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Category: Material science

Embodiment of a prosthetic arm [reflections, thoughts, considerations]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Embodiment of a prosthetic arm [reflections, thoughts, considerations]; published September 16, 2018, 15:42; URL: https://www.swisswuff.ch/tech/?p=8513.

BibTeX: @MISC{schweitzer_wolf_1569172416, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Embodiment of a prosthetic arm [reflections, thoughts, considerations]}}, month = {September},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8513}}


So, apparently I had been "identified" as a "super prosthesis user" by a group of researchers. And I was invited to talk about embodiment in context of the "rubber hand illusion" at a user interface or robotic control workshop [link].

So is that what I am: a "user"?

Tsk.

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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_1569172416, 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_1569172416, 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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Grip performance enhancement through modifying terminal device gripper surface [overview]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Grip performance enhancement through modifying terminal device gripper surface [overview]; published July 19, 2017, 16:00; URL: https://www.swisswuff.ch/tech/?p=7431.

BibTeX: @MISC{schweitzer_wolf_1569172416, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Grip performance enhancement through modifying terminal device gripper surface [overview]}}, month = {July},year = {2017}, url = {https://www.swisswuff.ch/tech/?p=7431}}


When using a prosthetic arm with a terminal device, grip performance is a key issue.

Usually, a bare steel hook such as the Hosmer model 5 works through just about every situation. That is just because that is how it is. A closer look reveals, however, that that view may be overly simplistic. If anything, it requires explanation.

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Trautmann hook [3D printed steel parts, assembly, first use]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Trautmann hook [3D printed steel parts, assembly, first use]; published December 28, 2016, 17:53; URL: https://www.swisswuff.ch/tech/?p=7037.

BibTeX: @MISC{schweitzer_wolf_1569172416, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Trautmann hook [3D printed steel parts, assembly, first use]}}, month = {December},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=7037}}


First, I had performed a feasibility test using a PLA model that I had printed myself to see whether I really wanted a Trautman hook. After that, I had decided that I wanted one.

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Graphene-based neural interfaces are a first promising method to interfacing directly with our nerves [science]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Graphene-based neural interfaces are a first promising method to interfacing directly with our nerves [science]; published February 26, 2016, 15:41; URL: https://www.swisswuff.ch/tech/?p=5712.

BibTeX: @MISC{schweitzer_wolf_1569172416, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Graphene-based neural interfaces are a first promising method to interfacing directly with our nerves [science]}}, month = {February},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=5712}}


From [1]:

Connecting technical conductive materials - as in: wires - to nerve cells - as in: spine, brain, peripheral nerves - is important to develop prosthetic devices where interfacing surfaces should only minimally disturb the nerve cells and surrounding tissues.

starwarshand

Current materials are tungsten microwire electrodes or silicone based electrode arrays that represent a long-term trauma and that elicit a long-term inflammation. Typical long-term issues are the formation of an insulating tissue layer around the implanted electrodes, the so-called "glial scar". Not only is the glial scar with concomitant long term inflammation a health issue per se, also the SNR (signal-to-noise ratio) deteriorates until the electrode entirely fails.

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[1] A. Fabbro, D. Scaini, V. Leon, E. Vázquez, G. Cellot, G. Privitera, L. Lombardi, F. Torrisi, F. Tomarchio, F. Bonaccorso, and others, "Graphene-Based Interfaces do not Alter Target Nerve Cells," ACS nano, 2015.
[Bibtex]
@article{fabbro2015graphene,
  title={Graphene-Based Interfaces do not Alter Target Nerve Cells},
  author={Fabbro, Alessandra and Scaini, Denis and Leon, Veronica and V{\'a}zquez, Ester and Cellot, Giada and Privitera, Giulia and Lombardi, Lucia and Torrisi, Felice and Tomarchio, Flavia and Bonaccorso, Francesco and others},
  journal={ACS nano},
  year={2015},
  publisher={ACS Publications}
}

Body powered arms [technical design overview]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Body powered arms [technical design overview]; published November 21, 2013, 07:05; URL: https://www.swisswuff.ch/tech/?p=2371.

BibTeX: @MISC{schweitzer_wolf_1569172416, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Body powered arms [technical design overview]}}, month = {November},year = {2013}, url = {https://www.swisswuff.ch/tech/?p=2371}}


Body powered arms are not the same. Despite everyone saying they understand what these are, these arms are not the same.

My setup explained, a generic setup explained. To show similarities and differences. For those in need to learn about this, technical differences to myoelectric arms are explained.

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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_1569172416, 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_1569172416, 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."

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