Second skin
"We even have someone showing how this works by pouring red wine down
his silk tie into a wine glass!" says Ian George as he demonstrates
Dstl's liquid repellent coatings in a slightly more conventional manner.
Ian, a member of the Dstl technology transfer team has a piece of blotting
paper that is readily soaking up water. Meanwhile, in the other hand,
a seemingly identical piece of the same material is unable to do the
job it was designed for - the water droplets simply form beads and run
off the surface.
But this is no sleight-of-hand trick, apart from the moistness of the
wet blotting paper there are no physical differences apparent between
the two samples.
"It's always good to introduce people to the technology with a highly
visual but effective demonstration," says Ian. "It allows them to immediately
grasp the benefits of the process."
The display illustrates how an invisible barrier has been formed on
the surface of the paper, without any change to its physical properties.
But how is it done? Stephen Coulson, the man behind the technology explains:
"We use plasma polymerization techniques that can be applied to practically
any material - wood, metal, glass, textiles, plastics - to form a coating
that is incredibly liquid repellent," he says. "Even items constructed
from a number of different materials can be coated, which makes the
technique so unique."
The plasma coating works on the nano-scale, permeating the surface
of the material so that the coating actually covers the fibres, rather
than forming a barrier 'sheet' over the top. This means that the material
retains its original bulk properties - a textile will keep the same
drape qualities and will not stiffen or irritate while a sheet of metal
will retain its sheen and strength.
Plasma polymerization is a gaseous phase technique, conducted in specially
constructed plasma chambers under a vacuum. Plasma is a partially or
fully ionised gas or vapour and sits somewhere between a liquid and
a gas. In the case of the polymerization, different monomers are fed
in to the plasma process. The deposition parameters can be adjusted
to retain specific groups of the monomer, giving rise to a chemically
tailored surface. Conventional plasma processing would etch would strip
layers from a solid, but in the case of the Dstl plasma, a thin polymer
layer is added instead.
"There are a lot of companies using plasma chambers and several academics
are working on advanced plasma chemistry, but no commercial outfits
have yet combined the two," says Ian. "We have the expertise at Dstl
to do just that."
Origins and initial applications
The idea for the plasma polymerization has been several years in development.
Originally the result of a MOD-funded research project at Durham University,
the Intellectual Property now resides in Dstl Porton Down. Stephen has
worked on the project since the days in Durham and cites an operational
requirement for its conception. "The MOD wanted to find a way of creating
an impenetrable coat to its NBC suits, to stop agents such as mustard
and other liquid threats entering," he explains. "They wanted something
that not only adds an extra dimension of protection, but is also comfortable
to the wearer. The plasma technology is the only way to provide a durable
polymer coating to a fully constructed garment."
Conventional NBC suits are understandably bulky due to the materials
needed to keep chemical agents at bay. The plasma coating can create
equivalent protection and can be added to normal fabric, making it easier
for the soldiers to perform their duties.
"The coating could, in the future, be added to full suits, rather than
individual components," says Stephen. "At the moment, materials in general
use are treated in sheet form. The plasma vapour merely needs to make
contact with the material to coat it. This is a great step forward."
At present the plasma chambers are too small to accommodate a full
NBC suit, but already the team is trialing with a US company that specialises
in such facilities. "Only once the technology is scaled-up will we fully
realise its military and commercial potential," says Stephen.
Open market?
In keeping with government policy Dstl has been actively working to
transfer the technology to civil applications and plasma polymerization
already looks set to make an impact on the private sector. According
to both Ian and Stephen, the possibilities for technology transfer extend
through a number of markets as diverse as sportswear, electronics, designer
clothing and medical instruments.
Although it's currently not a case of 'you've got it, we'll coat it',
there seems to be a buzz about the new technology and its benefits to
the civil sector. Naturally, as with all MOD based IP, there are several
limitations, but the proof of concept stage is continuing apace.
"We already have several parties interested in licensing the patents,"
explains Ian. "And we hope to set this up as a spin-out venture as and
when it's appropriate."
Ian is the man responsible for the technology transfer and IP decisions
within the plasma team. He explains some of the potential market applications:
•Textiles/Clothing
This is perhaps the most obvious application of plasma polymerisation,
using the technology to coat fabrics and full garments. The plasma coating
is durable and extremely liquid repellent; it's surface energy is one-third
the value of PTFE or Teflon™ .Furthermore, it can be applied to
almost any fibre type - and because the coating is exceedlingly thin,
the breathability of the garment is unaffected.
Another key benefit is that complete garments can be coated, rendering
seams, zips and fasteners liquid repellent. Dstl is working with leading
sportswear companies and manufacturers of luxury fashion brands to develop
a new generation of water repellent and stain-resistant clothing.
Spilling a drink down that expensive silk tie may not draw as many
gasps from dinner guests in the future, but plasma coated garments will
still be able to be washed as normal. "It eases the cleaning process
because it is a barrier between the stain and the garment," says Stephen.
•Medical
There is a multitude of applications in the life sciences sector and
already the team has been coating medical components using the small
plasma chamber at Porton Down. "The coating is bio-compatible," says
Stephen. "This means it can be used in a range of medical and healthcare
applications. Because the coating reduces the attachment of bacteria
and the adhesion of material such as mucus and blood it is ideally suited
to coat things such as catheters, IV lines and critical care vents."
•Electronics
From mobile telephones, personal computers and cameras through to computer
chips and circuit boards the raft of applications in the electronics
sector looks vast. "The coating will add a layer of unbeatable water-repellence,"
says Stephen. "Even the nightmare scenario of spilling a sugary drink
on your computer will suddenly carry less weight!"
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