New devices may turn electric arm into "body powered" arm some time in the future

With grip details required for interacting with every day environment not understood in sufficient detail to build one (1) single terminal device to suit us all, upper limb prosthetics is not an industry that has it easy. Currently, all major players ride one peculiar Dead Horse (at least so far) - the "myoelectric prosthesis". As active prosthetic control and motion require power, power sources are a relevant subject.


The innovation of myoelectric arms from back in the fifties has not been significantly improved yet. One electrode opens it, one closes it, they are heavy, sockets are hard and painful, they are unreliable and cheap electronics but absolute dream prices.

Innovation costs too much so why not Ride A Dead Horse and re-label. While some relabeling has been attempted - calling myoelectric prostheses "bionic" without actually living up to the term or even understanding it, or calling it "thought controlled" without actually building relevant innovations to actually implement this, the industry fails the users so far. Non disable people conjure up Potemkin hands for other non disable people and amputees are told to shut up and be happy, or they are intimidated, or ignored.

The industry is not particularly far either. The Otto Bock Michelangelo hand was advertised a while back - but it is far from being available. It appears that Otto Bock was not able to patent most of it either, has issues getting cosmetic gloves to fold around the thumb, will start first user tests only in Vienna and only in 2011. After a first wave of enthusiastic user/advertiser videos, the iLimb turns out to be neither particularly functional nor stable. The Fluid Hand never made it, the Vincent Hand successor website show cases a stale page since a while. The Contineo hand prototype never saw any visible improvement. All that has happened before - read the Carnes arm story and you will see that with the same clients attracting the same key players, history will repeat itself.

The problem is that vanity, misunderstanding of actual needs, lack of engineering ingenuity and insight into the advantages of existing power of an amputee causes developments that are far beyond being useful. Current engineers probably see mechanical design as a lost art - yet, it is the very pinnacle of arm prosthetics. It is the very essence of building these parts.

The other problem is that amputees usually have neither inclination nor time to see to it that parts are being built that work, that are worth putting on, that actually solve problems. There are some notable exceptions. Hugh Herr builds prosthetic legs, Bob Radocy builds prosthetic upper extremity parts for sports and recreation, and Dan Horkey puts art on the stuff.

But the other ones? I know of a Otto Bock Sensor Hand Speed user that switches that particular feature that makes it an "innovation" off as it is that irritating. I hear of iLimb users that are not satisfied with the hand - noise, failure, components not holding up. I am also not impressed by physical features - weight, weight distribution, socket, wrist / socket / hand combination - of myoelectric arms. Nor are my insurance representatives that expected recent models - iLimb, Michelangelo hand - to remedy known problems rather than giving old technology a new glossy look.

Riding a Dead Horse

The art of Riding a Dead Horse is well described.

Dakota tribal wisdom says that when you discover you are riding a dead horse, the best strategy is to dismount. However, in business we often try other strategies with dead horses, including the following:

Buying a stronger whip.

Changing riders.

Saying things like "This is the way we always have ridden this horse."

Appointing a committee to study the horse.

Arranging to visit other sites to see how they ride dead horses.

Increasing the standards to qualify as a dead horse rider.

Appointing a tiger team to revive the dead horse.

Pass legislation declaring that "This horse is not dead."

Unilaterally declaring, "no horse is too dead to beat."

Blaming the horse's parents.

Providing additional funding to increase the horse's performance.

Do a Cost Analysis Study to see if contractors can ride the horse cheaper.

Declare the horse is "better, faster and cheaper" dead.

Revisit the performance requirements for horses.

Promote the dead horse to a supervisory position.

Writing academic papers about otherwise useless gadgets under the label of "prosthetic hands" is a well established black art that has helped many academics since decades. Were it different in that we actually benefited from any of these I guess we'd know it by now and some el-cheapo-cable snip would not be news these days. But face it, we didn't, and it is.

If manufacturers could pull it off with upper extremity prosthetics, they would actually sell cheapest electronics - gadget motors, plastic parts, some telephone wire - for prices between 30'000 to 80'000$. They try to be more successful than the automobile industry in terms of turning cheap materials into gold - if they succeed, that is. When an executive of Otto Bock sees his main calling in expensive yachts but wants to get financing through public insurances then we do have a problem. Problem is with pulling it off - because these days, even insurances realized that the people they will have to look out for may not benefit as much as the sales people try to promise. If insurance representatives are not stupid, they will send their clients some other way. Try body powered. Try Becker Hands, try V2P, try Hosmer, try Regal Prosthesis, try Utah Arm, try Puppchen wrist.

  • Long term shoulder / neck strain is best avoided with a light weight prosthesis that allows for halfways acceptable if not optimal working angles. For various tasks you either need an extremely flexible hugely underactuated complex joint setup or, far more realistically, a quick release wrist and a number of different terminal devices. Enter the body powered prosthesis.
  • Long term shoulder / neck strain is best avoided with a proper weight distribution of the prosthetic arm. As long as you have to schlepp the car battery with you and a myo hand / wrist that weighs a ton on the end of your prosthetic arm, that will not work. Even Michelangelo show presenters pull up that shoulder - watch the videos, they can't hide it. So you want a better weight distribution, you want a lower weight. Enter the body powered prosthesis.
  • In a recent twist of fate they offer complex implant type technology to generate electric energy from your body (cool, see below). These little film elements are wonder works of technology. But what was wrong with using my body's crude energy right away? Enter the body powered prosthesis.

Power sources and power generation is a real problem in upper extremity prosthetics. Unless one builds a well functioning body powered prosthesis. There, body power is used. As the name implies. No batteries, no motors, saves weight, cost, reduces failure and far better socket constructions. It wasn't that hard now and didn't hurt this time, did it? Of course this rant only addresses upper limb prosthetics.

These little generators were built for powering far smaller devices - maybe injection pumps, LED displays for continuous blood sugar monitoring, prosthetic eye implant based cameras and other small stuff we will want in the future.

From Nanoletters:

The piezoelectric generation of perovskite BaTiO3 thin films on a flexible substrate has been applied to convert mechanical energy to electrical energy for the first time. Ferroelectric BaTiO3 thin films were deposited by radio frequency magnetron sputtering on a Pt/Ti/SiO2/(100) Si substrate and poled under an electric field of 100 kV/cm. The metal?insulator (BaTiO3)?metal-structured ribbons were successfully transferred onto a flexible substrate and connected by interdigitated electrodes. When periodically deformed by a bending stage, a flexible BaTiO3 nanogenerator can generate an output voltage of up to 1.0 V. The fabricated nanogenerator produced an output current density of 0.19 ?A/cm2 and a power density of 7 mW/cm3. The results show that a nanogenerator can be used to power flexible displays by means of mechanical agitations for future touchable display technologies.

From Eurekalert:

The team of Prof. Keon Jae Lee (KAIST, Dept. of Materials Science and Engineering) and Prof. Zhong Lin Wang (Georgia Institute of Technology, Dept. of Materials Science and Engineering) has developed new forms of highly efficient, flexible nanogenerator technology using the freely bendable piezoelectric ceramic thin film nano-materials that can convert tiny movements of the human body (such as heart beats and blood flow) into electrical energy.

The piezoelectric effect refers to voltage generation when pressure or bending strength is applied to piezoelectric materials. The ceramics, containing a perovskite structure, have a high piezoelectric efficiency. Until now, it has been very difficult to use these ceramic materials to fabricate flexible electronic systems due to their brittle property.

The research team, however, has succeeded in developing a bio-eco-friendly ceramic thin film nanogenerator that is freely bendable without breakdown.

Nanogenerator technology, a power generating system without wires or batteries, combines nanotechnology with piezoelectrics that can be used not only in personal mobile electronics but also in bio-implantable sensors or as an energy source for micro robots. Energy sources in nature (wind, vibration, and sound) and biomechanical forces produced by the human body (heart beats, blood flow, and muscle contraction/relaxation) can infinitely produce nonpolluting energy.

Prof. Keon Jae Lee (KAIST) was involved in the first co-invention of "High Performance Flexible Single Crystal Electronics" during his PhD course at the University of Illinois at Urbana-Champaign. This nanogenerator technology, based on the previous invention, utilized the similar protocol of transferring ceramic thin film nano-materials on flexible substrates and produced voltage generation between electrodes.

Prof. Zhong Lin Wang (Georgia Tech, inventor of the nanogenerator) said, "This technology can be used to turn on an LED by slightly modifying circuits and operate touchable flexible displays. In addition, thin film nano-materials ('barium titanate') of this research have the property of both high efficiency and lead-free bio compatibility, which can be used in future medical applications."

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - New devices may turn electric arm into "body powered" arm some time in the future; published 20/11/2010, 21:10; URL:

BibTeX: @MISC{schweitzer_wolf_1624072537, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - New devices may turn electric arm into "body powered" arm some time in the future}}, month = {November},year = {2010}, url = {}}