Instructables
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Picture of Thumb Prosthesis
This is a high durability, high functionality low cost prosthesis for those missing the distal phalange of the thumb. This creative method can be extended to replace the distal or distal and middle phalange of any finger. The process detailed below is the greatest technological advance in prosthetics since the introduction of modern plastics, and will spark a revolution in the prosthetics industry.
 
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Step 1: Models

Picture of Models
I have included two models (free of restriction, share with all of humanity). You can use either model, the claw model is of more utility and can apply greater force than than a natural nail. You can also generate your own models from scratch OR (the most realistic and best fitting) generate a 3D scanned model from a whole digit scan and applying a mirror function to the model.

Step 2: Measurements

Picture of Measurements
Compare digits to find the specific metrics for scaling your model.

Step 3: Measurements

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Measure residual digit.1.jpg
Measure the residual digit (Residuum). Accurate multiple measurements will allow for a greater custom fit.

Step 4: Measurements

Picture of Measurements
Accuracy in measurement is paramount as this prosthesis relies on mechanical fit rather than flexible suction (restricts blood flow and thus wear time) fit.

Step 5: Scale Model

Picture of Scale Model
Adjust model to fit residuum metrics acquired above. This is accomplished with modeling software and scaling for length and diameter. Also one should scale areas radially along the vertical axis.

Step 6: Print

Picture of Print
PRINT. This prosthesis is most durable when printed in nylon. I suggest that one always use a human friendly plastic for anything contacting the skin. Taulman Nylon 645 is the best material that I found as it has superior strength and quality as well as meeting the EU's REACH standards for non toxicity. Currently there are no suitable FDA approved printing plastics, however that will soon change.

Step 7: Comparison

Picture of Comparison
Compare the printed prosthesis with existing whole digit.
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Columbian662 hours ago

I should say as well that while the models hold up they are wonderful to wear. It's hard to explain what a strong feeling of balance and utility they give me. I do notice that the surface of the 618 is pretty slippery, and I'm expecting that, as soon as it gets here on Wednesday, a couple coats of Plasti-dip will remedy that, and make the thumb even more useful.

Tim

Columbian662 hours ago

Thanks, Xi,

The layers in the models I got yesterday are coming apart after about an hour of wearing them. It seems that just a little lateral flexing does it. I sent my printer the latest specs you posted, and I'll double-check that he's using them and just printing a single layer.

Any recommendations you can make will be appreciated.

Tim

Xibalbawax (author) 21 hours ago

Tim, sorry I didnt get back sooner. Here are the specs for printing I used on my 2nd gen makerbot.

normal print speed or slower for better adhesion

print temp 245 this temp got the best layer adhesion

1 shell, 0% infill, minimum humidity and dry material

I am using wings3D its free, I had not used 3d software to any extent and learned it fairly quickly. I found you have to make a print then compare to residuum and adjust thats where the calipers come into play for fine tuning. Tip on the modeling old school, select cross sectional areas of the model and scale, so grab the knuckle section and shrink it a bit you can scale on the x and y independently, then when you get close on the model lay your residuum over the screen image and compare from multiple angles.

I found when printing multi shell the layers do separate a bit, the material is strong enough in single layer to work.

Columbian6621 hours ago

Xi:

The printer showed me several versions of his printouts, but we are finding it difficult to get one to fit securely and for the portion beyond my femaining knuckle to be the right size (that area of the prosthesis tends to be too wide).

I'm also finding that the layers separate with just a little flexing. Can you recommend a solution to this?

Lastly, can you recommend an inexpensive CAD software I could pick up to tweak your models? I spent some time learning 3D modeling software a couple of years ago and think I could build some basic proficiency in not too long.

Thank you.

Tim

Xibalbawax:

I'm going to my printer's tomorrow to try a couple of preliminary
prostheses he's printed, and I'm pretty excited. I have a few more questions
I hope you can answer.

Can you tell me what color or colors of dye you used to color
your prosthesis? Did you have to mix different colors to match your skin as
well as you did?

Do you know of any other way to color the unit besides dye?

Have you tried spray-painting them, and if so how did that
work?

My printer tells me the prostheses will be printed in two
layers. I don't quite understand why or how that is. Can you explain it to me?

You mention down below that I'll have to trim the base of
the prosthesis. Would this be a simple matter of a knife and sandpaper?

I'd like to send you photos of the units we print, if you'd
be interested. Is there a way we could communicate that's faster than this
blog?

Thank you again for the hope you've provided me.

Tim

Xi:

Your movable thumb-phalange prosthesis sounds fantastic! Please keep me up to date on your progress.

About coloring, I'm thinking that I don't want to try to make it blend in. I'm going to try to color it in ways that make it look cool. I forget if I mentioned it, but I'm picking up a couple of cans of spray-on Plasti-dip, and will see if I can apply a colored, tacky-rubbery coating to the thumb pad (the area that you normally would touch things with) that will also add a bit of a cushion to the prosthesis. I may be picking up some draft printouts today. Pretty exciting.

Xibalbawax (author) 3 days ago

dclark-craddock, I dont sell these pretty sure I could get in trouble with FDA AMA etc... . Check the thread here, if you have more questions feel free to ask.

Do you sell these? I recently cut my thumb off at the proximal end (nearest to my hand) but am getting surgery to extend it to about the distal knuckle. Would be nice to have the tip!
Xibalbawax (author) 5 days ago

Tim, also the finger does flex it replaces the distal phalange of a finger and it moves the tip like a regular finger does when the middle and proximal phalanges move. Its dynamic. I am working on a prototype that will replace my thumbs phalange with one that moves in a similar fashion. I will have that one up in the future, its way more complicated than the static thumb prosthesis. The dynamic thumb will be awesome, should be able to build in a tactile feed back into the structure. Tactile feed back can be incorporated into the static thumb as well, but again its pretty complicated and I have had to much luck. Any way thanks for the questions, anyone else in the same boat can read all these.

Xibalbawax (author) 5 days ago

Tim, I wear all day as the day goes on they get a little looser. I wear in public any time I go out, just for the psycological benefit. Same machine got me as well and no you dont forget that. When your printer gets going try the Taulman 618 and 645 nylons 645 is softer. Once you get a spare for testing they can be died to match skin color be real careful its easy to get them too dark I have light skin it would be alot easier if my skin was darker to color the prosthesis. Also I clean with soap and an electric toothbrush and rinse them with alcohol prior to putting them on, I partially fill with alcohol and put on as Dr. told me to treat residuum with alcohol, this kills two birds. I will get you more info on the dying and surface finish and once you get one i am sure you will find some appropriate customizations.

Xibalbawax:

I was just looking at your Finger Prosthesis. What is the purpose of all the cutouts and the sort of wraparound straps? Does this thing flex?

T

Columbian6612 days ago

Xi:

I'm working with a printer in Portland, and he's building a jig for doing a cellphone 3D scan of my unimproved thumb. I'm real optimistic that we'll come up with something good, and will let you know.

Sweating: yeah I traded deodorant for a daily shower many decades ago. I never liked the idea of clogging up my sweat glands either.

I'm probably going to print versions of both your straight thumb for bass and the slightly flexed one for piano. how they work in non-musical situations will be a matter of experimentation.

BTW, How often and how long do you wear yours? Is it an all-day, every day deal?

And FWIW, My left resid looks very much like your right-hand version. Did you do your like most guys do--with a table saw? That's where mine went. It's not an experience one forgets, is it? I hope I learned something from it--other than "don't stick your hand into a moving saw again."

T

Xibalbawax (author) 12 days ago

Tim, I havent really considered any sort of liner or vent holes. since the prosthetic is hollow through out moisture collects away from my residuum. I have some silicone one they dont ventilate at all, Dr. claims the skin eventually stops sweating but I really dont like that concept. Once you get one made you will see how they work and if it needs improvement for your particular injury. If you get a chance look at thingiverse use this link to see a few more designs I posted," http://www.thingiverse.com/xibalbawax/designs ".

Columbian6613 days ago

thanks, Xi.

Have you ever considered putting some holes in the area below the distal knuckle, for ventilation? Do you think lining the inside with a piece of some kind of open-weave fabric might cushion the residuum and offer some airlfow?

I suppose it comes down to a balance between stability and ventilation.

I'm very optimistic about this whole project, and I hope you know how much hope your work is offering. Thank you again for doing this.

Tim

Xibalbawax (author) 14 days ago

Tim, The model I posted can be altered with 3d software like wings3d. You can select various parts of the model and scale them to fit better. I dont have a high resolution scanner. To get a good fit I visually confirmed the model by comparing my residuum to the visual image of the model in the software, once it was close I printed one then made more adjustments with caliper measurements. It really depends on your software, I am using a very basic one. Having access to a printer is of great help as you will need to make a few to get the fit correct. I find that when printing it is best to have the machine settings set for hollow print single or double walled. As far as the rigidity of the material its fairly soft and should be so its flexible enough to deform while putting it on. One step I find useful is to put the prosthesis in water and heat to boiling for a few minute I include dye at this step, it both colors and softens the nylon. Print the model upright, this allow for a single pass on the model as it prints and leaves a smooth surface both inside and out, rough inside = irritated skin. When it comes of the printer you will have to remove the base and contour the bottom for a better fit. As far as a coating, I haven't tried any yet. I roughen the exterior of the prosthesis to remove some of the nylons slipperiness. I am planning to try a rubber coating on the outside in the near future. I would not recommend coating the inside because of the coating may not be skin friendly an will decrease the interior diameter making it harder to get a god fit. Feel free to ask more questions.

Columbian6615 days ago

Xibalbawax:

I've been figuring out how to make my prosthetic, and a thought occurred to me.

Since one of the things I want to do is to play piano, I've been concerned about hitting the keys with a hard piece of nylon. That would be annoyingly noisy and possibly damaging to the keys. It occurred to me that I could coat the prosthetic with something like Plasti-dip, the stuff people use to coat tool handles with a thin, rubbery coating. I also started wondering if it might be helpful to coat the inside of the prosthetic with that stuff, to cushion my thumb.

What so you think of these ideas?

Tim

Columbian6616 days ago

Xibalbawax:

For the past few days, I've been trying to get up to speed on all the details of how I would do this. The trickiest thing is the 3D scanning you mentioned.

Could you tell me in a little greater detail how I'd do this? How do I shoot the thumb; how do I turn those photos into a model, and how does that model modify the dimensions of your original model? For that matter, how would any caliper measurements I make be applied to the model?

Would a guy with a printer be able to do this?

Thank you again for your help.

Tim

Xibalbawax (author) 19 days ago

I have been using one of these for about 2 years ( and as far as I know the only) and it is a bit of a game changer. It will give you the extended rigid thumb and it protects the sensitive areas. Also as far as utility I can apply slightly more direct and lateral force with the prosthesis than I can with my organic thumb because there is no feeling and the force is transmitted to a large area on the residuum.The plastic is semi rigid and will need to be slightly smaller than the largest point on your residuum and will slide on with slight pressure. The fit will depend upon the geometry of the residuum, the closer you get the fit the less twisting or unwanted movement, also you may find that it gets looser as the day goes on. I find the nylon to be really skin friendly the only requirement is that the interior of the print be very smooth. As far as getting one of these made you will need to spend some time and a few prints to get everything fitted. The materials are available online or at 3D print places like shapeway, the nylon is from Taulman3d. If you can find a local maker group that's probably the best way to go, with the low cost of a 3D printer for this size its worth buying a printer to be able to make the prosthetics on demand (they do wear out with use after months to a year) and its a lot easier with getting a great fit.

Columbian6619 days ago

Thank you for posting this. I used to play piano and
saxophone until I lost the distal phalange of my left thumb. Now sax is
impossible and piano is a struggle. (Computer keyboarding isn't a lot of fun
either.)

Your design seems to offer a lot of hope, but I am pretty ignorant of the technology
involved and need to ask some questions.

How would I get the prosthesis
on and off if it doesn't stretch?

How securely does it grip my residuum?

Playing either instrument would generate a lot of pressure
perpendicular to the long axis of the thumb. Would the prosthesis shift as I do
this?

Do you have a source for the nylon 645, and do you know how
much of it I'd need and what it might cost?

How can I find a reliable print facility with the right
printer?

You mention that for the optimal fit someone could "generate a 3D scanned model from a whole
digit scan." I have no idea how one might do this. Can you please explain
for the uninitiated?

Would this also produce greater stability?

Would the prosthesis cause any rash, chafing or other damage
or injury to the skin beneath it?

Are there people already successfully using this design?

Sorry for my ignorance. But your invention looks like it could
produce a life-changing difference for me, and I'm ready to take a shot at it.
I just need to know the nuts and bolts of getting it done.

Thank you again for this great idea.

pythonus8 months ago

you should make it in a position as if you were grabbing something, also there is a rubbish filament that could give you better grip . Just thoughts on how could you improve it , But nice work !

Makinwine1 year ago
While I am fortunate to not have a need I am absolutely thrilled and impressed in the way that you took control of such a tragedy and have the resolve to not only make it better for yourself but for anyone and everyone. My hat is off to you
kyinrunner1 year ago
I lost to the 1st joint of my left index finger, is there anyway to do this without access to the technology?
Xibalbawax (author)  kyinrunner1 year ago
Check my finger prosthesis at thingiverse, you can use this to make a model for your injury and then send it for printing
Xibalbawax (author)  kyinrunner1 year ago
Yes there is. The mechanical finger ring at rcmenterprise.com offers a dynamic prosthetic device for your particular injury, however it has a much large cost. I have a new dynamic prosthetic designs that may work but it is not yet perfected. With this current design it is absolutely possible to make a prosthesis for replacing the distal phalange. You can create a design for your self and have it printed a 3D printing service like Shapeways, i.materialize or Sculpteo. I will endeavour to post another instructable regarding the creation of a finger prosthesis. I lost the first and second phalanges of my right index finger. In the process of designing a suitable finger prosthesis I have also found solutions for those missing the first phalange. I am wholly willing to help you with this, if you are willing to be a test subject and provide some feedback. Please be patient as this is a project under development.
nerd74731 year ago
intersting
so you were in the army; by your tattoo
wylekat1 year ago
You could turn the claw one into a stylus with some conductive threads and such...
Xibalbawax (author)  wylekat1 year ago
exactly, conductive paint perhaps
agis681 year ago
The grow of our intelligence has begun when we start use our thumbs. good job!
Xibalbawax (author)  agis681 year ago
Thanks, you are absolutely right the thumb is hugely important and perhaps one of the greatest features that defines humans.
What heat, speed, and other settings did you use to print taulman 645 on the replicator? I have the same material and a replicator 2.

I found this while looking for ideas on movement assistance, that is, fitting up parts that aid a weakened limb, not replace part of a damaged one. Awesome work by the way.

Thanks
Xibalbawax (author)  PaulMakesThings1 year ago
I used heat of 250 and print speed of 50mm feed 50mm. I tried all the variable but what seems most critical to a good print is the humidity of the material. Temp between 245-260 all worked well. I try to make sure that i print on low humidity days which are often in NM, that is until I get some sort of dryer.
That makes sense, because I got some nice prints when I first tried and then it stopped working, bubbling and steaming. I live in Wisconsin right by the lake so there's plenty of humidity in the summer. I'll try drying it in an oven and see if it works out better.
jarikcbol1 year ago
I think the claw prosthesis would be less creepy if it was plain white or something. being skin colored, it just looks like some weird mutation.
Xibalbawax (author)  jarikcbol1 year ago
It works great for operating remotes for tv and cable
Xibalbawax (author)  jarikcbol1 year ago
the nylon I used for this is naturally clear to white. It absolutely looks like a mutation and it is better than my original thumb for several applications.
chaotick1 year ago
Brilliant! I don't know anyone that would need this - but such a cool demo of 3d printing!
Xibalbawax (author)  chaotick1 year ago
Thanks
samalert1 year ago
This is one of the wow use of 3d printing. When things like these are invented it makes you feel good in heart. This was a lovely project !
Xibalbawax (author)  samalert1 year ago
thanks
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