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Background

Over past few weeks, the Open COVID19 Community has seen a large number of makers contributing to the safety and convenience of the frontline healthcare workers worldwide, by designing and fabricating face shields and masks. This is a classic case of tools of Personal Fabrication coming together to use global network of fab labs and skillsets to serve for local needs of their medical facilities. Of course, our 3D Solutions have played key role in this pursuit. We, at SIMULIA, picked up some of the popular faceshield and mask designs from the Innovation Funnel of this Community and ran several batches of PowerFLOW Simulations to better understand the real life performance of these faceshields and masks, especially in context of a human sneeze, which technically is a convulsive expulsion of air and water droplets from the lungs through the nose and mouth.

Objective

The objective of this Post is to share results of the Simulation exercise across four popular designs that are in circulation in different parts of the world. Please note that the simulation(s) by Dassault Systèmes and other technical or operational information represented in these video are presented as an illustration and are for informational purposes only. Any use of information presented in or derived from this video is at the viewer’s sole risk and Dassault Systèmes disclaims all related liability. Also, makers need to exercise their own engineering ingenuity in coming up with design solutions with the insights gathered through these videos.

Let's dive into each design separately and then we will end with a series of general observations as revealed by our simulations.  

Note: Images and videos here indicate the contaminated surfaces using a red/purple color scale. You can observe traces of droplets/ contamination on both, the surface of visor/ face shields, and the face of the user, when he/she takes it off.

Prusa Design 

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Version 2: Rc3 headband with Longer Visor

Version 3 Covered Rc3 headband with Standard Visor

Version 4: Covered Rc3 headband with Longer Visor

Observations from the simulations results:

• As can be seen in version 1, the headband cover can further protect the shielded person by reducing the number of sneeze droplets falling from above that can contaminate the face (indicated by the yellow arrow)
• As in version 3, the headband cover is seen to arrest some of the sneeze droplets (indicated in red arrow), this could be valuable information in case the face shield has to be disinfected for later use.
• Simulations indicate that a longer visor tends to protect the forehead of the user in a more effective way.

ME-2300 GOTG Design

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Observations from the simulation results

• The flap has protected the forehead from the sneeze droplets.
• As can be seen on the face, sneeze droplets have fallen from above and contaminated the face. It is advisable to have a slightly larger flap or add a cover at the headband.

Laser Cut Design

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Observations from the simulations results:

• The shielded person’s face tends to be protected by the headband cover because it can reduce the number of sneeze droplets falling from above.
• The holes at the headband cover have not been taken into account in this simulation due to a few factors including a small diameter size. It is advised that if possible these holes should be minimized in future iterations of the design.
• The headband cover is seen to arrest some of the sneeze droplets, this could be valuable information in case the face shield has to be disinfected for later use.

ME-2300 UV-Clean Design

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Observations from the simulation results:

• Simulation indicates that the headband cover tends to protect the shielded person by reducing the number of sneeze droplets falling from above that can contaminate the face
• The headband cover is seen to arrest some of the sneeze droplets, this could be valuable information in case the face shield has to be disinfected for later use.

General Feedback

These simulation studies below show the trajectory of particles near the shielded person’s mouth and nose area, as a general reference case. As observed in all the simulations we have run (with different face shield models here), small particles are drawn behind the shield, and the shielded person could inhale those particles.

Therefore, it is to be noted that a face shield/ visor offers an additional layer of protection along with the use of a mask. This is evident from the 2nd & 3rd video below and the accompanying images.

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