Geckskin, a UMass-born Technology, Inspires Innovative Applications from the Home to Outer Space
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Geckskin, an adhesive technology developed by researchers at UMass Amherst, has made a name for itself in a number of fields. Named one of the top five science breakthroughs of 2012 by CNN Money (now CNN Business), it is so powerful that an index-card sized piece can hold 700 pounds on a smooth surface, such as glass, yet can be easily released, and leaves no residue.
Geckskin offers tantalizing possibilities for synthetic devices that can easily attach and detach everyday objects such as televisions or computers to walls, as well as medical, industrial, clothing, and home applications.
Inspired by Geckos
The ability of geckos to climb vertical and overhanging walls has long fascinated scientists and laypeople alike. Geckos possess a complex set of specializations for adhering to smooth surfaces, which include stiff tendons that insert into their toepads. On their toepads, geckos possess millions of minute hairs called setae that act as a soft substrate that can conform to surfaces. Scientists have studied geckos for decades but the principles underlying gecko adhesion remained elusive until now.
At different locations on the campus of UMass Amherst, two scientists were independently analyzing gecko adhesion with different aims. Biologist Duncan Irschick had been studying gecko climbing and clinging adhesion for over 20 years. Polymer scientist Alfred Crosby had been working on polymer adhesion for almost as long and was interested in creating a novel adhesive material that would embody gecko attributes.
In 2009, with a grant from DARPA, an agency of the U.S. Department of Defense, Crosby's research team was working on synthetic adhesives built on a simple yet revolutionary principle: They believed that if adhesives were made with stiff fabrics, adhesive force could increase dramatically. Most commercial adhesives are soft and gooey, yet the Crosby group believed that this compliant nature was a limitation.
The Geckskin Team
Curious if their ideas about stiffness were upheld in geckos, the Crosby team reached out to Duncan J. Irschick. Working together, they discovered, as hypothesized, that geckos possessed stiff tendons attached to their toepads, which acted much like the stiff fabric adhesives that the Crosby lab had been developing.
Geckskin was formally revealed to the world in February of 2012, with the publication of an article in the journal Advanced Materials. Crosby, Irschick, doctoral candidate Mike Bartlett, and the rest of the research team had unlocked the simple yet elegant gecko secret for adhesion and created a novel technology that is revolutionizing how we attach objects together.
Al Crosby is a materials scientist and engineer interested in the mechanics of soft materials and biological systems and the leader of the initial project that developed Geckskin. In addition to Geckskin, he leads a research group focused on learning and using lessons from nature to influence structure-property-function relationships in synthetic materials. His research on adhesion, wrinkling, cavitation, and nanoparticle assemblies has garnered international acclaim and numerous honors and awards. He has published more than 180 papers and has delivered well over 200 invited, keynote, and plenary lectures at universities, conferences, and companies worldwide. His research has been highlighted extensively in the popular media and he holds several patents for the technologies that have evolved from his group's focus on fundamental science and engineering.
Duncan J. Irschick is an integrative biologist and innovator interested in the evolution and ecology of animal athletics and how biological form can inform synthetic design. His research on gecko adhesion, animal movement, and biomimicry has garnered international acclaim and many honors and awards. His early research on geckos first revealed the adhesive force of gecko toepads, which set a standard for biologists creating synthetic gecko adhesives. Irschick has published more than 175 papers and has been invited to give more than 90 talks at universities all over the world. In 2012 he gave a TEDx talk at the Sorbonne in Paris as part of a conference entitled The New Age of Enlightenment. He is also a Fulbright Specialist and has given plenary talks to various universities.
Mike Bartlett is an inventor of Geckskin and is the first author on the seminal Geckskin paper that appeared in the February 2012 issue of Advanced Materials that introduced Geckskin to the world. He published several papers in high impact journals on the science behind Geckskin and won several awards for his research. He now leads a research group as a faculty member at Virginia Tech University.
Daniel R. King was an inventor of Geckskin. Dan was a coauthor on the seminal Geckskin paper that appeared in the February 2012 issue of Advanced Materials, as well as the lead author on several additional publications regarding Geckskin. He received several awards and much recognition for his research accomplishments on Geckskin, and he went on to be an Assistant Professor at Hokkaido University in Japan.
Michael Imburgia was a PhD student researcher examining the role of compliance in both geckos and in synthetic devices and how it influences adhesion on different surfaces.
Andrew Croll is an inventor of Geckskin and was instrumental in developing the guiding scaling theory behind the design of Geckskin. He was a coauthor on the seminal Geckskin paper that appeared in the February 2012 issue of Advanced Materials. Andrew is a Professor of Physics at North Dakota State University.
Beth Paret was an undergraduate majoring in art history, and was instrumental in applying her sewing skills to integrate different elements of Geckskin, which was crucial for developing the first usable prototypes. She also provided invaluable graphic design skills to illustrate the skin-tendon-bone connections that were a critical finding in the seminal Geckskin paper that appeared in the February 2012 issue of Advanced Materials.
The Science
Unlike traditional pressure-sensitive adhesives, which rely on viscoelasticity for adhering to surfaces, Geckskin relies on a concept known as draping adhesion. Draping adhesion is created with materials that can drape to create conformal contact with a surface while still maintaining high, elastic stiffness in directions where forces will be applied. This design enables adhesive loads to be more evenly distributed across the pad surface, while also allowing for a rapid and low-energy transition between attachment and detachment.
The Geckskin technology does not rely upon specific materials compositions; however, in many of the devices developed initially in the Crosby labs, they were composed of stiff fabrics—such as carbon fiber or Kevlar—with soft elastomers, such as polyurethane or polydimethylsiloxane (PDMS). The key innovation of Geckskin was the integration of a soft elastomer (the pad) with a stiff fabric (the skin), allowing the pad to drape over a surface to maximize contact. Further, as in natural gecko feet, the skin is woven into a synthetic tendon, yielding a design that plays a key role in maintaining stiffness and rotational freedom. The end result is an adhesive device that is powerful, easily removed, and leaves no residue.
Geckskin Products
Geckskin technology has been used for a number of commercial applications. One example is Frost King’s Reusable-Adjustable Geckskin Technology Weatherseal, which is an adhesive that “allows you to get an exact fit and placement every time you place on a door or window.”
Current Projects
Current efforts building upon the foundations of the Geckskin technology are focused on developing reversible adhesives for extreme environments, robotics, and for enabling a more sustainable planet. Extreme environments include the space environment, where large fluctuations in temperature, radiation, and ultra-low vacuum present unique challenges for soft elastomer composites. Crosby, along with a team of postdoctoral and student researchers, are using the guiding Geckskin principles to overcome these challenges in a systematic manner. Current projects are funded by federal agencies and industrial sponsors.
Resources
Books
- Mimic Makers: Biomimicry Inventors Inspired by Nature by Kristen Nordstrom. ISBN: 9781580899475. Image credit: Penguin Random House.
- Wild Inventions: Ideas Inspired by Animals by Sandra Markle. ISBN: 1728467950. Image credit: Lerner Publishing Group.
- From Gecko Feet to Adhesive Tape by Wil Mara. ISBN: 9781624317521. Image credit: Cherry Lake Publishing Group.
- Biomimicry Handbook by Ashley Chase. ISBN: 1945192119.
Publications
- Bartlett MD, Croll AB, King DR, Paret BM, Irschick DJ, Crosby AJ. Looking Beyond Fibrillar Features to Scale Gecko-Like Adhesion. Advanced Materials. 2012; 24(8):1078-1083: DOI: 10.1002/adma.201104191.
- Bartlett MD, Croll AB, Crosby AJ. Designing Bio-Inspired Adhesives for Shear Loading: From Simple Structures to Complex Patterns. Advanced Functional Materials. 2012; 22(23):4985–4992. DOI: 10.1002/adfm.201201344.
- Pendergraph, SA, Bartlett MD, Carter KR, Crosby AJ. Opportunities with fabric composites as unique flexible substrates. ACS Applied Materials and Interfaces. 2012; 4(12):6640–5. DOI: 10.1021/am3017812.
- Bartlett MD, Crosby AJ. Scaling normal adhesion force capacity with a generalized parameter. Langmuir. 2013; 29(35):11022–7. DOI: 10.1021/la4013526.
- Bartlett MD, Crosby AJ. High Capacity, Easy Release Adhesives From Renewable Materials. Advanced Materials 2014; 26(21):3405-3409. DOI: 10.1002/adma.201305593.
- King DR, Bartlett MD, Gilman CA, Irschick DJ, Crosby AJ. Creating Gecko-Like Adhesives for ‘Real World’ Surfaces. Advanced Materials 2014; 26(25):4345-4351. DOI: 10.1002/adma.201306259.
- Pendergraph SA, Bartlett MD, Carter KR, Crosby AJ. Enhancing Adhesion of Elastomeric Composites through Facile Patterning of Surface Discontinuities. ACS Applied Materials and Interfaces. 2014; 6(9): 6845-6850. DOI: 10.1021/am5006546.
- Bartlett MD, Crosby AJ. Material Transfer Controlled by Elastomeric Layer Thickness. Materials Horizons. 2014; 1(5): 507-512. DOI: 10.1039/c4mh00106k.
- Gilman CA, Imburgia MJ, Bartlett MD, King DR, Crosby AJ, Irschick DJ. Geckos as springs: Mechanics explain across-species scaling of adhesion. PLoS ONE. 2015; 10(9): e0134604. DOI:10.1371/journal.pone.0134604.
- King DR, Bartlett MD, Nalbach M, Irschick DJ, Crosby AJ. “High Strength Reversible Adhesive Closures.” Journal of Polymer Science: Part B: Polymer Physics. 2017; DOI:10.1002/polb.24427.
- Imburgia MJ, Kuo C-Y, Briggs DR, Irschick DJ, Crosby AJ. “Effects of Digit Orientation on Gecko Adhesive Force Capacity: Synthetic and Behavioral Studies.” Integrative and Comparative Biology. 2019; 59(1):182-192. DOI:10.1093/icb/icz024.
Patents
- Alfred J. Crosby, Andrew B. Croll, Michael Bartlett, Daniel J. King. High Capacity Easy Release Extended Use Attachment Pad, US Application: 20140030490.
- Alfred J. Crosby and Michael Bartlett. Double- and Multi- Sided Adhesive Devices, US9395038, July 19, 2016.
- Alfred J. Crosby, Duncan J. Irschick, Michael Bartlett, and Daniel King. High-Capacity Easy Release Extended Use Adhesive Closure Devices, US Application: 20140304953.
- Alfred J. Crosby, Duncan J. Irschick, Michael Bartlett and Daniel King. Devices for Application and Load Bearing of Flexible Adhesive and Method of Using the Same, US9182075, November 10, 2015.
- Alfred J. Crosby, Duncan J. Irschick, Michael Bartlett, Daniel King. Weight-bearing Adhesives with Adjustable Angles, US9440416, September 13, 2016.
- Alfred J. Crosby, Daniel R. King, Michael D. Bartlett, Duncan J. Irschick. Weight-bearing Adhesives with Adjustable Angles, US2016/0375654 A1, December 29, 2016.