text-only page produced automatically by LIFT Text Transcoder Skip all navigation and go to page contentSkip top navigation and go to directorate navigationSkip top navigation and go to page navigation
National Science Foundation Home National Science Foundation - Mathematical & Physical Sciences (MPS)
Mathematical & Physical Sciences (MPS)
design element
MPS Home
About MPS
Funding Opportunities
Awards
News
Events
Discoveries
Publications
Advisory Committee
Career Opportunities
2013-2014 Distinguished Lecture Series
View MPS Staff
MPS Organizations
Astronomical Sciences (AST)
Chemistry (CHE)
Materials Research (DMR)
Mathematical Sciences (DMS)
Physics (PHY)
Office of Multidisciplinary Activities (OMA)
Proposals and Awards
Proposal and Award Policies and Procedures Guide
  Introduction
Proposal Preparation and Submission
bullet Grant Proposal Guide
  bullet Grants.gov Application Guide
Award and Administration
bullet Award and Administration Guide
Award Conditions
Other Types of Proposals
Merit Review
NSF Outreach
Policy Office
Other Site Features
Special Reports
Research Overviews
Multimedia Gallery
Classroom Resources
NSF-Wide Investments

Email this pagePrint this page

Discovery
Following in the Footsteps of Nature

Researchers move one step closer to nature with the development of polymers and directional adhesion that follow the workings of a gecko's foot

Video showing gecko feet.
Video available View video

NSF Funded researchers have collaborated to develop a gecko-like synthetic adhesive.
Credit and Larger Version

February 9, 2010

Nanotechnology has not only brought nature and engineering closer together; it has encouraged collaboration among researchers of different disciplines. In one such collaboration, two researchers drew on the extraordinary stickiness of a gecko's foot to develop a synthetic adhesive to help robots scale walls.

NSF-funded researchers Mark Cutkosky, an engineer at Stanford University, and Kellar Autumn, a biologist at Lewis and Clark College, have collaborated to develop a gecko-like synthetic adhesive that functions like real gecko bristles for climbing applications. The team discovered the fundamental physics principles underlying gecko adhesion, which enabled the invention of an adhesive nanostructure.

The Tokay gecko, one of the largest and heaviest geckos, served as inspiration.

"The challenge was simply to get robots to go where robots have never been able to go before, like up walls of buildings," said Cutkosky. "If robots can climb vertical surfaces, then they can do inspection of buildings and bridges and other hard- to-reach places."

Cutkosky received a four-year, $1 million National Science Foundation research grant that funded the development of the first gecko-like synthetic adhesive (GSA) that works like real gecko bristles. Autumn received two NSF grants for continued research on gecko adhesion. Cutkosky's team collaborated with Kellar Autumn and his gecko lab to determine whether a synthetic adhesive could be applied to robots.

"The collaboration with Mark's group has been incredibly productive. Based on micro-force measurements, we hypothesized that a coupling of shear force and adhesion was responsible for control of the geckos' attachment system," said Autumn.

A gecko's foot possesses a sophisticated adhesion system that uses van der Waals forces, which are the basic molecular attraction that exists between molecules. Van der Waals forces allow geckos to climb and hang on a smooth and vertical surfaces using one toe.

Cutkosky and his team have been designing bio-inspired robots which use van der Waals forces. Their most recent design is stickybot, a robot that has gecko-like pads, which allows it to scale walls and buildings.

Bio-inspired design on a nano scale

The intricate work of nature occurs on a tiny scale, below the limits of our vision. Beneath the surface of a gecko's foot is a three-level hierarchy of structures. The first level is made up of lamellae, which are a series of structures that look like flaps under a microscope. Then, the lamellae are divided into smaller structures called seate which are thinner than a human hair. Finally, the seate branch into tiny little ends called spatulae, which are only a couple of hundred nanometers in size.

"So what happens is that the gecko is able to conform to surfaces ranging from tens or hundreds of nanometers all the way up to centimeters," said Cutkosky. "It is very cool; it is sort of the poster child for complex hierarchical geometry, almost fractal in its nature."

The structures that compose the different levels in the hierarchy have a similar behavior at multiple length scales.

The gecko's toe structures are only adhesive when loaded in a particular direction and the gecko can control adhesion by aligning its microstructures and making intimate contact with the surface. Stickybot follows the same principles as a gecko, but needs to adjust the orientation of its feet as it climbs. This is to ensure that the toes are always loaded in the proper direction for adhesion.

Cutkosky and Autumn have built similar synthetic structures that follow the design of a gecko's foot. At present, they have created a two layer hierarchy of polymers with directional adhesion. This is good enough for stickybot to use to scale walls; however there is always room for improvement.

"It comes down to how much adhesion you are getting per unit area. The gecko can easily support its weight on one toe. In fact, it has lots to spare. Without the latest and greatest adhesives, I think stickybot can barely support its weight on one toe. We are nowhere near the gecko. Basically, it comes down to the weight of the robot and how many pascals of adhesion you can get from your material," said Cutkosky.

The pascal is a measurement of force per unit area which allows researchers, like Cutkosky, to determine how much stress the synthetic adhesion can tolerate. This helps gauge how the adhesive is developed and how it can be changed in the future.

The future of stickybot

Stickybot employs three main principles to climb smooth surfaces: hierarchical compliance to conform to levels from micrometers to centimeters, directional adhesion to smoothly engage and disengage from a surface, and force control to control frictional forces in the feet. Though stickybot can climb on vertical and smooth surfaces, Cutkosky hopes to develop a robot capable of climbing a wide variety of surfaces.

"We are continuing to try and improve the dry adhesive itself, but independent from that; we are working on a new stickybot. Making the ankles of the robot rotate is probably number one, but we also want to do more sensing and control. Right now stickybot doesn't have many sensors, so if it's climbing and starting to get into trouble, it doesn't know that and may fall," said Cutkosky.

Cutkosky and Autumn's research and collaboration have shown how materials science is attempting to follow nature.

"Nature has a huge advantage it can grow and differentiate cell by cell. Whereas, when we manufacture things we're always using processes that work top-down and so every layer is difficult and expensive for us," said Cutkosky.

--  Gwendolyn Morgan, (703) 292-7725 gmorgan@nsf.gov

Investigators
Thomas Kenny
Kellar Autumn
Mark Cutkosky
Kimberly Turner
Jacob Israelachvili

Related Institutions/Organizations
Stanford University
Lewis and Clark College
University of California-Santa Barbara

Locations
California

Related Programs
NanoManufacturing
Nano and Bio Mechanics

Related Awards
#0708367 NIRT: Reversible Frictional Adhesion of Natural and Bio-Inspired Multi-Scale Structures
#0847953 RUI: Comparative micromechanics of gecko setae: Effects of rate, substrate, and environment
#0900723 Collaborative Research: Electrically Controlled Nanofibrillar Surfaces for Cleaning and Adhesion

Total Grants
$1,365,442

Related Websites
Stanford: http://bdml.stanford.edu/twiki/bin/view/Rise/StickyBot
Gecko Lab Lewis and Clark: http://geckolab.lclark.edu/dept/Welcome.html

Photo of Sangbae Kim and Mark Cutkosky with the robot stickybot.
Sangbae Kim and Mark Cutkosky have developed a bio-inspired gecko robot called stickybot.
Credit and Larger Version

Photo of the robot stickybot.
Stickybot employs the same principles as a gecko through the use of dry adhesion to climb walls.
Credit and Larger Version

Photo of a gecko's foot.
A gecko's foot possesses a sophisticated adhesion system that uses van der Waals forces.
Credit and Larger Version



Email this pagePrint this page
Back to Top of page