Materials and Equipment:

Formlabs Form2 or Form3 SLA printer

Formlabs Flexible resin

Formlabs Durable resin

395 nm UV lights or a Formlabs cure station

Isopropanol bath or a Formlabs wash station with isopropanol

Filter material

• We recommend the mask base and clip components are used in combination with a filter material indicated for air filtration of .3 micron particulates that minimally impedes the exchange of air through the filter material.  
• **Members of Mercer’s faculty are currently testing filter material alternatives.  We will have data to report in the near future

Elastic straps (strap holes in STL file are ~.3in w x .1in h)

            McMasterCarr  item 8858T81, 3/32” diameter elastic cord

Silicone rubber tubing

• This is what we are using 1/8” ID, ¼” OD https://www.mcmaster.com/5236K506

**We found that scaling the mask and clip to 95% yields a mask that fits most peoples’ faces.  The 95% size passed an N95 fit test in the configuration pictured.  If you have larger diameter tubing or know the wearer(s) will have larger faces, a 100% scale version may work as well.

Our tested mask base component was printed on a Formlabs Form2 SLA printer using Flexible resin.  We used .5 density for print supports with 0.7 mm touchpoint size and mini rafts to attach to the print head.  All prints were washed in >95% isopropanol for 20 min in a Form2 wash station.  Prints were cured for at least 30 min with 395 nm or 405 nm lights at 40C. 

 And https://support.formlabs.com/s/article/Form-Cure-Time-and-Temperature-Settings?language=en_US)

• If you are printing a 95% size mask and a 95% size clip, it will require ~75 ml of resin.
• With SLA resins it’s important to fully cure your product. 

The mask clip was printed in Formlabs Durable resin.  We used .5 density for print supports with 0.45 mm touchpoint size and mini rafts to attach to the print head.  All prints were washed in >95% isopropanol for 20 min in a Form2 wash station.  Prints were cured for at least 60 min with 395 nm or 405 nm lights at 40C. 

The silicone rubber tubing was glued with Elmer’s Krazy glue just inside the face-edge of the mask. 

Filter material was cut into circles to match the mask opening.

Once the superglue was completely dry, the mask could be worn.   

The printed Flexible material can be cleaned with isopropanol, soap, and/or a bleach-based cleaning solution.  Repeated exposures to isopropanol is expected to cause the material to become less flexible.

We have tested prints in other materials and with other printing methods…

A print in TPU semi-flex filament on an FDM printer w/30% infill also yielded a satisfactory mask.  It also requires a silicone tubing gasket b/w the mask and the face.

The following people and groups contributed to the development, fabrication and testing of this mask:

Joanna Thomas, PhD, Mercer University School of Engineering

Sinjae Hyun, PhD, Mercer University School of Engineering

David Miller, PhD, Pittsburg State University

Jacob Sokolove, Mercer University School of Engineering

Sagar Patel, Mercer University School of Engineering

Brandon Matthews, Mercer University School of Engineering

Colin Petherbridge, Mercer University School of Engineering

Sarah Spalding, Mercer University School of Engineering

Gunhee Lee, Mercer University School of Engineering

Olivia Kight, Mercer University School of Engineering

Coliseum Medical Center, Macon , GA

Robbins Air Force Base SPARKS team

Jay Vizcarra, RAFB