JET PRESS, a Nottinghamshire Engineered Fasteners supplier, is working with Rolls-Royce, Aston Martin, Multimatic, the Manufacturing Technology Centre (MTC) and the NHS on a revolutionary new Aerosol Generating Procedure (AGP) Shield. Fir Tree Buttons and Plastic Screw Cover Clips normally used in furniture manufacture play an important role in the finished product.
What is an Aerosol Generating (AGP) Shield?
Many front line healthcare workers in the NHS and around the world have caught the COVID 19 virus. The virus is airborne, so just being close to someone with the disease can be fatal. Of course, health workers have to be close during procedures like intubation and extubation (inserting and removing breathing tubes).
The AGP Shield provides a high level of protection to the medical team. Following trials in hospitals including St Bartholomew’s, The Royal London Hospital and the Royal Derby Hospital, medical teams are happy they can use them for patients on ventilators. They are also suitable for use in Intensive Care Units and Operating Theatres and in future Dentists may be able to use them.
Computerised Fluid Dynamics (CFD) testing of the shield showed the spread of airborne particles is reduced by almost 90%. The patients’ breath condenses on the inner surface of the shield, rather than into the room. This reduces the cleaning time in areas where procedures are undertaken.
Design and Development of the AGP shield
Rolls-Royce and MTC engineers worked closely with NHS teams to develop the first prototype. Alan Pardoe of Rolls-Royce said of the process “In Aerospace I’m used to projects taking a couple of years. We had the first prototype of this AGP Shield ready in a week.”
Danny McGee of MTC said they used WhatsApp to get feedback from medics using the prototypes. “We soon realised the clinicians work around the clock when we started getting messages from them at 4am”.
After the initial trials engineers from Aston Martin and their supplier Multimatic were brought in to refine the design. This next iteration was made from Polyethylene terephthalate glycol (PET G). This allows the shield to be vacuum formed. It meets the high optical requirements of the medical teams and it’s very strong. Silicone sheets over apertures allow the medics to get their hands and equipment inside the shield so they can care for the patient without significant exposure to the virus.
How to fix the silicone to the PETG?
This is how Alan Pardoe explained the challenge to Martin Critchley, Group Sales Director of JET PRESS. “The design started off by using metal nuts and bolts to hold the silicone sheets in position, however these make the shield heavy and difficult to clean so we have been hunting for solutions. We have tried bonding the silicone directly to the shield, and have also tried various plastic fasteners but unfortunately all of our current attempts have failed for various reasons. So I am contacting you to see if you think you may be able to help with a plastic fastener from your current range?
The fastener needs to be simple and quick to use, and needs to have a smooth finish on the inside to allow for easy cleaning. It must be able to cope with varying thicknesses of material as the shield itself is vacuum formed and therefore the material thickness varies from around 5mm to 2mm. It can be single use, but the main requirement is that once used it must provide a tight fit. Some of the plastic fasteners we have tried pull apart too easily and so when the medics have lifted the shield by the front silicone flaps the fasteners have “popped” apart, which is obviously not a good solution.”
Fir Tree Fasteners to the rescue
If you are not familiar with Fir Tree fasteners, look at the seat when you next go on a train or a plane. The small plastic studs holding the fabric on are the top of the Fir Tree Button. If you are familiar with these fasteners you might call them Fir tree Clips or even Christmas Tree clips.
You will find them almost everywhere, especially the furniture industry. JET PRESS have even supplied some to students designing a light aircraft to carry drugs to people trapped in war zones.
For the AGP shield Fir Tree Buttons are an easy to use, reliable, lightweight and cost effective solution. The problem was that the sharp end of the Fir Tree button was exposed on the inside of the shield. This could snag on gloves and make cleaning more difficult. So, JET PRESS paired the Fir Tree Button with a Screw Cover Clip to provide a smooth finish inside.
This use of furniture fasteners in a medical environment helped deliver an AGP shield that is strong, easy to clean and stacks neatly.
The final challenge the team faced was how to transport the shields back and forth to the hospitals for testing. Fortunately, Aston Martin needed to road test their latest DBX model so they used moving the shields as road tests.
Although this solution is working well, Danny and his team at MTC believe it can still be improved. They are working on a bespoke Fir Tree Button and clip that will make the manufacturing process simpler. JET PRESS will then look at the implications of manufacturing the new fastener designs. Once this stage is complete the AGP will be ready for mass manufacturing for use in the NHS. And potentially around the world.