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Category: Prototype development

How does a Helping Hand / LN 4 hand work [test report]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - How does a Helping Hand / LN 4 hand work [test report]; published December 17, 2018, 05:44; URL: https://www.swisswuff.ch/tech/?p=9027.

BibTeX: @MISC{schweitzer_wolf_1574228481, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - How does a Helping Hand / LN 4 hand work [test report]}}, month = {December},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=9027}}


I organized myself the opportunity to test a "Helping Hand" (also known as LN 4 hand) myself.

You know, the one that are being built as a feel-good exercise by business people and others, and that are given away to people that seem in need. It has its own website [link]. The Ellen Meadows Foundation specifically empowers not amputees, but non-disabled people. Verbally, they claim in their mission statement: "Inspire change in the world by empowering individuals to use their hands to support putting hands on people in need. We will not stop until anyone who needs a prosthetic hand has access to one". About the hand, they write: "Originally Ernie intended to design a functional prosthetic hand for children and adolescent land mine victims. Over time he developed a design for a low-cost, light, durable, functional prosthetic hand. He knew that this would help all who need a prosthetic hand and who could not afford the available alternatives".

That means:

  • They empower non-disabled people that have hands to use their hands. That is noble, I guess.
  • They will not stop until anyone that needs a prosthetic hand has access to one. The definition of a prosthetic hand is wide open, I guess,  but they precisely state their hand is functional and durable. That? We will see about that.

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Experienced user based advice for investors in the domain of prosthetic arms [technical guide for understanding the field]

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Wolf Schweitzer: Technical Below Elbow Amputee Issues - Experienced user based advice for investors in the domain of prosthetic arms [technical guide for understanding the field]; published July 26, 2018, 15:17; URL: https://www.swisswuff.ch/tech/?p=8702.

BibTeX: @MISC{schweitzer_wolf_1574228481, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Experienced user based advice for investors in the domain of prosthetic arms [technical guide for understanding the field]}}, month = {July},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8702}}


Investors may need to understand what prosthetic arms really are, how they come about, and what is there to be considered, before investing into a prosthetic arm component manufacturer or research spin off.

With a realistic estimate of around 85% rejection rate, the prosthetic arm industry so far is one of the most unsuccessful industries that there are both in high-tech and medicine technology.

Now, what usually keeps developments, market introductions and user feedback as well as improvement circles going is a successful social setting. Such a really successful circle, where respect combines with a striving for technical proficiency, in the context of prosthetic arms, appears to be largely absent. To a great part, this explains why the current status with regard to marketing, improving or successfully selling prosthetic arms is not a lot better than maybe sixty years ago.

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3D-print molded Protosil RTV 245 (durometer shore 40A) silicone covers for Toughware Equilux [proof of concept, demo of "bionic" grip]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - 3D-print molded Protosil RTV 245 (durometer shore 40A) silicone covers for Toughware Equilux [proof of concept, demo of "bionic" grip]; published February 4, 2018, 11:50; URL: https://www.swisswuff.ch/tech/?p=8248.

BibTeX: @MISC{schweitzer_wolf_1574228481, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - 3D-print molded Protosil RTV 245 (durometer shore 40A) silicone covers for Toughware Equilux [proof of concept, demo of "bionic" grip]}}, month = {February},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8248}}


It is sometimes more fun to present the technical results before or even instead of explaining exactly why.  So in short, I 3d-designed and then printed molds to make grip covers for really serious grip performance of a Toughware Equilux device.

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Case-study of a user-driven prosthetic arm design: bionic hand versus customized body-powered technology in a highly demanding work environment [article out]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Case-study of a user-driven prosthetic arm design: bionic hand versus customized body-powered technology in a highly demanding work environment [article out]; published January 4, 2018, 14:29; URL: https://www.swisswuff.ch/tech/?p=8066.

BibTeX: @MISC{schweitzer_wolf_1574228481, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Case-study of a user-driven prosthetic arm design: bionic hand versus customized body-powered technology in a highly demanding work environment [article out]}}, month = {January},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8066}}


 


This is a blog post of one of the rare focused and well based scientific journal articles that really explains how real work, body powered and myoelectric arms relate and go together for a unilateral right below elbow amputee in a physically demanding work environment.

The prior presentation of this paper [poster at Cybathlon symposium 2016], which had been more pragmatically worded (with me thinking people would know anyway), this was now written up as article and published. During that process, the reviewers clearly made great points of all kinds of aspects I never knew were not sky clear to everyone.

So maybe, writing a ~ 30 page case study with > 210 references does clarify stuff, at least potentially and for those that actually read it. But possibly, it still requires attention to even just read it.

Knowledge does not come easy, Highlander! (Nakano, in: Highlander III The Final Dimension)

 

If you are more interested in visionary posts, read about the gadget features of the prosthetic arm in Kingsmen: The Golden Circle [link]. And technically, myoelectric control did have it coming. That technology remained uncool for four decades [link].

Publication [link]

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Scientific approach taken for implementing a successfully marketable microprocessor-controlled knee - history of Otto Bock C-leg [lessons for prosthetic arms?]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Scientific approach taken for implementing a successfully marketable microprocessor-controlled knee - history of Otto Bock C-leg [lessons for prosthetic arms?]; published January 2, 2018, 15:10; URL: https://www.swisswuff.ch/tech/?p=7790.

BibTeX: @MISC{schweitzer_wolf_1574228481, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Scientific approach taken for implementing a successfully marketable microprocessor-controlled knee - history of Otto Bock C-leg [lessons for prosthetic arms?]}}, month = {January},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=7790}}


This blog post takes a few relevant observations, and assumptions, throws them up in the air and sees if they turn into sunshine.

  • If anything has brought us forward, it is also the ability to find relevant short cuts. We do not always have to invent the wheel when really we just want a variation of it.
  • If there is any acutal success story where academic research was required to leverage consumer market for a prosthetic limb, it is that of Otto Bock's C-leg.
  • If we can understand what the concepts are for getting a C-leg successfuly built, marketed and sold, we should be able to take generalized aspects of it to formulate success elements for prosthetic hands, grippers or arms.

Background

While the idea of a microprocessor controlled knee was created earlier [link], no marketable solution was available in due course. "In the early 1990s, Kelly James, an engineer at the University of Alberta, Edmonton, Canada, developed the C-Leg, the first leg with microprocessor-controlled swing and stance phases. Buying the rights from the university, he traveled around the world to interest prosthetic manufacturers in his invention ("A Leg Up," by Isabelle Gallant, U of A Engineer, Spring 2011). However, he didn't receive any commercial interest until German manufacturer Ottobock bought the patent in 1992 and launched the groundbreaking technology.".

Then, based on work betweeen 1995 and 1998, a doctoral thesis at the ETH Zurich described an intelligently, microprocessor controlled knee for above knee prostheses built from available and affordable materials [1].

That research was performed 1995 to 1998, financially supported by Otto Bock, and Otto Bock presented its first C-Leg in 1997.

The rest is history. If ever there was a leap in performance of prosthetic function, ever, it was the C-Leg. No prosthetic hand ever came close to achieving this level of success.

So this particular doctoral thesis seems to contain some possibly interesting ingredients worthwhile looking at. As any doctoral thesis here is public record, and a copy of it must be made available at the public library, I borrowed a copy for further information.

There are some other prosthetic developments, however, nowhere else is academic research anywhere near that successful as in the instance of the C-leg:

  • Otto Bock Michelangelo hand; the mechanism seems to come from American DARPA or other army research and probably was just built, the first glove was a great design work. So there is no analytical approach comparable to the C-Leg. It is too heavy, it does not work with prosthetic gloves really, it is not sturdy.
  • i-Limb: This cannot possibly have suffered too much analytical thought. The device looks more like it was born out of something else. While it does not always function as maybe intended, it is really lovable. It does not have a reliable precision grip, it is really weak, it tears up its paper thin gloves within minutes.
  • TRS prosthetics: Bob Radocy as end-user himself developed by far the greatest useful solutions. But they are not the result of extensive academic efforts, so they cannot be compared to the C-Leg. They are extremely good though and any analysis must start there.
  • Toughware PRX: These devices are extremely well made, mechanics wise - but we lack an analytical model that precedes the engineering there as well, comparing this to the C-leg approach.
  • Becker Mechanical Hand: Also the Becker hand was clearly built by someone with great practical and pragmatic understanding. No analytical effort of the magnitude of a C-Leg preceded it though.
  • Hosmer hooks: they came out of a practical development, no scholarly work appeared to be prepared for these either.

 

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[1] D. Zlatnik, "Intelligently controlled above knee prosthesis," PhD Thesis, 1998.
[Bibtex]
@phdthesis{zlatnik1998intelligently,
  title={Intelligently controlled above knee prosthesis},
  author={Zlatnik, Daniel},
  year={1998},
 school={ETH Zuerich, Switzerland}
}

Toughware Equilux - new VO (voluntary opening) / VC (voluntary closing) body powered device - industrial grip pads [concept, beta]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Toughware Equilux - new VO (voluntary opening) / VC (voluntary closing) body powered device - industrial grip pads [concept, beta]; published August 17, 2017, 20:15; URL: https://www.swisswuff.ch/tech/?p=7569.

BibTeX: @MISC{schweitzer_wolf_1574228481, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Toughware Equilux - new VO (voluntary opening) / VC (voluntary closing) body powered device - industrial grip pads [concept, beta]}}, month = {August},year = {2017}, url = {https://www.swisswuff.ch/tech/?p=7569}}


Read about the Toughware Equilux here. All prosthetic hooks, prehensors or grippers lack the option of using industrial grip pads. Pads that are readily available, cheap, durable and that the user can easily switch.

And grip pads and grip gloves are a real issue. As posted before, grip pads must be soft,  possible to clean, easy and cheap to replace and convenient. These requirements are in part mutually exclusive. With the knife holding issue of the Equilux, what easier than to mount some standard bike rim brake pads and take it from there.

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#userdrivendesign Prosthetic arm design: i-Limb Revolution versus customized body powered arm in a work environment combining bodily exertion, wide temperature ranges, wide body motion ranges, heavy workload and subtle grips [Cybathlon Symposium, Oct 6 2016, Poster A12]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - #userdrivendesign Prosthetic arm design: i-Limb Revolution versus customized body powered arm in a work environment combining bodily exertion, wide temperature ranges, wide body motion ranges, heavy workload and subtle grips [Cybathlon Symposium, Oct 6 2016, Poster A12]; published October 2, 2016, 13:05; URL: https://www.swisswuff.ch/tech/?p=6342.

BibTeX: @MISC{schweitzer_wolf_1574228481, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - #userdrivendesign Prosthetic arm design: i-Limb Revolution versus customized body powered arm in a work environment combining bodily exertion, wide temperature ranges, wide body motion ranges, heavy workload and subtle grips [Cybathlon Symposium, Oct 6 2016, Poster A12]}}, month = {October},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=6342}}


PDF of poster presentation @ Cybathlon Symposium Oct 06 2016 @ Kloten.

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UNYQ company offering ready-to-order design customization for leg prostheses [new products out]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - UNYQ company offering ready-to-order design customization for leg prostheses [new products out]; published May 11, 2014, 21:36; URL: https://www.swisswuff.ch/tech/?p=3019.

BibTeX: @MISC{schweitzer_wolf_1574228481, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - UNYQ company offering ready-to-order design customization for leg prostheses [new products out]}}, month = {May},year = {2014}, url = {https://www.swisswuff.ch/tech/?p=3019}}


The Californian charge towards anything a 3D printer can print now caused UNYQ to open. Weird thing, nothing about this on the website of Fastcompany - usually early to publish what "really" is going on.

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Prosthetic device research - what to aim for [go for it!]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Prosthetic device research - what to aim for [go for it!]; published November 27, 2013, 13:58; URL: https://www.swisswuff.ch/tech/?p=2491.

BibTeX: @MISC{schweitzer_wolf_1574228481, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Prosthetic device research - what to aim for [go for it!]}}, month = {November},year = {2013}, url = {https://www.swisswuff.ch/tech/?p=2491}}


1 Comment

As we look back on decades of what appear to be functionally not too successful academic research into the construction of prosthetic arms, we can conclude that it is now the time to read them the riot act:

  • socket and suspension technology still is a myth for academic researchers; industrial developments are the only advancement that is notable in this domain [1];
  • mechanical wrist units and cable setups are the main problems affecting heavy duty task performers with their prosthetic arms; there is virtually no research done here whatsoever;
  • gripper, hand and hook shape is mostly not determined by any recent concise grip shape analysis or research that was done in that direction; if anything, most designs are probably the result of tinkering, experience and practical thinking;
  • myoelectric arms - anything that is commercially available - still operate with two electrodes, just as the Russian Arm did, so absolutely no advancement in over 70 years now, and
  • the same problems that affected the Carnes arm after 1908 (i.e., impressive appearance, circus style propaganda, everyday usefulness very limited, insanely overpriced) also affects modern "bionic" prosthetic hands.

So it is fair to say that...:

  • academic research into construction of prosthetic arms or hands has one systematical outcome (with a very few exceptions): it does systematically fail the users inasmuch as actually available prosthetic arms or hands are concerned; if however industry based research or tinkering lead to current solutions that actually work, state funded research such as by the SNF (see projects here) or NIH (projects here) should consider pulling their funds from their notoriously well known non-developer projects (i.e., not developing true answers to true questions) and direct their funds towards more appropriate work that actually deserves the title "prosthetic arm/hand research" ;
  • researchers that look at prosthetic hands or arms (or pretend that they do) must be really bad chess players; why? Because in chess, if the opponent starts to block your important chess pieces (not so much pawns but the others) then if this slows you down in further chess play, you should treat that with a very high urgency while respecting game rules; so any "myoelectric" device producer that cannot sell their dead stock would have to revise socket technology, and if just simply out of self preservation, as that is the most relevant limiting issue for these types of arms. Instead, prosthetic part producers try to belittle users of body powered arms personally, they sell really badly manufactured parts to discourage body powered arms, and overall exhibit vivid indication of absent strategies that work within acceptable rules of conduct and behavior.

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[1] R. D. Alley, W. T. Williams III, M. J. Albuquerque, and D. E. Altobelli, "Prosthetic sockets stabilized by alternating areas of tissue compression and release," J Rehabil Res Dev, vol. 48, iss. 6, pp. 679-96, 2011.
[Bibtex]
@article{alley2011prosthetic,
  title={{Prosthetic sockets stabilized by alternating areas of tissue compression and release}},
  author={Alley, Randall D and Williams III, T Walley and Albuquerque, Matthew J and Altobelli, David E},
  journal={{J Rehabil Res Dev}},
  volume={48},
  number={6},
  pages={679--96},
  year={2011}
}

Plastic - can be sprayed on as fabric [new material]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Plastic - can be sprayed on as fabric [new material]; published July 11, 2013, 11:51; URL: https://www.swisswuff.ch/tech/?p=1771.

BibTeX: @MISC{schweitzer_wolf_1574228481, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Plastic - can be sprayed on as fabric [new material]}}, month = {July},year = {2013}, url = {https://www.swisswuff.ch/tech/?p=1771}}


From Fabrican:

You spray it on.

Then there is fabric.

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Plastic --- heals [new material]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Plastic --- heals [new material]; published July 11, 2013, 11:35; URL: https://www.swisswuff.ch/tech/?p=1766.

BibTeX: @MISC{schweitzer_wolf_1574228481, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Plastic --- heals [new material]}}, month = {July},year = {2013}, url = {https://www.swisswuff.ch/tech/?p=1766}}


Prosthetic arms and hands have three problems:

- comfort and fit

- function and weight

- decay

Even a bare stump is better in terms of comfort, fit and decay - mostly. Skin heals, often all one has to do is wait a little.

But now, self healing polymers are out.

From Sciencemag:

Chemists, meanwhile, have become increasingly interested in "self-healing" polymers. This sounds like science fiction, but several research groups have produced plastics that can join their cut edges together when scientists heat them, shine a light on them, or even just hold the cut edges together. In 2008, researchers at ESPCI ParisTech showed that a specially designed rubber compound could recover its mechanical properties after being broken and healed repeatedly. Chemical engineer Zhenan Bao of Stanford University in Palo Alto, California, and her team combined these two concepts and explored the potential of self-healing polymers in epidermal electronics. However, all the self-healing polymers demonstrated to date had had very low bulk electrical conductivities and would have been little use in electrical sensors. Writing in Nature Nanotechnology, the researchers detail how they increased the conductivity of a self-healing polymer by incorporating nickel atoms, allowing electrons to "jump" between the metal atoms. The polymer is sensitive to applied forces like pressure and torsion (twisting) because such forces alter the distance between the nickel atoms, affecting the difficulty the electrons have jumping from one to the other and changing the electrical resistance of the polymer. To demonstrate that both the mechanical and the electrical properties of the material could be repeatedly restored to their original values after the material had been damaged and healed, the researchers cut the polymer completely through with a scalpel. After pressing the cut edges together gently for 15 seconds, the researchers found the sample went on to regain 98% of its original conductivity. And crucially, just like the ESPCI group's rubber compound, the Stanford team's polymer could be cut and healed over and over again. "I think it's kind of a breakthrough," says John J. Boland, a chemist at the CRANN nanoscience institute at Trinity College Dublin. "It's the first time that we've seen this combination of both mechanical and electrical self-healing." He is, however, skeptical about one point: "With a scalpel, you can very precisely cut the material without inducing significant local mechanical deformation around the wound." Failure due to mechanical tension, however, could stretch the material, producing significant scarring and preventing complete self-healing, he suspects. Now, Bao and her fellow researchers are working to make the polymer more like human skin. "I think it will be very interesting if we can make the self-healing skin elastic," she says, "because, while it's currently flexible, it's still not stretchable. That's definitely something we're moving towards for our next-generation self-healing skin."

Links:

Chinese farmer makes functional affordable prosthetic arms [amputee driven innovation]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Chinese farmer makes functional affordable prosthetic arms [amputee driven innovation]; published May 27, 2013, 04:42; URL: https://www.swisswuff.ch/tech/?p=1686.

BibTeX: @MISC{schweitzer_wolf_1574228481, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Chinese farmer makes functional affordable prosthetic arms [amputee driven innovation]}}, month = {May},year = {2013}, url = {https://www.swisswuff.ch/tech/?p=1686}}


The previously announced abandonment of any mechanical and body powered type of prosthetic arms and hands by major manufacturers has now found new suppliers.

It appears that on the planet that real workers live on (not the chee chee froo froo world where carbon yacht fan Max Näder reams insurances with Michelangelo ""bionic"" hands) amputees drive innovation - not Centri, Hosmer, RSL Steeper, Touch Bionics or Otto Bock. They would have mechanical drafts they could most easily use to build useful nice looking body powered hands. It is just not what they do. So that is where us amputees come in.

Latest video of a Chinese farmer. Very impressive.

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Hugh Herr and the rest of the world [phantasy talk, science fiction, hype]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Hugh Herr and the rest of the world [phantasy talk, science fiction, hype]; published August 28, 2011, 13:00; URL: https://www.swisswuff.ch/tech/?p=478.

BibTeX: @MISC{schweitzer_wolf_1574228481, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Hugh Herr and the rest of the world [phantasy talk, science fiction, hype]}}, month = {August},year = {2011}, url = {https://www.swisswuff.ch/tech/?p=478}}


Hugh Herr is a double leg amputee who comes up with new prosthetic designs that are out there in terms of manufacturing and selling to everybody - far too complex, far too expensive.

But great promises go along with them. From these, he and contemporary "bionic limb" representatives generate these utterly unrealistic trumpet-sound like promises that sound too good to be true and they are always the same.

If these hype aficionados restricted their trara to prosthetic legs it'd be alright as sooner or later they sure could advertise to build a 3000 horsepower leg system that propels people at jumbolino airplane speeds - but inasmuch as prosthetic arms are concerned, I take a personal interest (remember the title of the blog here that you clicksed on?).

So interestingly, i-Limbs and its likes also repeat to be mentioned - apparently a "bionic" hand is "bad ass" looking. Well, by the sound it is not bad-ass at all. It may be bad ass looking maybe to some people that never stopped playing with puppets, but entirely useless to do anything even remotely real bad-ass for everyone out there.

To merge man and machine, that was what part again that Hugh Herr wants to merge to the man? Yes that part? Ah, a "machine". Now, that's gotta actually be a machine in the very narrow sense of the word: a functional well designed, well engineered piece of engineering that actually functions (rather than just visually represents) to accomplish a task and to perform work. Let that melt on your tongue before moving on (we are talking about prosthetic hands and arms, right? remember the title of my blog?) - p-e-r-f-o-r-m  w-o-r-k.

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