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Prototype Development

PAPR hood for healthcare heroes

April 08, 2020

Days after receiving their first shipment of Badger Shields from Midwest Prototyping, the University of Wisconsin Hospital sent Lennon Rodgers of the UW-Madison Makerspace a list of their top 10 most critical needs to build up a supply of protective equipment ahead of the anticipated mid-April peak of COVID-19 cases in Dane County. Near the top of this list were Powered Air Purifying Respirators (PAPR) blowers and hoods.

Their goal is to outfit every health care worker with PAPRs – an amazing piece of equipment used to filter air and inflate a bubble around the wearer’s head to reject any contaminants. The Badger Shield team quickly realized that they could use much of the materials and knowledge gained in the face shield effort to design a low-cost, easy-to-manufacture hood to connect to the commercial blowers the hospital was ordering. My experience designing and patterning soft-goods products and wearable medical devices as part of Delve’s offering is why I was asked to pitch-in.

Ready, set, sew!!!

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Jesse models the benchmark PAPR hood.
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On a recent Wednesday, I received an existing PAPR hood to use as a benchmark along with the general goal of adding a hood to the simplified Badger Shield. At the same time, Delve engineers and our partners at Midwest Prototyping and UW Makerspace were figuring out how to make a universal valve for different PAPRs to interface with this hood. 

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A reverse-engineered pattern.
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After creating a digital pattern based on the benchmark, I sent it over to Karl Williamson at the UW Makerspace, who laser-cut the pattern out of Tyvek, a breathable fabric that’s resistant to bacterial penetration. Brian Ellison from Midwest Prototyping enlisted his mom to try to sew it together.

While Brian’s mom built Prototype v.01, she and Brian texted me some trouble they were having with the stiff Tyvek material and stitching around the tight seams near the lens. Knowing that piecing together four to five parts in addition to sewing around the shield was not efficient or easy to do, I started from scratch and draped a muslin Prototype v.02 to see if I could make a one-piece hood. Even if this pattern wasn’t going to be an open-source pattern for at-home sewers, simplifying was still better.

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Corin and Jesse ideate over videoconference.
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The team video conferenced that evening to discuss learnings from Prototypes v.01 and v.02, ideate, and make a plan for the next day’s efforts. We decided to try the benchmark pattern first in order to quickly see if reverse-engineering was enough to move forward with better material.

In the morning, I ran over to Delve’s Madison office and grabbed all of the medical-grade textiles we had on hand from previous Human Factors studies we have done. Then I compared their properties to the benchmark hood to learn what features were essential to the function and which could be simplified. The PAPR pushes air into the hood, over and around the head/face and out through the gaps around the elastic neck closure.

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Jesse "porch tests" prototypes.
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Once I was done, my Delve colleague Jesse Darley, director of mechanical engineering, came over and we perfected our Social-Distance-Porch-Prototyping critique, where I would wipe down the protos with alcohol wipes, place it on the bench on my porch, and go back behind my storm-door so Jesse could try it on and talk through changes while 6-plus feet apart. 

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A UW Hospital staff member tries on a PAPR prototype at the hospital's loading dock.
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He then drove the prototypes over to the UW Hospital loading dock where anesthesiologists, nurses and other healthcare workers the team is in contact with could try it on and give us feedback while keeping a safe distance. Jesse would document with photos and video and our team would discuss iterations that evening via FaceTime.

The next morning, I refined the pattern, which is what makes our process a little different than the general “maker community” or rough prototyping. Pattern design is its own skill and I have been learning more and more about the nuances of not only planning out the construction of a garment but documenting it in a way other people can construct it. Someone has to look at the pattern and a set of instructions for assembly and be able to understand where to cut, fold, pleat, or attach pieces together. Pattern design matches well with my “day job” at Delve, which requires my team to consider how an audience understands and processes information in order to create clear and compelling visual communications.

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The paper pattern needs to be cut out and then used to cut out the fabric pieces.
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Each day, we would learn something else until we had this set of design criteria:

  1. Must protect wearer from exposure to the virus. Prototype v.04 added a full mantle to cover the head and shoulders rather than just the over-the-ear hood we started with. Full coverage was preferred by both the anesthesiologists and nurses we spoke with, so decided to pursue that first.
  2. Must be comfortable and adjustable Prototype v.03 tested out an idea for using an elastic shock-cord and toggle to allow for customizable fit, which was liked by the testers. Getting the curves of the pattern to go over the ear and squeeze the face in the right way was ironed out by Prototype v.04.
  3. Must be impermeable but flexible enough to inflate Prototype v.04 explored the one-piece hood with pleating design, which allowed the cap to billow and air to flow over the head successfully. The manufacturing group will be sourcing materials that align with infection-control guidelines as well as this functionality.
  4. Must focus airflow Prototype v.05 puffed up too much above the head and Prototype v.06 was too tight, making the valve point straight back which meant the hose running from the waist-worn blower would tug on the hood, so Prototype v.07 found the right balance of volume. I added a dart so the valve pointed back and down. We also cut the foam brow-band into three pieces spaced apart so air would flow over the face keeping the wearer cool and protected, and the lens free of condensation from exhalation.
  5. Must connect to any PAPR system Jesse Darley and Randy Koplin, another Delve mechanical engineer, designed a universal valve to fit three types of PAPR systems. Then Karl and Brian 3D-printed these parts quickly at the UW Makerspace so we were able to try out the prototypes by using a hairdryer.
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Team Badger Shield testing the last prototype with the actual PAPR device (not a just a hair dryer) at the UW Makerspace before we shipped it to our manufacturing partner.
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