Good afternoon.

And thanks for

coming out today as the said my final
presentation is titled consistency and

magnitude of pinch force involuntary
opening body powered terminal devices.

So roughly ninety thousand people in
the U.S. have lost an eye percs Tremonti

however less than half of those
choose to utilize a prosthesis.

Of those users only
about ninety percent or

about ninety percent of that group
use body powered prostheses.

And body powered simply allows
you to control the prosthesis

with your own body motions as you
can see there in the figures.

There's a control cable
attached to a harness.

Which transmits those body motions
to the terminal device at the end

of the prosthesis.

This terminal device set serves as a very
crude replacement of the original hand and

a very common design is a split of
design which was invented by D.W.

Dorrance back in the eight
hundred ninety S. And

it's the most widely used type
of terminal device today.

It's a voluntary opening type of a device
which means that it's closed at rest and

as you put tension on that cable or effort
by the user you can open the device and

then the pinch force on the flip
side is provided by an elastic or

spring component.

Now put force or preemption force can be
determined by the number of elastics or

Springs used the magnitude is
constant because of this fact and

therefore once you have a set number of
rubber bands or whatever on your hook.

You can quickly adjust this amount
of force for particularly heavy or

fragile objects.

Unfortunately usually you have to choose
a force that's greater than what you

would use for your A.T.L. zx.

And this tends to be an efficient for
many amputees causing extra effort

from the shoulder joint
now rubber bands are the.

It's widely used type of
prehensile component.

These have been around for a long time.

You can see on the crab there the top they
were kind of taken from that idea and

just resize to fit this channel
on these terminal devices.

Now standard sizes
the the keener pale crepe.

That's seven eighths inch by
thirteen sixteenth's of an inch.

They do manufacture testing of these bands
including to strength breaking point and

ultimately long.

However they don't do any application
testing of these bands which is

interesting since they've been used for
so long.

Down at the bottom there you can see
an advertisement from house which is

one distributor of these claims that each
band applies approximately a pound and

a half of prevention which would lead you
to believe that there's this constant

increase that you're getting
a newer development.

Are these elastomeric rings that
are basically modified O.-Ring.

The variety on the top left
that you see was developed by

Pat hall at fluid seal Inc.

Up in Vancouver.

It was originally developed for Dr Bell
applications including roller conveyors

for packing industry things like that.

It's chosen for its very high
tariff strength as well as its

high rebound memory
the size you can see there.

These also have not had any application
testing done specifically for this use.

The part number is there because
the one that I'm testing is

not a commercially available product yet

and the bottom right you see another
figure from the husband catalog

claiming that these provide fifty percent
greater force than with the rubber bands.

So my purpose was to was
threefold to determine

if the prosthetic rings are an appropriate
alternative to these bands.

Secondly to develop an instrument which
can measure and record pence forces and

angles simultaneously through
the entire range of opening.

And also to produce and
evaluate force vs Angle graphs for

the various terminal devices.

Now might have prophecies were
also three fold the first being

that the force measurements will show
statistically significant differences

in the trends between the band trials and
the ring trials.

Secondly the incremental increase in
pension force with the addition of these

will vary significantly from
the manufacturer's claims

that I just showed you.

And thirdly a simple modification of
the hook terminal devices channel wit.

Where these bands are actually
sitting can significantly

increase the pension force
produced now in the past.

These are some of the measurement
tools that we've seen.

Used instead in these terminal devices.

Typically these are static analysis
where you have to set these devices

at certain angles so
using fish scales as you can see there or

something a little more sophisticated
like a curved beam force transducer.

With bolts for
getting different opening angle openings.

These people are able to measure punch
forces but again it's in a static state.

So.

My design I have named the pen
force pro affectionately.

As you can see if you will tilt your
head ninety degrees to the left

with a reply that.

It can see it can cycle these through
their full range of motion and

it's measuring as these
are the moving live.

So here's the instrument design and

measures French forces through
the entire range zero the sixty degrees.

Adjustable to all sizes and
styles of split hooks.

But they must be left.

Unfortunately I made
one part of it just and

too short to be able to
test the right handed.

But that's OK and it works by
measuring the tangential force or

the force with the force gauge held
at a perpendicular ninety degrees

to the pinching surface at all
times through that range of motion.

So my subjects out of all the books
available what you can see there.

Quite a variety.

I chose four for
health they split split votes.

Better come commercially available

from left to right there the house
more number eight X. five X.

A and the number seven workbook and on
the right is the out of box two load hook.

These all have they don't all have but
there are two different materials or

stainless steel and aluminum being tested.

There are different sizes and

there are different styles including
different levels of Cook can't which is

basically a tilt of the hooks
fingers which will show you.

I did five trials for each condition.

So I called them through the entire range
of motion at a controlled speed and

recorded forces and angles.

While doing so
the test conditions included

the out of Bach to load hook at its
highest load the number eight X.

hook with one through ten bands as
well as one through five rings.

Then I did the eight X. five X.
eight and seven with one three and

five bands after determining kind
of the force ranges those produced.

And then the same hooks with one in three
rings and finally a modified version of

the eight X. book with one and
three rings just as a proof of concept.

So these were preliminary results.

You can kind of get an idea here.

Of how these things are performing so
at the top one thing to note.

You can get the same
force with five rings as

you're getting with ten bands these
are both eclipsing the twenty lb mark.

This is significant for one because the
rings are a good deal easier to get on and

off of the hook and for two it's taken
half as many to actually produce the same

pitch for so that's going to be
something convenient for amputees.

Another thing to note is here.

At the one vs one one band in one
ring perform almost identically in

this case which is interesting paired up.

Another way to look at it is
the force production trends for

both rings and
bands separately you can see that the.

Show a much steeper climb towards
this twenty pound bench mark.

Where is the bands as
a slower progression.

So clearly just another way
to show that fewer rings

can achieve the same thing as bands and
that it also illustrates this compounding

factor with where the rings
are stacked upon one another.

So some more results looking at
the range of the different hooks

is very interesting because you can
note that just between bands and rings.

There's quite a difference in
the way that these are performing.

I used the out about to load as kind of
the control through here it's ideally

supposed to have the most linear type
of a curve because it uses springs.

It should constantly develop more
punch force as you open it wider.

However these don't exhibit
the same behavior and

it's interesting
particularly that eight X.

with three rings out performs all of these
in the rings and the area where I was

the same eight X. with the bands
is kind of in the middle so.

That leaves you to wonder what is
the difference between how these

are performed.

Finally what I did was a simple
hook modification using happened.

Vinyl tubing cut into one point eight
centimeter tall segments over here.

I also use electrical tape which as we
know can fix everything and using this

technique you can expand the total channel
with by seven millimeters increasing

it from thirty one three four to thirty
eight point three four zero meters.

So the results of this
were pretty exciting.

You see that you are getting over two and

a half times this the force
in the One Ring case.

As you were wondering without the
modification in the three ring case it's

the same trend where now eclipse in
the twenty lb mark with just three rings.

So this is another alternative for
addressing by.

Both for amputees they don't want
to deal with changing bands or

rings quite a lot or have to pile
bunch of them on their Additionally

you can address some of the gaps
between potential pitch for

savings by using a simple modification if
you needed just a pound more grip or so.

You may be able to achieve that
just by widening your channel.

So my acknowledgments I like to
think way higher first spending

countless hours responding to emails and
listening to me cry.

Mary hell for.

Giving me the idea and
he was the patient but

I showed pictures of actually
wearing those rings.

Jason that would John jars and
Steve's free go for

helping me with fabrication and
with troubleshooting Scott centers for

helping with soldering my research advisor
Gaiser gave up for all of his help.

I actually heard for
help with crunching numbers and

Rob McDonald for various troubleshooting
and helping me fix things when they broke.

My references and any questions.

Thank you.

That was because in the set up there
was not enough room to flip it down to

the low load and
also I don't know if that would be.

Really significant basically
the only reason I wanted it was to

show that linear.

Correlation as it opened and
how that differed it compared

to elastic cases I wasn't really
sure that the low load would be

clear enough because I was also getting
some interference due to vibrations and

things I wasn't sure that it would
illustrate exactly what I was trying to

get across that but
also just the machine when it.

Right well.

My personal experience I can
attest with bloody knuckles.

That getting these things on with the
applicator provided is a big hassle but

usually a screwdriver actually works best.

Or if you're by lateral you
might have another split hook

that you can use that would make it
easier but in terms of donning and

doffing the Rings I found significantly
easier because of the fact they roll

can roll them up to that lip and then
just use something to wedge them over it.

Whereas the bands they tend to stick and
grab to everything that they're touching.

And just the fact that there
are more surface area.

It makes it an inherent problem.

Like this

really risk factor.

Exactly.

Yet mathematically.

And essentially.

It's just.

As far as how they're laid and
they're well that that

I will get into a little bit more and
I'm glad that US but it's here.

Pretty sure I've got
a slide on this somewhere.

So you can kind of see.

In this illustration how the bands

kind of tend to bunch up and along

with that kind of causing variation in the
force production it also causes these to

get little micro fractures all over them
so they cause them to tear down quickly.

This isn't the best picture but this is
a hook with ten rubber bands on it and

you can see that they're kind of
exceeding the width of the channel.

So that's where you can do
a big tend to get sloppy if you

see a prosthetic user out in.

In daily living.

Typically if they're putting more than ten
bands on those bands are everywhere there

on their wrist practically.

They're overlapping they were
going all over the place so

that was something I tried to control
simply by lining up all the edges

on the distal part to try to line up those
edges and make sure that none of them

were coming over this way some of them
would bunch up on the thumb there.

But that was my best way
of controlling was just

trying to be very meticulous
with I applied them.

But when you first close is right.

Certainly and that's I think
an inherent problem with these bands is

that when they're stacked on each other.

The fact that they're flat
objects being stacked and

that they have elastic properties
the most outer one tends to spread more

third stretch more therefore it's kind of
like a tug of war where you have one guy

kind of providing most of the force the
guys underneath are being compressed and

they're not able to fulfill
their their full potential.

It's just.

There's just we're just well

that was my original intent as kind of a
pilot study was to do something like that.

What didn't happen because we weren't
sure if we would have time we wanted

to test them to failure.

So I'm not exactly sure how they compare
I tried to get the manufacturers and

from ation you can get them for
the Benz as far as you can see they're

there long percentage in terms of how many
times their size they will stretch and

how many repetitions they'll tolerate.

But I don't have a comparison
of those to the Rings at this

time which would be helpful.

It's just material.

Information.

It's anything else.

Chris.

Actually.

You get your own side.

Go ahead.

Right.

Well basically.

As I mentioned I kind of wanted.

Basically a variety of sizes and styles.

There are a lot of things
that vary about these hooks

some of them are liar
shape as you can see here.

Some of them have canted
fingers which means it's angle

of the actual pinching surface.

So those are all things that I
had to kind of take account and

design in the machine to be able to
test them all consistently I chose

these this one is stainless steel This
is aluminum aluminum stainless steel.

So they've got different material
properties I was hoping that maybe they

would exhibit some differences which I
think that may account for the the one

graph that I showed you that showed
variability between the different devices.

I think that actually some energy
absorption occurs in the softer metals

potentially which is an exponent
possible explanation for

why there's not as much force being
transferred up to the Pentagon surface.

So from the point where those
elastics are applied here.

So I wanted a variety of materials I
wanted a variety of links with and

canted fingers just basically for
testing range and

this out about Cook as I mentioned since
it uses springs as opposed to elastic

I thought that it would be a very good
visual of a linear relationship there

as the springs constantly increase
their tension as they're spread.

I thought of that would be interesting to
see because these obviously they wear out.

They lose their memory and

so there's going to be a drop
off effect seen on those curves.

Between.

Between each trial eyes
would switch them out so

they are fresh one between each condition.

I would trust them switch them out.

So they were always fresh and they had a
minute to rest in between each cycling so

that when they weren't changed like for

the one one ring case it would be tested
then to be allowed to rest kind of read

retain its original memory and
then be done again so that way.

There was no or hopefully a minimal
heating up of the material and.

Lots of that memory.

Use the last six years.

It's certainly.

Well as I kind of mentioned if we go back.

You can see obviously there are gaps
that aren't being addressed here for

print force options and

I don't graph all of the bands and
rings but even with them all up there.

There are some areas that
are significantly significantly gaps.

So you had a user that needed a very
specific amount of pension for

say she's likes to knit or
something like that and.

Has trouble holding on
to the needle you could

incrementally add using various widths of
this material these were three layers.

To get seven millimeters to
three layers in each channel.

So you could do two or one and

just get a minimal increase that
would kind of address those gaps and

allow people to have more options of pent
forces may not mean really necessary but

especially in cases where
an amputee can't keep tension on

that cable to keep from crushing
a styrofoam cup or something like that.

You could go down.

It's maybe one band's not quite enough but

one band with a one millimeter
increase might be perfect.

So it's just another option that
hadn't really been explored and

I wanted to do it as a proof of concept.

Kevin.

Well one thing that I did
look at I tried to be

good about documenting so like in this
case this was with the modification and

you can see those rings being around
of the definitely tend to migrate

more than the bands obviously because
they can roll so I did one iteration with

the zip ties to keep them from moving
That was one attempt at controlling it.

But obviously those essentially anchor
points are what are produced in the force.

So if the thing is moving band or rain.

You're going to lose force
as it slides Proxima way.

So I tried to be attentive in the way

that I played the bands as I was
saying and then in the ring scenarios.

One reason I have prophesies that the One
Ring versus one band were so similar.

Is that that ring provides greater
force but when it rolls down onto

the proximal aspect of that it's
not using its full potential.

So that makes it more closely resemble
the band's performance in the one vs

one scenario.

That answer.

Yes through.

The right.

As close as.

The voluntary close design
as opposed to what I study.

Yeah.

The main benefit to that story
this of randoms the main benefit.

To using a voluntary close
device especially for

pediatrics it's easier
to learn you get more of

a opprobrious Cept of feedback type of
response because as you close down.

You're feeling the resistance of whatever.

You're grabbing so it's more like
your natural approach to sizing and

grip grabbing down on something one
issue with that is that you have

to maintain that tension to hold on
to something so really the inherent

benefit to voluntary open that I'm
starting is that you can be relaxed and

it's going to hold on
to whatever you need.

So it's definitely.

Nice for people that use like big work
hooks people that are doing heavy lifting

to be able like in the case of the
modified with three rings you can get very

high force with just minimal amount of
rings that's handy because they can

carry around whatever they need
with up and putting forth.

Whereas in a voluntary close
they'd be holding it and

you can't you can only produce.

The force you can produce is directly
a function of how hard you can push.

So that's when the patient and
that is I think it.

OK thank you very much thang.