Medical Plastics: Turning to the humble gecko

By Lou Reade
PRW

Published: January 23, 2013 12:27 pm ET
Updated: January 23, 2013 12:32 pm ET

Related to this story

Topics Medical, Polyurethane, Design, Materials Suppliers

NEW ORLEANS -- Polymers for use in the medical industry are most commonly processed in all the usual ways: injection molding, extrusion, blow molding.

But beyond the realms of standard medical devices, some curious and alien techniques come into effect.

These are being used in order to create intricate and detailed surfaces that have very specific medical effects.

For example, scientists in the United States have created microscopic polyurethane structures that mimic the way that a gecko's foot sticks to a surface.

Conventional adhesives are "pressure sensitive," and are widely effective, but not in all environments. They struggle in a vacuum, for example, or in aqueous environments – such as inside the human body.

For this reason, scientists are looking to develop adhesives that work using new mechanisms, such as by mimicking the gecko's foot – which leaves no sticky residue behind.

The pads on a gecko's feet are composed of millions of tiny "hairs": these make such intimate contact with the surface, that forces of molecular attraction – called Van der Waals forces – come into effect.

"Usually, you can never get close enough contact with a surface for this to happen," says Noshir Pesika, assistant professor in the chemical and biomolecular engineering department at Tulane University.

He has used photolithography – a technique normally used in the production of microchips – to create the special adhesive surfaces that mimic the gecko's foot. He has produced tiny polyurethane structures with microscopic features on the surface, which stick through "attraction" only.

The main body of the structure is a cylinder. On top of this, a series of tiny fibers protrude from the surface. These measure around 20 x 20 x 7 microns. It is these tiny fibers, or pads, that make intimate contact with a surface and stick to it via molecular attraction.

For comparison, the equivalent structure on a gecko's foot is on the nano-scale, and around a thousand times smaller.

However, these tiny structures on the gecko's foot are relatively stiff. Pesika's structures can be made more pliable, which improves surface contact. He estimates that his structures are around a hundred times weaker than a real gecko's foot. But he adds that a 1-foot-by-1-foot pad of his material could support the weight of a human.

"So far, we've made structures that are about 1.5 inches square," he said.

The samples were made at the Naval Research Laboratory in Washington.

A key attribute of the gecko's foot is its anisotropy: this means that it sticks firmly when sheared in one direction, but weakly in the other. It is this quality that allows the gecko to run quickly across the ceiling.

"The gecko's foot sticks strongly but comes off easily," he says.

Pesika has reproduced this effect by mimicking the structure of the gecko's foot, tilting the small fibers at an angle to create the anisotropy.

He points to a number of potential markets: space travel, where the vacuum of space can destroy conventional products; and in aqueous environments – which could include the inside of the human body.

"It could be used to make special sutures, which surgeons could 'stick and replace' in order to put them in the correct position," he said.

Pesika envisages an initial product in the form of a tape, but where the sticky surface is protected until it is needed. But launching a commercial product is likely to be some way off – and many challenges remain.

"To commercialize this, it would have to be made in a continuous process, rather than the batch process we're currently using," he said.

At the same time, researchers at the University of Akron are looking into the gripping power of the gecko's foot in wet conditions – in the hope that the results can be used to develop new types of bandage and other surgical products.

The gecko's foot naturally repels water, allowing it to stick to wet surfaces. The researchers, led by Alyssa Stark, have tested gecko toe hair adhesion in a series of scenarios: dry toe pads on dry, misted and wet surfaces; and soaked toe pads on dry, misted and wet glass.

The soaked toe pads showed low to no adhesion depending on the amount of wetness. Likewise, dry toe pads lost their adhesive grip increasingly with the amount of water applied to the surface upon which they were pulled.

For the experiments, geckos were pulled on a glass surface by a small harness placed around their midsections.

"We are gathering clues about how geckos interact with wet surfaces and this gives us ideas of how to design adhesives that work under water," said Ali Dhinojwala, chair of the department of polymer science.

"Nature gives us a certain set of rules that point us in the right direction. They help us understand limitations and how to manipulate materials."

Dhinojwala and colleagues have already developed a dry synthetic adhesive, comprised of carbon nanotubes, that outperforms nature's variety.

For a full version of this story, see www.PRW.com.


Comments

Medical Plastics: Turning to the humble gecko

By Lou Reade
PRW

Published: January 23, 2013 12:27 pm ET
Updated: January 23, 2013 12:32 pm ET

Post Your Comments


Back to story


More stories

Image

2014 sees modest sales increase, but profit decrease, for Dow Chemical

January 29, 2015 4:20 pm ET

Dow Chemical Co. delivered modest sales growth in 2014, but the firm's profit took a tumble.    More

Image

Resin prices continuing to tumble

January 29, 2015 2:24 pm ET

The ongoing slide in crude oil prices is taking commodity resin prices down as well.    More

Image

Materials firms look for stock rebound

January 29, 2015 1:52 pm ET

DuPont Co., A. Schulman Inc. and Rogers Corp. thrived amid the stock market chaos of 2014, but the other 12 publicly held materials firms tracked by...    More

Image

Chemtrusion, Mytex Indiana compounding plant set for expansion

January 29, 2015 1:35 pm ET

Japanese and American partners in a compounding plant in Indiana plan to expand the facility.    More

Image

DuPont-Chenguang JV to produce fluoroelastomers in China

January 29, 2015 12:30 pm ET

DuPont Fluoropolymer Solutions and Zhonghao Chenguang Chemical Research Institute Co. Ltd. are proceeding with a 50-50 joint venture to serve the fast...    More

Market Reports

Plastics in Automotive: Innovation & Emerging Trends

This special report newly released by PN and sponsored by The Conair Group examines current trends in the use of plastics in automotive, materials innovations and the changing landscape. It includes a review of legislative/regulatory activity impacting vehicle development and lightweighting, market opportunities & challenges for mold and toolmakers, innovative design strategies being implemented by major OEMs and suppliers, as well as a review of key indicators in Canada, Mexico, Brazil and China.

Learn more

Plastics Recycling Trends in North America

This report is a review and analysis of the North American Plastics Recycling Industry, including key trends and statistics based on 2013 performance. We examine market environment factors, regulatory issues, industry challenges, key drivers and emerging trends in post-consumer and post-industrial recycling.

Learn more

Injection Molding Market Analysis & Processor Rankings

Plastics News BUNDLED package contains our in-depth Market Analysis of the Injection Molding segment. You will gain keen insight on current trends and our economic outlook.

As a BONUS this includes PN's updated 2014 database of North American Injection Molders RANKED by sales volume. Sort, merge, mail & prospect by end market, materials processed, region, # of plants and more.

Learn more

Upcoming Plastics News Events

February 4, 2015 - February 6, 2015Plastics News Executive Forum 2015

June 2, 2015 - June 3, 2015Plastics Financial Summit - Chicago 2015

September 16, 2015 - September 18, 2015Plastics Caps & Closures - September 2015

More Events