Mask Open'AER : a locally produced FFP2 replacement mask

An open source solution for fast and local reusable FFP2 mask manufacturing.

Introduction

Problem and Background

The Covid-19 pandemic is a global crisis. One of the biggest problems is the production of medical supplies and as Covid-19 is a respiratory disease FFP2 masks are especially important. Unlike surgical masks that stop the person wearing them to spread the virus, these masks can be used to be protected from the virus. They are therefore necessary for medical workers. There is a shortage of FFP2 masks and it put the life of medical workers at risk.

The quantity of masks that the French industry can produce is limited and it is very difficult to import them as all the countries want them. A DIY FFP2 mask could be a way to produce these masks in a decentralized way, in France and in all the countries that need these masks and will continue to need them, especially third world countries.To have a functional FFP2 masks it needs to be :

Completely hermetics
Flexible so it can be used on all faces
Can be produced locally and quickly
Autoclavable, reusable
Adapts to different types of filters (manufactured, DIY in urgent situation)
comfortable to wear

Solution summary in simple terms

We developed a process to produce high quality reusable ffp2 masks that can be produced easily and locally.

The masks are silicone casted in a 3d printed mold and filters are made from polypropylene sheet, an easily accessible material in hospitals and approved by DGA, the French Defence Procurement Agency.

Solution summary in technical terms

Masks are silicone casted in a 3D printed mold, the mold is printed in about 20 hours in an FDM printer using any filament (we used PLA). A mask is made with 75 ml of Silicone with a shore of 25 and skin safe (PlatSil® Gel-25 Silicone Rubber is an example of silicone that can be used for the mask). A mold can produce a mask per hour.

DGA, the French Defence Procurement Agency approved the use of SMS (spunbonded / meltblown / spunbonded) laminate, a sterilization wrapping sheet highly available in hospitals, as replacement for FFP2 filter. A circular piece of the SMS sheet is tight to the front of the mask using a snap-ring or a rubber band.

State of advancement of the project

We finished our first prototype. It has been tested and validated byProf. Philippe Juvin, Head of the Emergency Department of the Georges Pompidou European Hospital.

We are in the process of making 20 masks to be tested in several hospitals.

Project Timeline

12/04 : production of 20 masks to be tested (V2)
16/04 : production of 100 masks to be tested (V3)
21/04 : validation of the final version
26/04 : project is online (stl file and tutorials)

Project Implementation

A 3D printed mould to manufacture FFP2 silicone masks with a filter in SMS sheet (polypropylene).

These masks are intended for medical personnel.

Our solution is composed of 3 elements:

the 3D printed mould in which the silicone is poured
the molded silicone mask
the filter material (SMS polypropylene sheet)

A. Mold

The mold prints in 13 hours without support with a 3D FDM printer in PLA. it is in two parts, the base and the press.

B. Mask making process

C. Filter material

Our aim is to provide a reusable and hermetic frame for inserting filters. It must be adaptable to different formats in order to be able to use filters from industry or DIY.

The best solution identified is the material used to package surgical materials during sterilization. These are non-woven Spundbond polypropylene sheets. They have been validated by the DGA for use as a breathing filter.

link : https://www.ahlstrom-munksjo.com/products/medical-life-sciences-and-laboratory/sterilization-wraps/reliance-sms/

Methodology

The stl file of the mold is designed with Fusion 360. We print it using our 2 3D printer, a creality ender 3 and an ultimaker 2+. We use the Slicer Simplify 3D.

The filters that we will use for the test are … In the final product we will use by polypropylene sheet, specifically the product Reliance SMS 200 from Ashlstrom that has been validated as a filter suitable for FFP2 by the DGA (French Defence Procurement Agency).

To test the masks we use silicone RTV 3481 (shore 19-25). This silicone is not suited for extensive skin contact. The final product will be made in We will use the silicone PlatSil® Gel-25 Silicone Rubber that is suited for extensive skin contact.

The test of the efficiency of the mask will be done by medical professional from APHP.

Results/Expected results

We already have a first prototype of the masks. We will soon have the second prototype. We have already arranged for our prototype to be tested by physicians from the Georges Pompidou hospital.

Our final goal is the development of a process of quick production of reusable FFP2 masks. It will be made available online.

This will allow the production of FFP2 masks by the hospital that have their own 3D printers by companies or by groups of volunteers.

Safety, quality assurance and regulation

In order for the masks to be used safely, the silicone must be adapted to skin contact. it is the case of our selected silicone.

If the mask is not efficient, it can imply safety risks as the user will not be protected.

This is why we use a filter that have been validated by the DGA. The efficiency of the mask will also be validated by medical worker in order to avoid contamination it must be possible to sterilize the masks.

Our solution allow them to be sterilized by javel water or autoclave (prion cycle : 134°C, 18 min).