main content and activities of the thesis, I will also describe any organisational activities or bureaucratic issues which have influenced progress. Hopefully, this blog will act as some sort of guide for future students (on how not to do things perhaps!). Ultimately, I want to expand my knowledge on the interesting issue of cooling micro electronics and bring some new thoughts and insights to the world.

Thank you,
Bryan.
www.suiledesign.com