Assistive Technology Project

Problem Statement

Over 2 million people in the United States live with limb loss (Zhu et al., 2022). This paper will refer to individuals with limb differences as ILDs. Amputation can be very traumatic for a patient, as it often limits their ability to perform activities of daily life (ADLs). Most qualifying amputees will choose to use a prosthetic device to offset the issues caused by the loss of a limb, allowing them some sense of normalcy with the ability to integrate into society without the need for constant assistance. The component of the prosthetic limb that directly contacts the residual limb to form a connection between the body and the prosthetic is the socket. When properly fitted, a comfortable socket can be extremely influential in maximizing the prosthetic’s utility in daily use, as otherwise the discomfort, or in some cases pain, will lead the amputee to abandon their prosthetic (Klute et al., 2001). Under the socket, ILDs must wear a silicone liner below the socket to improve comfort and safety (Zepeda, 2023). The silicone acts as a protective layer between the residual stump and the carbon fiber socket, providing equal pressure distribution and padding for the user’s comfort. On top of this liner, they wear many layers of socks to ensure that the prosthetic device fits snugly. Despite the benefits of using prosthetics and silicone layers, any amputees notice that after wearing their prosthesis for a few hours, especially if they were physically active in that period, their silicone liners can get very hot, and this often leads to discomfort in the form of irritation, infection, and an excessive buildup of perspiration, all of which may have a highly detrimental effect on quality of life (Ghoseiri & Safari, 2014). Many amputees with lowered quality of life will notice effects such as anxiety, depression, lower social output, and much more (Manz et al,. 2022), as well as a ceasing use of their prosthetics (Williams, 2020). In fact, over 53% of prosthetic users who discontinue use cite discomfort as a primary reason, suggesting that a cooling solution could mitigate non-use by overcoming these side-effects (Webster et al., 2023).

Design Approach

To build out our prototype, we started out by testing some initial design concepts. We had ideas for radiator-based cooling devices, Peltier-based cooling devices, and refrigerant-based cooling devices. We chose the Peltier-based option since it was non-toxic and it was cheap for its efficiency. We started by building out a quick prototype that follows our requirements, pictured in this section. It managed to cool water fairly effectively in our design studies (read more about them in our STEM II Final Design Study below). Because of this, we continued on with this design and worked on slight improvements that would bring us to our deliverable proof-of-concept prototype that examines how our device would work in the real world. For this, we bought new parts and designed a new device that was more compact and efficient.

Final Device

Our final design consists of an Arduino Nano that is connected to a motor controller, which then connects to a Peltier module and a motorized water pump. The Arduino is also connected to a 24V fan through a step-up converter. We use a 12V 2000mA power supply that connects to a wall outlet, and we use a breadboard to connect our power supply to our device. Connected to the water pump is a long stretch of tubing, with a thin 1mm OD tubing lining the inside of the prosthetic. A heat sink is connected to the Peltier module, and the fan is attached on top of the heat sink, adding with it a plastic shell around this part of the device. A resin-printed reservoir is attached between the tubing, serving as an easy way to load water into the system or to deposit water out of the system. In the future, we will mount our device onto a backpack or fanny pack so that it becomes wearable. We will attempt to increase the compactness of the wiring by putting the circuitry on a PCB (printed circuit board). We are hoping to include a probe temperature sensor to detect when the residual limb overheats so that the Arduino can automatically control the cooling as needed. To augment this, we plan to add Bluetooth connectivity to the device so that the user can use an app to choose whether the device should be activated or powered off.