Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Touch-sensitive plastic skin heals itself

A researcher slices the self-healing skin with a scalpel. Photo: Linda A. Cicero, Stanford News Service
A researcher slices the self-healing skin with a scalpel. Photo: Linda A. Cicero, Stanford News Service

Abstract:
Nobody knows the remarkable properties of human skin like the researchers struggling to emulate it. Not only is our skin sensitive, sending the brain precise information about pressure and temperature, but it also heals efficiently to preserve a protective barrier against the world. Combining these two features in a single synthetic material presented an exciting challenge for Stanford Chemical Engineering Professor Zhenan Bao and her team.

Touch-sensitive plastic skin heals itself

Stanford, CA | Posted on November 11th, 2012

Now, they have succeeded in making the first material that can both sense subtle pressure and heal itself when torn or cut. Their findings will be published on November 11 in the journal Nature Nanotechnology.

In the last decade, there have been major advances in synthetic skin, said Bao, the study's principal investigator, but even the most effective self-healing materials had major drawbacks. Some had to be exposed to high temperatures, making them impractical for day-to-day use. Others could heal at room temperature, but repairing a cut changed their mechanical or chemical structure, so they could only heal themselves once. Most importantly, no self-healing material was a good bulk conductor of electricity, a crucial property.

"To interface this kind of material with the digital world, ideally you want them to be conductive," said Benjamin Chee-Keong Tee, first author of the paper.

A NEW RECIPE

The researchers succeeded by combining two ingredients to get what Bao calls "the best of both worlds" - the self-healing ability of a plastic polymer and the conductivity of a metal.

They started with a plastic consisting of long chains of molecules joined by hydrogen bonds - the relatively weak attractions between the positively charged region of one atom and the negatively charged region of the next.

"These dynamic bonds allow the material to self-heal," said Chao Wang, a co-first author of the research. The molecules easily break apart, but then when they reconnect, the bonds reorganize themselves and restore the structure of the material after it gets damaged, he said. The result is a bendable material, which even at room temperature feels a bit like saltwater taffy left in the fridge.

To this resilient polymer, the researchers added tiny particles of nickel, which increased its mechanical strength. The nanoscale surfaces of the nickel particles are rough, which proved important in making the material conductive. Tee compared these surface features to "mini-machetes," with each jutting edge concentrating an electrical field and making it easier for current to flow from one particle to the next.

The result was a polymer with uncommon characteristics. "Most plastics are good insulators, but this is an excellent conductor," Bao said.

BOUNCING BACK

The next step was to see how well the material could restore both its mechanical strength and its electrical conductivity after damage.

The researchers took a thin strip of the material and cut it in half with a scalpel. After gently pressing the pieces together for a few seconds, they found the material gained back 75 percent of its original strength and electrical conductivity. The material was restored close to 100 percent in about 30 minutes. "Even human skin takes days to heal. So I think this is quite cool," said Tee.

What's more, the same sample could be cut repeatedly in the same place. After 50 cuts and repairs, a sample withstood bending and stretching just like the original.

The composite nature of the material created a new engineering challenge for the team. Bao and her co-authors found that although nickel was key to making the material strong and conductive, it also got in the way of the healing process, preventing the hydrogen bonds from reconnecting as well as they should.

For future generations of the material, Bao said the team might adjust the size and shape of the nanoparticles, or even the chemical properties of the polymer, to get around this trade-off.

Nonetheless, Wang said the extent of these self-healing properties was truly surprising: "Before our work, it was very hard to imagine that this kind of flexible, conductive material could also be self-healing."

SENSITIVE TO THE TOUCH

The team also explored how to use the material as a sensor. For the electrons that make up an electrical current, trying to pass through this material is like trying to cross a stream by hopping from stone to stone. The stones in this analogy are the nickel particles, and the distance separating them determines how much energy an electron will need to free itself from one stone and move to another.

Twisting or putting pressure on the synthetic skin changes the distance between the nickel particles and, therefore, the ease with which electrons can move. These subtle changes in electrical resistance can be translated into information about pressure and tension on the skin.

Tee says that the material is sensitive enough to detect the pressure of a handshake. It might, therefore, be ideal for use in prosthetics, Bao added. The material is sensitive not only to downward pressure but also to flexion, so a prosthetic limb might someday be able to register the degree of bend in a joint.

Tee pointed out other commercial possibilities. Electrical devices and wires coated in this material could repair themselves and get electricity flowing again without costly and difficult maintenance, particularly in hard-to-reach places, such as inside building walls or vehicles.

Next up, Bao said the team's goal is to make the material stretchy and transparent, so that it might be suitable for wrapping and overlaying electronic devices or display screens.

Ranulfo Allen, a graduate chemical engineering student, also contributed to this research.

The research was supported by the Air Force Office of Scientific Research (AFOSR).

This article was written by Kelly Servick, a science-writing intern working for the Stanford University School of Engineering.

####

For more information, please click here

Contacts:
Andrew Myers

650-736-2245

Copyright © Stanford School of Engineering

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

The relationship between charge density waves and superconductivity? It's complicated July 19th, 2018

Sirrus's Issued Patent Portfolio Continues To Accelerate July 18th, 2018

FEFU scientists reported on toxicity of carbon and silicon nanotubes and carbon nanofibers: Nanoparticles with a wide range of applying, including medicine, damage cells of microalgae Heterosigma akashivo badly. July 18th, 2018

In borophene, boundaries are no barrier: Rice U., Northwestern researchers make and test atom-thick boron's unique domains July 17th, 2018

Display technology/LEDs/SS Lighting/OLEDs

DNA drives design principles for lighter, thinner optical displays: Lighter gold nanoparticles could replace thicker, heavier layered polymers used in displays’ back-reflectors June 27th, 2018

Nanomaterials could mean more algae outbreaks for wetlands, waterways: High tech metal particles may inadvertently take a toll on aquatic life June 26th, 2018

Making quantum puddles: Physicists discover how to create the thinnest liquid films ever June 13th, 2018

Getting electrons to move in a semiconductor: Gallium oxide shows high electron mobility, making it promising for better and cheaper devices April 24th, 2018

Govt.-Legislation/Regulation/Funding/Policy

The relationship between charge density waves and superconductivity? It's complicated July 19th, 2018

FEFU scientists reported on toxicity of carbon and silicon nanotubes and carbon nanofibers: Nanoparticles with a wide range of applying, including medicine, damage cells of microalgae Heterosigma akashivo badly. July 18th, 2018

In borophene, boundaries are no barrier: Rice U., Northwestern researchers make and test atom-thick boron's unique domains July 17th, 2018

Tuning into quantum: Scientists unlock signal frequency control of precision atom qubits July 16th, 2018

Nanomedicine

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication July 13th, 2018

UMBC researchers develop nanoparticles to reduce internal bleeding caused by blast trauma July 13th, 2018

Researchers identify cost-cutting option in treating nail fungus with nanotechnology: GW researcher Adam Friedman, M.D., studied the potential use of nitric oxide-releasing nanoparticles to improve onychomycosis treatment July 11th, 2018

New sensor technology enables super-sensitive live monitoring of human biomolecules July 3rd, 2018

Materials/Metamaterials

In borophene, boundaries are no barrier: Rice U., Northwestern researchers make and test atom-thick boron's unique domains July 17th, 2018

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides July 13th, 2018

Carbon is the new black: Researchers use carbon nanotubes to develop clothing that can double as batteries July 10th, 2018

High-power electronics keep their cool with new heat-conducting crystals July 6th, 2018

Announcements

The relationship between charge density waves and superconductivity? It's complicated July 19th, 2018

Sirrus's Issued Patent Portfolio Continues To Accelerate July 18th, 2018

FEFU scientists reported on toxicity of carbon and silicon nanotubes and carbon nanofibers: Nanoparticles with a wide range of applying, including medicine, damage cells of microalgae Heterosigma akashivo badly. July 18th, 2018

In borophene, boundaries are no barrier: Rice U., Northwestern researchers make and test atom-thick boron's unique domains July 17th, 2018

Military

In borophene, boundaries are no barrier: Rice U., Northwestern researchers make and test atom-thick boron's unique domains July 17th, 2018

UMBC researchers develop nanoparticles to reduce internal bleeding caused by blast trauma July 13th, 2018

Carbon is the new black: Researchers use carbon nanotubes to develop clothing that can double as batteries July 10th, 2018

High-power electronics keep their cool with new heat-conducting crystals July 6th, 2018

Automotive/Transportation

Leti and Oscaro Partner on Leti’s New Low-Power, Low-Cost Transceiver to Track Parcels July 12th, 2018

GLOBALFOUNDRIES Surpasses $2 Billion in Design Win Revenue on 22FDX® Technology : With 50 client designs and growing, 22FDX proves its value as a cost-effective solution for power-sensitive applications July 9th, 2018

Leti & Partners Launch Pilot Program to Assess New Perception Sensors for Autonomous Vehicles July 5th, 2018

GLOBALFOUNDRIES to Deliver Socionext’s Next Generation Graphics Controller for Advanced In-Vehicle Display Applications: 55nm LPx platform, with SST’s highly reliable embedded SuperFlash®, enables enhanced features and security protection for remote display applications June 28th, 2018

Construction

Weak hydrogen bonds key to strong, tough infrastructure: Rice University lab simulates polymer-cement composites to find strongest, toughest materials January 29th, 2018

The next generation of power electronics? Gallium nitride doped with beryllium: How to cut down energy loss in power electronics? The right kind of doping November 9th, 2017

Corrosion in real time: UCSB researchers get a nanoscale glimpse of crevice and pitting corrosion as it happens September 14th, 2017

Here's a tip: Indented cement shows unique properties: Rice University models reveal nanoindentation can benefit crystals in concrete July 20th, 2017

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project