Designing a Custom 3D Printed Ankle Cage Implant
Designing a Custom 3D Printed Ankle Cage Implant
Designing a Custom 3D Printed Ankle Cage Implant
Collapsible Inhaler Spacer Design
Background and Motivation
Approximately 25 million Americans today have asthma. About 5 million are patients under the age of 18. Common symptoms in patients with asthma include shortness of breath, wheezing, coughing, and chest tightness. Many of these symptoms can be relieved through the use of an inhaler- a device that delivers the relevant medicine straight to the lungs through a quick puff of air. Although using an inhaler seems to be relatively straightforward, some patients (especially kids), can have a hard time coordinating the spraying and breathing motions. As a result, up to 60% of medicine dispensed through an inhaler won't make it to the lungs.
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Through the use of an inhaler spacer, the medicine has volume to diffuse through a designated space before reaching the mouth. This allows the patient to breathe in without having to coordinate their breath with the inhaler puff and get more of the medicine into their lungs. However, current inhaler spacers are bulky, hard to carry around daily, and can be an insecurity for patients, especially kids who face judgment from their peers. The goal of this project was to create a fun, compact, and destigmatizing spacer that still serves all of the intended functions.
Design Criteria
The spacer has to have a sufficient amount of volume to allow the medicine to diffuse through before reaching the user. The spacer must include a port that the inhaler can attach to, a mouthpiece for the user to breathe in through, and one-way airflow valves that let air into the spacer when the patient breathes in. Lastly, the spacer should be lightweight, easy to disassemble and clean, and easy to carry around and store.
Mood Board
Early Sketches
Some key words that were important to the initial design of the spacer were: Compact, Clean, Comfortable, and Playful
Final Sketch Designs
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Initially, I thought of making the spacer look more like a toy through the use of interesting geometries and fun designs. I eventually moved away from these designs as the complex contours that come with "toy-like" inhaler spacers would likely make the spacer harder to clean and could potentially impede the uptake of medicine.
Final Model
LBM & BOM:
The finished inhaler spacer consists of three main parts: The top cap, the collapsible middle body, and the bottom cap. The top cap screws onto the collapsible body and houses the rotating mouthpiece that the patient uses to breathe in the medicine. The mouthpiece is pinned in place with a rod and can rotate up to 90 degrees. The bottom cap incorporates two plastic check valves and a port for the inhaler. This cap also screws onto the middle body. The two caps will be injection molded using ABS. Appropriate design for manufacturing guidelines regarding draft, overhangs, and wall thickness have been implemented in the design. The middle body will be injection molded using liquid silicone rubber. Several sections of the wall are thinner than the rest of the body to allow for proper collapsing of the body.
FEA Analysis
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An FEA analysis was conducted to determine the stress hotspots and overall safety factor for one loading condition on the spacer. In this case, the middle collapsible portion of the spacer was placed in tension, as a child could see it as a toy and pull on it for fun. A force of 200N was applied to the end of the spacer as this is the upper bound of maximum pulling force for children under 10 (the demographic that is most likely to do something like this).
This yielded a safety factor of 1.2 with the most stress being concentrated at the middle of the spacer.
A video documenting the design process: