Home' Inclean : INCLEAN Spt-Oct 2015 Contents 56 INCLEAN September/October 2015
By Mark Sisson*
It turns out that when you change the scale
of certain materials, new and amazing
properties emerge. Microfbre cloths, for
example, have had a tremendous impact in
our world of cleaning, and for good reason.
When you change the scale of the threads in
a cloth, making them super small, a new set
of physical forces come in to play.
Van der Waals forces, the same forces that
allow geckos to stick to glass with millions of
microscopic hairs on their feet, create a very small attraction between
the threads and various contaminant particles. While these individual
forces of attraction are small, there are millions of threads, creating an
almost vacuum like effect on particles.
Nanotechnology is even smaller, measured in nanometers or 1
billionth of a metre.
Microfibre and other Nanos
What does microfbre have to do with nanotechnology, you might
ask. Well, it's all about how physical properties of materials change
dramatically at extremely small scales. Take water, for instance. In our
macro-world, water is simply wet. But zoom in to the molecular level,
and water is electrically imbalanced, allowing the molecule to stick to
all kinds of different particles and break them down. Combine this fact
and the natural solvent action of water molecules with the attraction of
microfbre, and you have an extremely versatile and environmentally-
friendly cleaning system utilising these special micro-properties.
The individual threads in a microfbre cloth are 1/100 the size of a
human hair. But if we turned on our superman vision and could see
them at a nanoscale, these fbres would be huge.
Many materials at the nano scale behave in surprising, and
sometimes very benefcial ways. One such material is titanium
dioxide. In its normal form, Ti02 is the most widely used white
pigment in the world. It is added to everything from paints to milk
and toothpaste. And it's a valuable additive in sunscreen because of
its ability to block UV rays. But just like the threads in a microfbre
cloth, when Ti02 is manufactured as a nanoscale particle, some
amazing reactions are created.
Self-cleaning? You've got it
While the discovery that nanoscale Ti02 creates a photocatalytic
oxidation effect under UV light was frst documented in 1971, the
science has come a long way in 40 years. Today, specifc forms of
nano Ti02 produce a powerful photocatalytic oxidation reaction using
nothing but normal indoor light. The nano crystals that create this
reaction are around eight nanometers.
To put it into perspective, DNA is around two nanometers, a
typical bacteria 200 nanometers, and that microfbre cloth thread
is a whopping 1,000 nanometers. If we put on our cleaning hats
for a minute, it’s not too diffcult to imagine how useful a substance
could be that creates an oxidation reaction from light. Could this be
the 'holy grail' for cleaners? Could this create surfaces that oxidise
contaminants and kill pathogens automatically... dare I say 'self-
cleaning’ surfaces? It seems like science fction, but that’s exactly how
far this technology has come.
Because of the popularity of Ti02 and the advent of nanoscale
particles, there has been some speculation about toxicity to humans.
Most of the studies to date have been focused on the predominant
risk, which is the inhalation of a large amount of nano-Ti02 dust
in a manufacturing environment. With the correct application and
material science, self-cleaning surfaces involve Ti02 that is molecularly
bonded to the underlying material, preventing its release into the
environment and creating a long lasting self-cleaning effect.
The self-cleaning process actually happens in multiple ways. First,
the basic oxidation process happens directly with any organic
material that comes in contact with the surface, breaking down
the contaminant into base elements like water and carbon dioxide.
The second process, which will be of special interest to infection-
prevention professionals, involves the oxidation of water molecules,
which produce hydroxyl radicals.
While hydroxyl radicals have extremely short lifespans, existing
for less than one millionth of a second, they are extremely deadly to
microorganisms like bacteria, viruses, and fungi. And because the
process is oxidative rather than enzymatic or antibiotic, the surface
doesn't contribute to antimicrobial resistance or 'super bugs'. As a
side beneft, the oxidation process also continuously eliminates volatile
organic compounds (VOCs) and has even been shown to eliminate
greenhouse gases, such as methane and ozone.
What does this really mean to the cleaning industry and how can
this help us clean for wellness rather than just appearance? First, by
oxidising organic material, like bacteria and viruses, we can create a
surface that doesn't just look clean -- it truly is clean at a microscopic
scale. In too many cases, outbreaks from a specifc pathogen happen
in facilities that look perfectly clean. It's human nature to think a
surface is clean when we can’t see any dirt. But it’s all of those nasty
bugs we can't see that cause problems.
To put the issue into perspective, most hospitals look spotless, yet
100,000 people die each year from healthcare acquired infections
(HAI). Think of nanotechnology as billions of solar powered
nanobots, zapping those microscopic HAI-inducing monsters that are
invisible to the naked eye. And because these nanobots are catalysts,
nothing gets used up or gets released into the environment like some
traditional antimicrobials based on toxins or heavy metals.
Secondly, photocatalytic nanotechnology doesn't rely on the
diligence of people to be effective. Let's face it; humans are often
unreliable, or at least inconsistent, when given specifc tasks. Are your
cleaning personnel properly trained? Are they being monitored to
determine whether their work is effective? Do they always following
the dilution and application instructions for the various disinfectants
and cleaners that are being used?
Deploying technology as part of the cleaning process can help
overcome some of these issues and create a more consistent and
effective cleaning system.
Built to clean
So how can businesses beneft from the latest advancements in self-
the next big really small thing
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