Week 3 Blog

In last week’s blog, I discussed studying the metacarpal region’s anatomy and testing a hand model’s ability to form a fist, revealing challenges in achieving smooth finger flexion. At the beginning of this week, I refined the model, and successfully improved its functionality. Below is a video demonstrating the flexion and extension of all four fingers.

https://www.youtube.com/watch?v=7u-oXqkElE8

Since this is week 3, I do believe that I should start my study of Electromyography (EMG) sensors early and explain how they will be used in my senior project. EMG sensors have a long history of use in prosthetics. However, before understanding how EMG sensors function, it’s important to grasp the physiology of muscle contractions.

When you decide to move a muscle, your brain sends a message to that muscle through nerves. This message triggers a surge of electricity along these nerve fibers. When this electrical surge reaches the muscle, it creates a chain reaction inside the muscle cells. Among these reactions, calcium ions rush into the muscle cells. These calcium ions act like keys that unlock the muscle’s ability to contract. Now, inside the muscle cells, there are tiny motors that work by pulling on protein filaments. When these motors pull on the protein filaments, the muscle contracts. The strength of this muscle contraction depends on how many of these tiny motors are activated and how quickly they’re pulling on the protein filaments. When you need to exert more force, your nervous system recruits more of these motor units, and they start pulling faster. This increased activity generates a stronger electrical signal, which EMG sensors can detect.
Once the EMG sensor detects the electrical activity it sends a signal to a circuit board. This signal then is translated into a command. The command generated by the EMG sensors will control servo motors, which in turn will manipulate strings connected to each finger ligament. If the string is pulled by the motor the finger will curl and once the motor rewinds the string will be pulled back and the elastic will cause the finger to uncurl.

Next week, I will have to research further how the signals from the EMG sensors are converted into a command for a motor. This will require some circuit knowledge and coding expertise.