Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Rocket-powered mechanical arm could revolutionize prosthetics

21.08.2007
Combine a mechanical arm with a miniature rocket motor: The result is a prosthetic device that is the closest thing yet to a bionic arm.

A prototype of this radical design has been successfully developed and tested by a team of mechanical engineers at Vanderbilt University as part of a $30 million federal program to develop advanced prosthetic devices.

“Our design does not have superhuman strength or capability, but it is closer in terms of function and power to a human arm than any previous prosthetic device that is self-powered and weighs about the same as a natural arm,” says Michael Goldfarb, the professor of mechanical engineering who is leading the effort.

The prototype can lift (curl) about 20 to 25 pounds – three to four times more than current commercial arms – and can do so three to four times faster. “That means it has about 10 times as much power as other arms despite the fact that the design hasn’t been optimized yet for strength or power,” he says.

The mechanical arm also functions more naturally than previous models. Conventional prosthetic arms have only two joints, the elbow and claw. By comparison, the prototype’s wrist twists and bends and its fingers and thumb open and close independently.

The Vanderbilt arm is the most unconventional of three prosthetic arms under development by the Defense Advanced Research Project Agency (DARPA) program. The other two are being designed by researchers at the Advanced Physics Laboratory at Johns Hopkins University in Baltimore who head the program. Those arms are powered by batteries and electric motors. At the same time, the program is supporting teams of neuroscientists at the University of Utah, California Institute of Technology and the Rehabilitation Institute of Chicago who are developing advanced methods for controlling the arms by connecting them to nerves in the users’ bodies or brains.

“Battery power has been adequate for the current generation of prosthetic arms because their functionality is so limited that people don’t use them much,” Goldfarb says. “The more functional the prosthesis, the more the person will use it and the more energy it will consume.”

At a certain point, the weight of the batteries required to provide the energy to operate the arm for a reasonable period becomes a problem. It was the poor power-to-weight ratio of the batteries that drove Goldfarb to look for alternatives in 2000 while he was working on a previous exoskeleton project for DARPA. He decided to miniaturize the monopropellant rocket motor system that is used by the space shuttle for maneuvering in orbit. His adaptation impressed the Johns Hopkins researchers, so they offered him $2.7 million in research funding to apply this approach to the development of a prosthetic arm.

Goldfarb’s power source is about the size of a pencil and contains a special catalyst that causes hydrogen peroxide to burn. When hydrogen peroxide burns, it produces pure steam. The steam is used to open and close a series of valves. The valves are connected to the spring-loaded joints by belts made of a special monofilament used in appliance handles and aircraft parts. A small sealed canister of hydrogen peroxide that easily fits in the upper arm can provide enough energy to power the device for 18 hours of normal activity.

One of the researchers’ concerns was protecting the wearer and others in close proximity from the heat generated by the device. By covering the hottest parts with special insulating plastic, they were able to reduce surface temperatures enough so they are safe to touch. The steam exhaust was also a problem, which they decided to handle in as natural a fashion as possible: by venting it through a porous cover, where it evaporates like natural perspiration. “The amount of water involved is about the same as a person would normally sweat from their arm in a warm day,” Goldfarb says.

The Vanderbilt team built a first prototype that ran on condensed gas. This allowed them to test the basic design and address the basic problems of control, leakage and noise. After getting it to work properly on “cold gas,” the engineers created a second prototype with the hydrogen peroxide power source, which produces steam at 450 degrees Fahrenheit. They quickly determined that the material they had used for the belts couldn’t take the heat. After an extended process of trial and error before they found a commercial material that was strong enough and could withstand the high temperatures. After solving this and a number of other smaller problems, the researchers got the second prototype working properly by the end of June.

In the fall, DARPA’s “Revolutionizing Prosthetics 2009” program will move to its second stage. Even though his team has met all its research milestones and produced a working prototype, Goldfarb is not certain that their arm will be included. “DARPA set a goal of developing a commercially available arm in two years. Because of our novel power source, the process of proving that our design is safe and getting regulatory approval for its use will probably take longer than that,” he says.

If DARPA decides it cannot continue supporting the arm’s development for this reason, Goldfarb is confident that he can get alternative funding. “We have made so much progress and gotten such positive feedback from the research community that I’m certain we’ll be able to keep going,” he says.

Vanderbilt University is a private research university of approximately 6,300 undergraduates and 4,600 graduate and professional students. Founded in 1873, the University comprises 10 schools, a public policy institute, a distinguished medical center and The Freedom Forum First Amendment Center. Vanderbilt, ranked as one of the nation’s top universities, offers undergraduate programs in the liberal arts and sciences, engineering, music, education and human development, and a full range of graduate and professional degrees.

For more news about Vanderbilt, visit the News Service homepage at www.vanderbilt.edu/News.

David F. Salisbury | Vanderbilt University
Further information:
http://www.vanderbilt.edu/News.

More articles from Health and Medicine:

nachricht Study suggests possible new target for treating and preventing Alzheimer's
02.12.2016 | Oregon Health & Science University

nachricht The first analysis of Ewing's sarcoma methyloma opens doors to new treatments
01.12.2016 | IDIBELL-Bellvitge Biomedical Research Institute

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>