This course, taught by Dr. Crowthers. In STEM II, we form our own teams to create new products, focusing on assistive technology. Throughout the course, we research existing patents, collaborate with clients, and develop prototypes. Assignments include research papers, essays, reports, and presentations.
Cerebral palsy (CP) is a group of disorders that affect movement and muscle tone due to damage or abnormal development in the brain's motor areas. Moderate to severe arm impairment from Cerebral palsy can make brushing one’s teeth challenging, and in some cases, impossible without external assistance. Many people with arm impairments require a personal care assistant (PCA) to help them with their everyday needs. This poses a significant threat to a person’s quality of life, jeopardizing both physical health and independence.
To determine our first design, we reached out to people from Easterseals. Easterseals is a national Affiliate network that provides essential services to children and adults with disabilities, older adults, veterans, and their families. After reaching a client, we interviewed them over Zoom to get a general understanding of their needs. From there, the idea of a hands-free toothbrush was born.
First, we created various prototypes and tested them to see which prototype had the most efficient track run and would cover all sides of the teeth. We then used Onshape as our CAD software to model our prototypes. I did all the CAD work in my group. In Onshape, we used 3D-rendered teeth to give us somewhat accurate measurements for our final prototype. After many iterations and 3D prints, we ultimately landed with our final design. For our final design, we modeled and 3D printed a retainer-based toothbrush that uses moving brush heads to simulate traditional toothbrushing.
We kept the retainer case of the initial prototype, and from there, we removed the belts, which previously caused too much friction. Due to the high friction, the belt was replaced with a design where a belt is no longer needed. Our current design works by having a gear reduction. The gear is a 10-tooth gear and is placed on the stepper motor, which spins the gear to move the brush around the teeth of the user. The 10-tooth gear transmits its torque to a 3D printed 16-tooth gear, which meshes with a 12-tooth gear. The 12-tooth gear, in turn, transmits its angular velocity to a partially cut 62-tooth gear. The partially cut 62-tooth gear is 3D printed using TPU. Due to the firmness of PLA, when the TPU gear comes in contact with the PLA casing, the malleable gear bends in order to travel inside the retainer case. We also used a gear reduction to create an 8.266 times higher torque output to the TPU gear. This ensures that the TPU gear would spin as the torque that is applied creates a force stronger than the frictional resistance it rests on. Afterwards, a 3-sided toothbrush was attached to the smooth portion of the flexible TPU gear to ensure all 3 faces of the teeth are properly cleaned. A small circular spacer was added to the side of the retainer case to ensure that the TPU would run smoothly to the outside of the retainer case. A smaller PLA piece was added to the top of the retainer case in order to ensure structural integrity. The PLA gear and the spacer are spinning on a dead axle. The motor is attached to a DRV8825 motor driver.
The motor driver we use is connected to an 11.1V battery to power the motor; it also receives signals from an Arduino board to determine its direction and speed. The Arduino determines when to run the motor using buttons.
Below is the CAD of our currenty prototype. It has been scaled up and can be scrolled (sideways) so the gears can be seen clearly!