Seven or Never: On-Off Adhesives Make Progress Towards Commercial Applications

Sometimes the biggest inspiration for technological development is nature. Biomimicry—as it is known—is leading to advancements in wind power where the small bumps on the leading edges of the fins of humpback whales are duplicated on the blades of wind turbines.  Another example of this biomimicry is the tiny hairs on the petals of the lotus flower that repel water being mimicked in the waterproof coatings for mobile phones.

In the field of nanotechnology and biomimicry there has been one creature of nature that has been of particular interest: The gecko. Researchers have been fascinated with the gecko’s gravity-defying ability to walk on ceilings and not fall. The gecko’s exploits are accomplished by hundreds of thousands of tiny hairs, called setae, covering their feet. Each one of these setae itself has nanoscale projections, which are so small that they produce the weak molecular interactions known as van der Waals between themselves and the substrate.

Over three years ago, I covered research coming out of the University of California Santa Barbara (UCSB) that was exploiting the gecko’s design to potentially produce industrial adhesives that could be actuated—or turned on and off, like a switch—by magnetism.  I joked at the time that it could enable Spiderman-like super powers. But I also suggested that this was a technology that was commercially attractive.

With this commercial opportunity suggested by none other than myself, I thought I should investigate how far along the technology had developed as part of the ongoing series: “Seven or Never,” which looks back at technologies I have covered over the years to check on the current state of development.

Professor Kimberly L. Turner, who has been leading this research for the last decade at UCSB, gave me the update.

“We began working on this research in about 2003,” Turner told me via email. “My student at the time, Michael Northen, got interested in synthetic adhesives, and we were the first group to really focus on the hierarchical nature of the problem by using active MEMS technology.  We were able to integrate meso-, micro-, and nano- scales into an active device that could be changed from an adhesive state to a non-adhesive state.  Later on, we were able to use magnetic actuation to 'release' the adhesives from a stuck state.  It was a very exciting time.  That was back in 2006.  The work has grown in many directions since that early work.”

In addition to Northen, Turner has worked with three other PhD candidates in this area, including Abhishek Srivastava, Sathya Chary, and John Tamelier.

The work of Tamelier has been aimed at scaling up the adhesive patches that the team has been developing. He is also designing and building a test mechanism to study the best ways to approach surfaces with the adhesives in order to maximize adhesion.

“John Tamelier is about to have a paper come out in Langmuir which focuses on that work,” said Turner. “This is an essential result for achieving high adhesion with micro-robots.  How the foot of the robot approaches the surface it is running on is key to how much adhesion is generated.  The adhesives we are using for this are passive adhesives, meaning that they work without actuation.  However, they are anisotropic, meaning if moved in one direction they are sticky, but in another they are not sticky, thus creating more flexibility and ease in removal.”

Turner is quick to mention that the work in active devices (those that can be actuated to turn on or off) that were mentioned in my initial blog post covering their technology has continued.

“In a collaboration with the Army Research Lab and a local MEMS foundry, IMT Inc., we integrated thermal actuators and piezoelectric actuators into the adhesives,” explained Turner in an e-mail. “We were able to show that by adding force (from the thermal actuators) in the direction perpendicular to the pull-off direction, we could enhance the adhesion.  This was a very challenging fabrication, and was limited as to how much surface area we could generate, but it is a promising result.”

The aim of the “Seven or Never” series is to find out how far along a hopeful technology gets over a period of time. While I first covered the technology just three years ago, the first successful results were achieved back in 2006—right in line with our seven-year time frame. But as we learned from our first installment of this series, seven years is hardly enough time to bring an emerging technology to market and this one appears to be no exception. Nonetheless, the researchers are pursuing real-world, commercial applications.

“We do hold a patent on the magnetic technology, and have had quite a lot of interest from industry on commercializing,” said Turner.  “We have not been focused on that as of late, as it was not quite to the stage where it is useful for many of the applications of interest, but it is close.  We are excited about the future of this technology.”

With efforts being made in commercializing their technology, I asked Turner what her thoughts were on the challenges facing innovation and bringing an emerging technology to market.

“Easier industrial partnerships would certainly make this a lot smoother,” said Turner. “ There always seems to be a problem with intellectual property agreements, and this takes a lot of time and effort to iron out.  If there was an easier way to get this done, I think more industry would partner with universities, and it would lead to faster innovation.”

Despite these challenges, Turner added: “I bet there will be some products in the next 5 years…the possibilities are vast.”

Photo: Canebisca/iStockphoto

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Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

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