Research into Upper-Limb Prosthetics

Limb loss has huge implications on a person’s quality of life, especially if it’s the loss of a hand or arm. In the United States, we are fortunate enough to have a wealth of options for hand and arm prosthetics. In other countries, this is not the case. Access to affordable, functional prosthetics is limited in many developing countries – and even if accessibility was improved for amputees living in these regions, the kinds of prosthetics that we offer in the US would not be practical. This is because:

  1. They cost too much to manufacture and purchase in regions where families live on small incomes.
  2. They are not designed to hold up in humid or sandy climates, and therefore the sockets can hurt the wearer’s skin.

For several years, students in the Undergraduate Summer Research Institution at Saint Ambrose have been working on research related to prosthetics design under engineering professor Dr. Jodi Prosise. A major component of this ongoing research has been to develop a cost-effective prosthetic limb that could be worn in humid climates and manufactured with local materials. The limb had to be durable, lightweight, and breathable.

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Previous groups of students have developed prototypes of a prosthetic arm using PVC, wood, and twine for a man in Brazil named Milton. Milton is a quadruple amputee who had to have both of his arms amputated above the elbow after an electrical accident. The most recent two prototypes have been sent to him to test. For this Session of USRI, we have been working on three main goals:

Our main goal has been to recreate the prosthetic limb mentioned above to use as a demonstrative model on campus. We have made the pieces of the arm and are currently assembling it. The arm has an elbow joint and comes with four end-effectors, or replacements for a hand. These include a toothbrush, a pen, a spoon, and a fork. There is also a change-out station that can be nailed to a table so that a wearer with no hands (like Milton) can change out his end-effectors independently. In total, it costs less than $50 to build. Once we have finished assembling the arm, we are going to write an instruction manual for it by combining information from two previous research reports. We plan to add a supplies list and clear step-by-step instructions. Then, we will investigate ways to construct an end effector that can do a basic grabbing motion. This could be mechanical or use a small electrical motor.

Our second goal has been to learn about EEG waves and brain-computer interfaces. EEG waves are electrical signals that can be picked up from the skin of a person’s head using electrodes. They can be displayed on a screen by an EEG machine, much like an EKG machine displays a heartbeat. There are several different kinds of EEG waves and they fluctuate based on our brain activity. A brain-computer interface, or BCI, is a piece of technology programed with software that picks up EEG waves and uses them as signals to interact with something else. The field of biomedical engineering is wrought with research studies where researchers are trying to use BCIs to decode EEG signals from our brain’s motor cortex and use those brain signals to move a mechanical hand. As for us, we learned how to use a BCI called OpenBCI to see our EEG waves on a computer screen. We attempted to develop a program that would allow us to blink and light up an LED, but we discontinued these efforts for the moment as it required a lot of programming knowledge, and none of us have a strong background in programming.

This brings us to our third goal: learning how to use a muscle sensor to move a 3-D printed hand. During our attempts to program the OpenBCI, we learned the basics of how to program a computer chip called an Arduino. We placed an order for a muscle sensor that runs on this software, and hope to write a program that will use electrical signals released from muscles when they contract (called EMG waves) to a control motor hooked up to a 3-D printed hand. The designs for the hand came from an open-source blueprint online. We would like to be able to use the EMG waves to make the 3-D printed hand open and close a grasp. This is similar to myoelectric prosthetic hands available in the US, that run on muscle sensors.

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