Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sandia seeks better neural control of prosthetics for amputees

22.02.2012
Sandia National Laboratories researchers, using off-the-shelf equipment in a chemistry lab, have been working on ways to improve amputees’ control over prosthetics with direct help from their own nervous systems.
Organic materials chemist Shawn Dirk focuses a projector during work on neural interfaces, which are aimed at improving amputees’ control over prosthetics with direct help from their own nervous systems. Focusing prior to exposing polymers ensures that researchers pattern the desired feature sizes for the interfaces. (Photo by Randy Montoya) Click on the thumbnail for a high-resolution image.

Organic materials chemist Shawn Dirk, robotics engineer Steve Buerger and others are creating biocompatible interface scaffolds. The goal is improved prosthetics with flexible nerve-to-nerve or nerve-to-muscle interfaces through which transected nerves can grow, putting small groups of nerve fibers in close contact to electrode sites connected to separate, implanted electronics.

Neural interfaces operate where the nervous system and an artificial device intersect. Interfaces can monitor nerve signals or provide inputs that let amputees control prosthetic devices by direct neural signals, the same way they would control parts of their own bodies.

Sandia’s research focuses on biomaterials and peripheral nerves at the interface site. The idea is to match material properties to nerve fibers with flexible, conductive materials that are biocompatible so they can integrate with nerve bundles.

“There are a lot of knobs we can turn to get the material properties to match those of the nerves,” Dirk said.

Buerger added, “If we can get the right material properties, we could create a healthy, long-lasting interface that will allow an amputee to control a robotic limb using their own nervous system for years, or even decades, without repeat surgeries.”

Researchers are looking at flexible conducting electrode materials using thin evaporated metal or patterned multiwalled carbon nanotubes.

The work is in its early stages and it might be years before such materials reach the market. Studies must confirm they function as needed, then they would face a lengthy Food and Drug Administration approval process.

But the need is there. The Amputee Coalition estimates 2 million people in the United States are living with limb loss. The Congressional Research Service reports more than 1,600 amputations involving U.S. troops between 2001 and 2010, more than 1,400 of those associated with the fighting in Iraq and Afghanistan. Most were major limb amputations.

Robotics engineer Steve Buerger displays implantable and wearable neural interface electronics developed by Sandia as he sits in the prosthetics lab with a display of prosthetic components. He is part of a research team that is working on ways to improve amputees’ control over prosthetics with direct help from their own nervous system. (Photo by Randy Montoya) Click on the thumbnail for a high-resolution image.

Before joining Sandia, Buerger worked with a research group at MIT developing biomedical robots, including prosthetics. Sandia’s robotics group was developing prosthetics before his arrival as part of U.S. Department of Energy-sponsored humanitarian programs to reduce proliferation risks.

Robotics approached the problem from a technical point of view, looking at improving implantable and wearable neural interface electronics. However, Buerger said that didn’t address the central issue of interfacing with nerves, so researchers turned to Dirk’s team.

“This goes after the crux of the problem,” he said.

The challenges are numerous. Interfaces must be structured so nerve fibers can grow through. They must be mechanically compatible so they don’t harm the nervous system or surrounding tissues, and biocompatible to integrate with tissue and promote nerve fiber growth. They also must incorporate conductivity to allow electrode sites to connect with external circuitry, and electrical properties must be tuned to transmit neural signals.

Dirk presented a paper on potential neural interface materials at the winter meeting of the Materials Research Society, describing Sandia’s work in collaboration with the University of New Mexico and MD Anderson Cancer Center in Houston. Co-authors are Buerger, UNM assistant professor Elizabeth Hedberg-Dirk, UNM graduate student and Sandia contractor Kirsten Cicotte, and MD Anderson’s Patrick Lin and Gregory Reece.

The researchers began with a technique first patented in 1902 called electrospinning, which produces nonwoven fiber mats by applying a high-voltage field between the tip of a syringe filled with a polymer solution and a collection mat. Tip diameter and solution viscosity control fiber size.

Collaborating with UNM’s Center for Biomedical Engineering and department of chemical engineering, Sandia researchers worked with polymers that are liquid at room temperature. Electrospinning these liquid polymers does not result in fiber formation, and the results are sort of like water pooling on a flat surface. To remedy the lack of fiber formation, they electrospun the material onto a heated plate, initiating a chemical reaction to crosslink the polymer fibers as they were formed, Dirk said.

This tiny test structure was fabricated from the same photo-crosslinkable PDMS material which has been implanted into rats as part of the MD Anderson Cancer Center-UNM-Sandia collaboration. The test structure helps researchers characterize the performance of their microprojection lithography system. (Photo by Randy Montoya) Click on the thumbnail for a high-resolution image.

Researchers were able to tune the conductivity of the final composite with the addition of multiwalled carbon nanotubes.

The team electrospun scaffolds with two types of material — PBF, or poly(butylene fumarate), a polymer developed at UNM and Sandia for tissue engineering, and PDMS, or poly(dimethylsiloxane).
PBF is a biocompatible material that’s biodegradable so the porous scaffold would disintegrate, leaving the contacts behind. PDMS is a biocompatible caulk-like material that is not biodegradable, meaning the scaffold would remain. Electrodes on one side of the materials made them conductive.

Sandia’s work was funded through a late-start Laboratory Directed Research & Development (LDRD) project in 2010; afterward the researchers partnered with MD Anderson for implant tests. Sandia and MD Anderson are seeking funding to continue the project, Dirk said.

Buerger said they’re using their proof-of-concept work to obtain third-party funding “so we can bring this technology closer to something that will help our wounded warriors, amputees and victims of peripheral nerve injury.”

Sandia and UNM have applied for a patent on the scaffold technique. Sandia also filed two separate provisional patent applications, one in partnership with MD Anderson and the other with UNM, and the partners expect to submit full applications this year.

The MD Anderson collaboration came about because then-Sandia employee Dick Fate, an MD Anderson patient who’d lost his left leg to cancer, thought the hospital and the Labs were a natural match. He brokered an invitation from Sandia to the hospital, which led to the eventual partnership.

Click here to view footage of the microstereolithograph technique used by the Sandia team working on neural interfaces. (Or download as a 18 MB WMV format, or view in HD on YouTube.)

Fate, who retired in 2010, views the debilitating effect of rising health care costs on the nation’s economy as a national security issue.

“To me it seems like such a logical match, the best engineering lab in the country working with the best medical research institution in the country to solve some of these big problems that are nearly driving this country bankrupt,” he said.

After Sandia researchers came up with interface materials, MD Anderson surgeons sutured the scaffolds into legs of rats between a transected peroneal nerve. After three to four weeks, the interfaces were evaluated.

Samples fabricated from PBF turned out to be too thick and not porous enough for good nerve penetration through the scaffold, Dirk said. PDMS was more promising, with histology showing the nerve cells beginning to penetrate the scaffold. The thickness of the electrospun mats, about 100 microns, were appropriate, Dirk said, but weren’t porous enough and the pore pattern wasn’t controlled.

The team’s search for a different technique to create the porous substrates led to projection microstereolithography, developed at the University of Illinois Urbana-Champaign as an inexpensive classroom outreach tool. It couples a computer with a PowerPoint image to a projector whose lens is focused on a mirror that reflects into a beaker containing a solution.

Using a laptop and a projector, Dirk said the researchers initially tried using a mirror and a 3X magnifying glass, but abandoned that because it produced too much distortion. They now use the magnifying glass to focus UV light onto the PDMS-coated silicon wafer to form thin porous membranes.

While the lithography technique is not new, “we developed new materials that can be used as biocompatible photo crosslinkable polymers,” Dirk said.
The technique allowed the team to create a regular array of holes and to pattern holes as small as 79 microns. Now researchers are using other equipment to create more controlled features.

“It’s exciting because we’re getting the feature size down close to what is needed,” Buerger said.

Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.

Sandia news media contact: Sue Holmes, sholmes@sandia.gov, (505) 844-6362

Sue Holmes | EurekAlert!
Further information:
http://www.sandia.gov

More articles from Life Sciences:

nachricht Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University

nachricht Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017
25.04.2017 | Laser Zentrum Hannover e.V.

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

NASA's Fermi catches gamma-ray flashes from tropical storms

25.04.2017 | Physics and Astronomy

Researchers invent process to make sustainable rubber, plastics

25.04.2017 | Materials Sciences

Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017

25.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>