I have been neglecting this website for a while as I have been focusing on other tasks here at the University of Alberta.  New material will be coming relatively soon however, and possibly a more major overhaul.  The biggest professional news is that I have had several papers as author or co-author accepted over the past few months, and a very productive trip to Hilton Head 2010 presenting my work on producing gecko-inspired adhesives using commercial acrylic (Plexiglas, OPTIX etc.) molds.  This technology has been extremely productive for my research and it will be of great help to my graduate students who should be joining shortly, as we can now test a huge variety of structural materials for their long-term suitability in dry adhesive applications.  I have now completed a much more advanced adhesion test system in my lab that can quickly do automatically data collection that once took me hours before, and can achieve the microscale testing of anisotropic adhesion behaviors.  I had already accumulated a large backlog of microstructured adhesives to test prior to getting this system operational, so we are now investigating adhesion properties of dry adhesives produced with three orders of magnitude difference in Young’s modulus with various fiber geometries.  The fabrication technology for the dry adhesives is nearly fool-proof at this stage and we are actively looking for industrial partners to help commercialize the technology.

My latest published paper was published online on August 6, and is a review article for the journal Smart Materials and Structures, and it has been selected as a featured article by that journal.  That is now three papers I have been author or co-author on that have been selected as feature articles in different journals, so I am very happy and hope to continue the productive output.  The title of the paper is Recent advances in the fabrication and adhesion testing of biomimetic dry adhesives, and can be found here.

As part of my formal recruitment efforts I am adding links to important information for any potential graduate students who may wish to join my polymer micromachining research group at the University of Alberta.  The permanent links are listed in my potential students page, providing direct access to the Mechanical Engineering Departments deadlines, application requirement and general information.  Most applications will have to be started through this process, as opposed to contacting me directly.

The last few months have been very busy for me, and huge changes have been made personally and professionally.  I had to keep some of this information confidential until after everything was official but I can now publicly announce that I have taken at position at the University of Edmonton as an Assistant Professor in Mechanical Engineering.  This is close to a dream job for me as I have access to some of the best microfabrication facilities in Canada – the University of Alberta Nanofab and the National Institute of Nanotechnology.  Even better, I have lab space within NINT that is nearly perfect for setting up a research facility devoted to developing and characterizing polymer based processes, which have lower requirements for cleanliness and facilities than most silicon or inorganic materials processing.  I have just started at the university, and over the next few weeks should be getting ready for equipment and materials purchasing to get the polymer micromachining research lab operational.  The whole processes will likely take several months to a year, but there is a great amount of potential in the facilities and I am looking forward to making some unique contributions.

In the meantime, I have also gotten two other publications out – a paper in the Journal of Micromechanics and Microengineering authored by a student I co-supervised, and a conference article at ROBIO on the use of our directional dry adhesives as a potential foot for the climbing robot project.  One other conference and one Journal article have also been submitted on the topic of dry adhesives, with several others in preparation.

Because there will be a delay before I get my profile and full work website up and running, I figure I might as well put out the word that I am looking for students (Masters and PhD level).  There are university deadlines for when each student can apply (especially for international students) and I am working on determining those details.  I will post them here, as well as a link to my official university website when it is available.  Hopefully I will be a little more proactive from now on about managing this site and publicizing my work.

After a very long wait, I have finally got two new publications on the biomimetic dry adhesives published in the Journal of Micromechanics and Microengineering this month.  We submitted to this journal primarily because I was interested in demonstrating the fabrication technologies – specifically that we can make these adhesives with relatively low cost materials in reusable molds.  Since submission of these works, we have also got a conference paper accepted to ROBIO 2009 on how the directional dry adhesives might best be used for a climbing robot foot design, and have several more ready to submit by the end of this year.  Now that the fabrication papers are out, I can submit to different journals on the effects of different fiber geometries and materials on the performance of dry adhesives.

I have got a surprising amount of interest in the directional adhesive from multiple people and companies before the paper was published, so I think it is only fair to post a direct link to the publications now.  The non-directional paper is located here, and the directional paper is found here.  Since the directional one was submitted, I completed other tests on higher aspect ratio posts, and posts with bigger caps.  Our best adhesion comes from caps with relatively large overhangs in all directions but one – most similar to Figure 2a in the directional adhesion paper.  Testing these adhesives in orientations perpendicular to the direction of cap offset shows adhesion strengths of almost exactly the average of the maximum and minimum adhesion strength.  The results were basically expected, and indicate that the directionality is due to reducing overall adhesion strength by making it exceptionally weak in one orientation.  This weakness also extends to directional friction properties, as an adhesive sample sliding on a flat, smooth surface is far stronger in the direction of maximum peel strength than in the opposite orientation.  These behaviors are mostly covered in the upcoming ROBIO publication.

Our climbing robot design needs more control on the foot to appropriately load these adhesives, so it has to climb with the non-directional versions now in order to have any safety factor.  A future robot version with active feet however can use the directional adhesives with appropriate loading in order to lower its power consumption and vibrations during each step cycle because releasing the foot will require far less energy.  Now that the publications are out, I will be posting more images in the next few days showing some of the different fiber variations that we have produced so far.

It turns out that an interview that I did earlier this semester has got some attention via Slashdot.org.  It was great to have a second mention of my work on Slashdot – the first being part of my work with the original nanogram league at Robocup 2007.  It is a shame that the paper publication process takes so long, since I am still waiting to hear back on the journal submissions regarding the fabrication process for the optimized and directional adhesives, but hopefully as soon as those are confirmed, I can finally publish some of the more interesting images on this site.  One interesting theme in the Slashdot comments was the complaint about lack of actual commercial products using these dry adhesives – something I sympathize with.  Other companies and research groups are trying to commercialize these adhesives, but large scale manufacturing of structures with such small features has been extremely hard.  Even using my reusable mold techology, it still takes a couple hours to make each adhesive sheet.  Until the manufacturing methods are improved, I think these products will be in the high end applications first where costs are not a big deal, but sporting equipment, military applications and eventually adhesives for everyday use should all be possible.

It turns out that the directional adhesives I designed work quite well.  They stick great in one direction, but will fall off easily when pulled in the opposite way.  I submitted these results to a conference this week, but there is a very limited number of papers accepted at this late date, so I am all set for journal submission if it is rejected.  Once that happens, I can reveal more about the technique here.  The fabrication method for the directional adhesives is relatively simple, but it does turn out to require higher quality fabrication equipment than that presently available in our lab.  Thankfully, the newer cleanroom at SFU in 4D labs has what I require, and I just need to calibrate it further for more reliable results.

In other news, it turns out that the paper on microfluidics that we put out last fall was selected as one of the featured articles from 2008 in that particular journal.  That is two years in a row we have been able to get a featured article, so I am very happy that we were able to get something so worthwhile out in such a short period of time.  My new bonding method for the microfluidics should help us take it to the next level, with a complete process that has high yields.  I had been pushing from the beginning for appropriate bonding solutions, but between myself and Mona, we have come up with two process variations that should be extremely useful.  Hopefully, she and I will be able to get the quantitative data taken next week, and put out a technical note within a month or two.  Given how useful this general technology is for my dry adhesive work, I am really excited for the two projects to be coming together like this.

Every once in a while, I make a surprising breakthrough.  It definitely boosts the morale, but sometimes it also brings about new problems.  I have recently had success in both developing an anisotropic adhesive (different stickiness in different directions) and making a two level hierarchical adhesive  – making it far more adaptable and effective on different surfaces.  The big problem with the second breakthrough is that I am now exceeding the structural strength of the silicone adhesive, and the whole thing tears itself apart when I try to pull it off smooth surfaces.  Now I have to develop structural reinforcement for the silicone in order to actually have it survive multiple uses….  research always seems to have twists.

I have been keeping extraordinarily busy these past few months, but am trying to update on several topics that I have been working on.  Almost all my efforts this summer were devoted to the biomimetic dry adhesives project and the low-cost microfluidics.  Finally, both topics are being published – as a journal article for the microfluidics and as several conference and journal publications for the adhesives.  The primary focus for me is enhancing the yield of the adhesives through process tweaking, but I have gotten to the point now where the geometry of all posts can be easily modified so I am working on optimizing the geometry for maximum adhesion.  We are actually starting to integrate these adhesives with a climbing robot, but so far, the robot isn’t quite strong enough to detach after the adhesives stick to a smooth surface.  Hopefully the next generation of adhesives will show aniostropic behavior with different loads, and avoid this problem in the future.  Other breakthroughs have included my development of a simple collimation method for use with our deep UV patterning of PMMA, which allows our features to be defined in aspect ratios above 6:1 instead of the approximately 1:1 which had been a limitation in our earlier work.  Keep posted for future developments and applications, there should be a lot of interesting results coming soon.

I am starting to update some of the images to go along with different project descriptions. Updates on both the self-assembly page and the dry adhesive page include more images now. The good pictures will have to wait until later publication, but hopefully there will be many more image updates in the next few weeks after I get more SEM images of the dry adhesives and the microfluidics.

I just got back from Hilton Head last night and am still trying to get adjusted to the time change. The conference was great, with a lot of new interesting projects demonstrated by a number of different groups. I met some fantastic people in the MEMS community, and got updated on a lot of new developments in the field. The only thing bad with the trip is that I have maintained my near perfect record of having a flight canceled or changed on me while traveling to a conference. I am back one day later than I was expecting and with damaged luggage, but at least nothing was lost this time. Someday I will get to and from one of these meetings without difficulty, but it hasn’t happened yet.