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Okay, well it seems like the flow traffic has slowed down a bit so we’ll try to let people in as they join. If you know somebody who isn’t able to be here right now we’ll still let them in as they come.
So anyways I’ll get us started. Thank you all for attending our presentation. We are team socket here. It’s myself, Matt Walsh, we have Aaron Weeks, Preston and Garrett with us and we are tasked with building a better prosthetic. So we met with advanced orthotics and prosthetics here in Boise Idaho and met with a clinical prosthetician in order to solve a problem that many lower leg amputees have. Now there’s over 1 million lower leg amputees living currently in the US and each of them has to have a custom fit prosthetic. This often involves going to one of these prosthetic fitting places, having a mold made of their leg, and then a custom making sure that their leg will fit them. As you can imagine after a amputation their lower leg is very sensitive. The clinician needs to make sure that the correct pressure points are surrounding the leg because any poor fit can really damage the person’s leg. Even after they get their prosthetic fit the first time many many people will often have to accommodate for vole change throughout the day. Now their leg is not a static object when they wake up in the morning and they start moving around, based on their activity and diet their leg usually tends to decrease in vole as they get moving. And this decrease of volume creates a small vacuum or small void in their prosthetic that if that isn’t accommodated before it leads to issues inside this prosthetic. This can be anywhere from minor rashes, bruising, bleeding, even loss of balance. Many amputees don’t even trust their leg anymore if it’s such a poor fit.
Our team is tasked to solve this issue and currently there is no prosthetic on the market that can automatically detect when it’s a bad fit and and do something to to adjust for it. Now our project it’s a biomedical device and biomedical devices the first and foremost have to be safe to use. This is going to be something that the amputee is using every single day of their life it has to be, it can’t hurt them at all and they should be able to use it without too much learning. Our goal is to increase their quality of life.
Currently amputees will need to take off their prosthetic maybe once or twice a day and add between 1 to 11 socks over their stump to accommodate for that volume change. As you can imagine this is very intrusive to their day of life when they often have to go and find a private area to change out their leg. Many people don’t even care to do that because it’s such a strain on their their way of life. But if they don’t do that their leg gets hurt, yeah. So our goal is to make something that prevents them from having to disengage from their lifestyle and continue on with their day.
And so the first step of this process was determining what’s already on the market. Right here you see the new flex silicone prosthetic socket. And so what this is it’s a silicone liner that the user will slip their residual limb into, and as they slip it in, it forces the air out of the one-way valve you see at the bottom of the device. This wall has a lot of pros that go along with it such as it does fill the void or it does compensate for the vole decrease seen by the user throughout the day. But these these silicone liners can be very harmful to the skin because post amputation it leaves the skin on the residual limb in a very poor condition allowing for an increased risk of damage as Matt spoke on before.
The next device that we took a look at was the… it was a more manually adjusting tightening system. And on the right you see the boa tightening system. And the idea behind this one is the prostitution that would make this device will pick out specific pressure points on the user’s leg in which panels are able to tighten around and direct pressure accordingly. This does have its list of pros. It’s easily adjustable by the user and it allows for the pressure to be directed to those specific points but it does have its its downfalls where if the user does not adjust the prosthetic in time it can lead to a poor fit prosthetic and it can lead to injury of the residual limb. So our design hopes to change that.
So what we have here is our initial conceptions of our current design. On the left you can see a simple drawing sketch of that. We have the socket with the three tightening panels and we’re using an arduino micro controller. And we’re getting input from three sensors placed on those tightening panels and that data will allow it to control the the motor that you see there on the left side of the drawing, and automatically adjust
the tightness in response too, if it’s getting too loose or too tight.
So what we use, we have three force sensing resistors. We’ve got in our arduino microcontroller. We’re using a 12 volt worm gear DC motor. The worm gear prevents it from back driving so you can’t loosen it by pushing on it too much. We’ve got a spool on the motor for the the cord to wind around. We 3D printed that. And we’re using a steel cable, just allowed us to feed it through the prosthetic better when we’re assembling. And what we did – what we found is that those sensors that we have, they’re a variable resistor based on how much force is being put on them but it is not linear with the amount of force which makes it very difficult to actually directly correlate the amount of force being put on them with the amount of pressure being exerted on the leg from the prosthetic. So what we’ve done is we’ve essentially created a – if you’re familiar with like the sleep number beds you’ve got your your perfect sleep number, your comfort setting. We’ve essentially created something like this which allows you to dial in on the the fit that’s right for you because it does vary significantly from person to person. And it will target a narrow range of tightness unique for the user and it will automatically adjust whenever it strays outside of that range. Just another basic picture of some of our circuitry.
So one piece of design of this project that had to go through many iterations was the spool. As you can see on the left we have our first design there and then the final design. And we have a number of issues with this piece because the spec sheet that was provided from the manufacturing the factor was incorrect and it led to improper fitment of the pulley and so it took a few different iterations to dial in the correct dimensions and once we eventually found them we were using the pulley and as you can see on the right I put a little arrow pointing at where the pulley ended up failing. Essentially the shaft of the motor ended up crushing the hub of the spool and led to the pull out the school mill no longer working. This was then rectified by upping the infill of the spool itself to 100 percent and we ended up getting much better results. During our testing process we were able to suspend 86 pounds from the device. We did this by clamping the motor down and periodically increasing the weights and as we increase the weight we were looking for something to fail and so it was either going to be the cable, the spool, or the motor itself. And eventually we figured out that the failure was in the spool. The hub crushed eventually and we identified the spool as the weak point of the device.
So moving on, we eventually concluded that testing would, we would use a blood pressure cuff, a sigma nominometer to model a residual limb by filling and deflating it. It models the volume fluctuations of about three to eleven percent seen by most amputees throughout their day. And we tested our system to failure as was noted by Garrett. And the critical failure point was that spool which is probably a good thing because it’s not going to harm the user when that finally fails. It’s not going to shock them or anything.
And so what we got from our testing, this is our first graph. And it shows the pressure being read by each resistor (we had three of them) as the tightness of the device was increased. And what this really shows is that each resistor is receiving approximately the same amount of pressure and in our code we have it set up to notify us if there’s an extreme outlier or if there’s a potential malfunction where one resistor loses connection to the arduino and it stops reading entirely or it just goes off the charts and thinks that it’s getting way more pressure than it is and there’s a red flag that’ll be set off in our code for that.
And this graph here shows a second test of about 90 seconds with our air bladder and in this we let the pressure of the sphygmomanometer decrease over time and you can see each of those drops in the graph is when we reduced the pressure in our blood pressure cuff. And the reaction is our arduino and our motor tightening it back up to within that acceptable range of tightness that is set by our user. For our purposes we just set it for a value. But we can see that we’re getting the proper reactions that we’re looking for and that’s really reassuring for our project. And that brings us to moving forward in the future if we were to continue on with our project and have more time we would like to be able to conduct some human testing of our device and that would provide more succinct and specific feedback about things that we might not have been able to consider so far and how to implement those ideas. Additionally we need to find a way of internalizing and integrating our components of our system so that we can waterproof a compartment to meet safety standards. And this integration would also ideally make the whole device mobile because right now it’s a bunch of wires and cords and can’t move very easily but we have a couple ideas for how we can move forward with that. And by shielding the critical components in its own kind of isolated spot it protects it from outside elements which increases its durability as well. And the the last part that’s on our radar right now at this point is finding an improved power source with a long lasting battery life that’s also rechargeable because the idea of our project is to reduce the interaction with the device required by the user. And if we can find a longer lasting battery life that means that our goal of automation and minimum disruption to the user is furthered along.
And that brings us to if you guys have any questions.
Nice work guys. I’m Kevin Faulk and I taught there about four or five years in the freshman service learning class and I’m an amputee of 13 years. And so I miss working with you guys. I know this year has been different stuff but I would like to be a part if you guys do continue on because I do have a lot of hands-on experience of being an amputee and I’ve even worked for a prosthetic company that has designed limbs similar to your sockets to yours. So yeah, if you want to move forward get in touch with me or Amy and I’ll be glad to be the guinea pig and participate and help you guys out. But great job so far!
Thank you. Thank you. We really appreciate that feedback.
One question I do have, I know it’s based on pressure because I deal with pressure every day and I woke up this morning. I tell people I don’t put my leg on until 10 o’clock. I kind of wait around. I put it on, I put it on about noon today but by the time I put it on and it’s swollen up some more. And I just, there’s a lot of temperature changes too that affect my leg and the swelling and stuff. Does this device have some sort of, is it automatic adjustment or does a user have the adjustment to dial something in? Let’s say I’m hiking up table rock for an event and it’s getting more pressure on it. Can I adjust it down or adjust up as I go up the table rock or down table rock because there’s that capability?
Uh yeah, right now we have it, it’s set up to run both ways. So if it’s too loose it’s going to tighten up but also if the pressure is increasing too much it’s going to loosen to accommodate for that.
How quick is it? Does it sense it right away or is it a minute or two?
Well you can see on…
I saw your graph it looked pretty quick.
Yeah it really was. Let me back up here to that one right there. You know that this whole thing is over the course of 90 seconds so the dips are where we released the pressure and it climbed back up within just a couple of seconds to compensate for that.
When putting on a socket or taking the socket off does it expand? Let’s say first thing when you put it on and it’s sitting there and it’s wide open? And then does it do it again? Because I’m just curious. Because I have to, I push, I have the release valve by the little push button on mine and I force it in and I do a lot of pushing when I push it on and then by the end of the day it is stuck on there really pretty good. And I’m sitting there putting my foot down and pulling it off so I’m just curious. Does it have that on and off capability of releasing pressure?
Uh yeah, we do have, we haven’t completely integrated it into the physical project yet but we have, we have the design for basically a kill switch. So even in the event that it malfunctions and it’s getting too tight or if you’re just ready to take it off, some sort of button or switch that will cause it to just completely expand to where you can just slide it off.
Okay.
And we got some in the chat.
Uh yes, I’ll read the first question from the engineering studio. How feasible would it be to add tiered pressure ranges to your control system? I am going to assume you mean tiered pressure ranges as in, I’m going to be going on a run so I wanted to be at this pressure or I’m just walking around the house I’m at this pressure. And that’s definitely one of the next steps we want to take. When Preston was mentioning we want to have a little bit of human testing because as you guys can see from this graph, it responds fairly instantaneous to any pressure changes. And as a person is walking around or I imagine a small jump or walking upstairs that pressure is going to fluctuate a lot. And we would need to develop an algorithm or some sort of way that the device knows that there’s activity going on, that these slight pressure variations are going to change. So that’s our next step of testing is that we want to know or we want our device to not like oh you took a step so it’s going to tighten down on your leg and then all of a sudden you’re in pain that’s not where we want to take it. But that next step requires a person to be able to test it with us. So hopefully that answered your question. You can type in chat if you have more of that that you’d like me to iterate on.
I will read the next question. Amanda you asked: we were working with the local prosthetic company. What feedback did they have for our team regarding the direction we are heading with this design?
So far the local prosthetic company has been really on board with where we’re going with this project. At the beginning of last semester, so January of this year, we were brainstorming ideas all over the place and really throwing out these different ideas on where we wanted to have it. One of our ideas was have an air bladder that goes around your leg. That we have a small little pump that would increase or decrease just the the air around your leg. We worked with them and they said that the prosthetic that they recommend to a lot of their patients is that boa system that Garrett was mentioning that has a little knob that you tighten down when you need to. And we took that idea and we really didn’t want to try and reinvent the wheel if you will. There’s something that works but we wanted to make it work better. So we, especially when we had to do basically our half of our project remotely we really didn’t want to be adding extra variables that could potentially cause damage or not work very well in the time frame and working conditions that we had. And so we did go with modifying their manual tightening system into making it automatic. And they’re really on board with it. And depending on how their reaction to necessarily the final we might be able to even work more with them and they could even take the project into with some real patients. They haven’t confirmed that though so I’m just putting it out there they have not confirmed that they’re letting us test on real patients yet.
Yeah you’re welcome.
Yeah one issue with kind of the technology behind it is, so we’ve done the whole project based on the prosthetic they provided with that we have been modifying throughout the course of the semester. And this one prosthetic is was custom fit to a person at one point and so to test it on a real person it would have to be the person they designed the socket for. And so with the pandemic and everything is going on we were unable to get human testing done for this project.
Did you guys run across…? There’s a few other companies here in the country that do similar things. I worked for one in the Bay area called Lim Innovations L-I-M. I don’t know if you investigated and found them out but yeah, I spent a lot of time working with them on above knee and below [inaudible] sockets. And they use the boa system and some other technology, but go out there and take a look and see what they’ve done just as another reference of kind of what out what else is being done out there. But Lim Innovations L-A-M.
Thank you. Thank you for that.
So Josh asks: you spoke about battery life what kind of battery life did you get and how would it respond if the battery died? Could the system go back to manual?
Aaron might be a little bit better suited to answer that but my my best guess is… so we we used a 12 volt battery source which was kind of a big block battery that wouldn’t be ideal at all for the final integration of the system. It’s very heavy and very bulky. So we weren’t able to test for maximum battery life given our current situation and that’s why I think we set going forward we need to find a battery that works for our prosthetic and also is you know fits the other criteria of being rechargeable and having long life. As far as how it would respond if the battery died I think Aaron would probably best
answer that one.
Right. Well yeah, the thing about the battery is that it’s kind of – once we get the design completely taken care of it’s simple to, relatively simple to just get a smaller more powerful battery pack to operate it. Kind of untethering it making more more mobile is you know kind of what some of our next steps. But as far as reverting to a manual, our current design does not allow for that. We had to completely remove the the manual system in order to get the motor to actually be working and operating correctly and that is one issue that we know of which is why kind of those safety, those safeguards that we want to eventually put in place like the kill switch for if something starts malfunctioning for some reason. Or even if you know once it gets to a certain level of battery so it doesn’t just die and it’s clamped onto your leg, being able to somehow send you a signal and you know maybe even automatically do it after enough warnings and such so that you’re not just stuck. Or even like a potential would be a secondary smaller battery so that if the main battery dies you can still operate enough to at least turn loosen it and get it off your leg. You know these are things we’ve considered but certainly did not have the opportunity to implement those steps into it.
One of the design choices we made in regards to that battery is if you just have a regular 12 volt battery you’d have to have current flowing through it the entire time to have it keep the same position. We realize that that would be a big flaw in our designs that would kill our battery really fast. So we opted to go with what’s called a worm geared motor it’s basically a motor that two gears that are situated in such a way that you cannot turn one side of the gear. You can only turn one side of the gear to activate the other. So this is important in our design because we don’t want our motor to be able to be back driven. So example if a person jumps and then all of a sudden there’s a spike of tension in our cable, we don’t want our motor just to spin out of control and then all of a sudden they’ve landed on the ground and they’ve lost control of their prosthetic. So we wanted we made sure that it’s a worm geared motor so that it would conserve a bit more battery life and want to be back drivable.
And that is our time we’ve got about three minutes until the next session starts. We’re more than willing to hang out and talk if you want to you know ask more questions or just talk about our project some more. But yeah, that is our time if you’re wanting to get to one of the next presentations as well.