N95 Mask with Integrated Nasal Cannula

In the midst of the COVID-19 pandemic, individuals who require a nasal cannula full time are at a much higher risk of extreme illness from everyday pathogens, and cannot use the standard N95 masks that exist since the cannula tubing breaks the seal of the mask, rendering it useless.

Role

Mechanical Engineering Student

Team

5 Mechanical Engineering Students

Course

Capstone Design

Date

Nov. 2020

 

Scope

To design an N95 rated mask that interfaces with nasal cannulas to provide at-risk individuals the highest level of protection against viruses while accomodating their medical needs.

 
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INdividual
Contirbutions

  • Design brainstorming

  • Prior art research 

  • Design criteria development

  • Filter cage mechanism CAD

  • Main body CAD

  • Face seal CAD

  • Face seal material selection

  • Manufacturing research 

  • Silicone molding

  • Final mask build and testing

 

Design Brainstorming

Prior to performing any research, the team decided to brainstorm every potential solution that came to mind. This led to many kinds of designs, from feasible to complex to ridiculous. Shown below are some of the most noteworthy design ideas, as well as some that eventually contributed to the final design.

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Prior Art & Design Criteria

To begin defining design requirements, prior art and related technologies searches were performed to discover where the market fails to solve our problem statement and what technologies we could build off of. Our team also created questions for potential users of this product and distributed a Google Form to support groups of individuals in the target market.

 

This research provided guidelines to begin defining design criteria beyond the initial scope of the project, such as creating a reusable mask over a disposable one and including an exhale flap to improve the users' ability to exhale.

Prior art we looked to for inspiration included the Envo mask, the AirPro HEPA filter mask, and a study integrating an oxygen mask and N95 mask.

Many brainstormed ideas were eliminated at this phase due to the timeline of the project. The team was concerned with ideas that included embedding mechanisms in the N95 material, as the filter material and the cannula were to be replaced at different intervals. This meant either overly frequent replacement of the cannula, wasting the consumer's money, or too infrequent replacement of the N95 material, rendering the mask dangerous to the user after 8 hours of use.

Due to this, it was determined that the N95 material and cannula had to be independently integrated with the final mask assembly. We decided to repurpose a readily available N95 mask material, the Envo mask filter, and design the remainder of our subassemblies around that filter geometry.

 

Design

I was the primary designer on the main body, filter cage, and face seal, while I integrated the work of my teammates into the overall assembly.

 

Designing the main body required understanding the design constraints of all subassemblies and accomodating them in the design. Due to this, I designed the mask referencing key dimensions, such as the thickness of the material used as a mask gasket and the Envo filter material dimensions. This allowed for fast iteration when certain design changes were made.

The face seal design was based on those found in standard respirators. This geometry is intended to be flexible enough to conform to various shaped faces while still sealing properly. To design such curves, I took it on myself to learn surfacing in SolidWorks. 

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Manufacturing

The N95 mask build was an iterative process, with small-scale tests on subassembly functionality informing assembly implementation. Though these tests, feature dimensions and placement in the final assembly were determined. 

To avoid a potential pitfall of FDM 3D printing, layer gaps, the mask was 3D printed using an SLA printer. Layer gaps would render the filtering properties of the mask ineffective. Clear resin was used to allow for observation of interactions between parts in the product, providing feedback for future iterations.

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To create the face seal, I surfaced a negative of the SolidWorks model and split the negative to create a core and cavity for injection molding. Then, I 3D printed the mold and manually injected Smooth-On Dragon Skin Silicone Shore 30A to create the face seal.

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Finally, all components were attached to the mask body, using either silicone glue or posts and pins.

 

Demonstration

 

Capstone Panel Presentation

 

Final Report