Thanks to Emerson for supporting this episode
of SciShow.
To learn more, visit Emerson.com/WeLoveSTEM.
[♪ INTRO]
Thanks to modern medicines and vaccines,
some of the worst diseases in history have
become preventable.
Like, smallpox is totally eradicated.
And we’re within jabbing distance of eliminating
polio, too.
Getting here hasn’t been easy, though.
These accomplishments are thanks to tremendous,
global efforts
to get medicine to essentially the entire
human population,
from American suburbs to the most remote inhabited
regions.
But getting medicine to everyone on the planet
comes with some interesting challenges,
because these drugs can be… finicky.
Some of them are pretty stable, no matter
the conditions.
But others are highly sensitive to light,
humidity, and especially heat.
Like, some medicines should be kept between
two and eight degrees Celsius…
which isn’t a lot of wiggle room.
In rich, developed nations, meeting these
requirements is often doable
thanks to elaborate, carefully-controlled
supply chains —
systems that get medicine from the lab to
the patient while maintaining its quality.
But for less developed areas — especially
those without easy, reliable access
to an electrical grid — this can be a serious
problem.
Coolers and ice packs can be a good last step
if you need to fly, drive, or hike
a vaccine or medicine to a remote community.
But to really address the problem, we need
solutions that can last a long time
and that can be more precisely controlled.
We need systems that can actually sense when
conditions are getting
too hot or too cold and can readjust.
And luckily, engineers have come up with some
options.
One alternative that’s been used for a long
time is kerosene or gas-powered fridges.
And before you ask, these aren’t just fridges
hooked up to gas-powered generators.
They work thanks to clever engineering and
physics.
First, you take a liquid refrigerant, like
ammonia,
and put it in a sealed container at low pressure.
The low pressure makes the liquid ammonia
start to evaporate and turn into a gas.
This change in its physical state absorbs
heat from the surrounding environment —
kind of like how evaporating sweat cools your
skin.
This sucks heat away from the inside of the
fridge, chilling it down.
Then, the ammonia gas is piped into a different
container filled with water,
where it mixes and forms a solution.
That solution is boiled with the help of burning
gas or kerosene,
then the resulting vapors are passed through
a series of separators and condensers.
Ultimately, you end up separating the ammonia
and water,
so the ammonia can flow back into its original
chamber
and start the cooling process all over again.
Different models might be set up slightly
differently or use different chemicals,
but that’s essentially it.
And this cycle can be repeated for about as
long as you have gas to burn.
Temperature, meanwhile, can be controlled
manually or with a thermostat.
And a thermometer and recorder can warn doctors
if the machine ever accidentally got too hot
or cold .
Kerosene fridges were actually some of the
earliest models of refrigerators,
and the old-school stuff sometimes works pretty
well.
This has been a common way to keep medicine
cold in remote areas
for the last 35 years or so, and these fridges
are used in
more than 60% of vaccine storage locations.
Of course, they aren’t exactly simple.
These things need consistent shipments of
fuel, and they’re not super-efficient,
so they’re now starting to be phased out
in favor of better and simpler options.
Like, for example, solar-powered fridges.
These are refrigerators powered by solar panels,
and like kerosene fridges,
they can come with thermostats and temperature
readers.
These devices first really came onto the scene
in the 1980s.
But unfortunately, while they did fix the
problem of having to keep buying fuel,
they also needed big battery systems to run
at night,
which could break or be expensive to repair
and replace.
So since about 2010, the preferred technology
is what are called solar direct-drives.
They still use solar panels, but instead of
using that energy to charge batteries,
they use it to directly freeze something like
water.
That keeps the medicine cool, and the ice
will last for up to a few days
even when the sun goes away.
They can also use something called phase-change
material,
which freezes like water, but at a bit higher
temperature —
like 5 degrees Celsius, rather than 0.
This still keeps things cool, but is less
prone to accidentally getting too cold.
Regardless, these materials don’t keep refrigerators
cool for as long as
an array of batteries might, so these things
might not be as good
for places with regular, heavy cloud cover.
But when you’re in an area with lots of
sun,
a short charge is good enough to keep everything
frozen.
These devices haven’t been extensively tested
in the field yet,
so it’s hard to make sweeping statements
about their lifespan.
But we have gotten promising results about
their reliability and ease of use
out of field tests in Tanzania, Colombia,
and Kenya.
While these things are more expensive to buy
up front,
they seem to be simpler and cheaper in the
long run.
And with more being developed all the time,
the medical community will probably see a
lot more of them.
Of course, solar direct-drives and kerosene
or gas fridges
aren’t our only options for transporting
medicines.
New research and design are happening all
the time,
and that’s pushing us into some interesting
territory.
For example, one project invented what’s
essentially a keg-sized,
heavy-duty super-thermos that could be carried
during a hike or a field trip
and that could stay cold for more than a month.
Vaccines in the center of the device are surrounded
by ice blocks,
and the entire inside compartment is then
surrounded by insulation
and a vacuum chamber, which keeps heat from
the outside getting in.
Small, onboard temperature sensors and electronics
can also sound an alarm
if the system gets too cold, which might alert
doctors to open it up
and re-pack things or move the vaccines somewhere
else.
This container was added to the World Health
Organization’s list
of prequalified products in 2015.
If a country or NGO is looking to buy or donate medical equipment,
this list tells them what the WHO thinks is up to the job.
It is not, however, the only option in development.
Student and design competitions have also
come up with coolers
that could be run off things like hand-cranks
—
basically, by using mechanical energy to power
a generator.
And other designs miniaturize existing technology
to portable sizes.
So whether it’s tried and true, new and
improved, or the cutting-edge,
we’re working on solving this transportation
problem.
Medically, we’ve already proven that we
have what it takes
to treat or even wipe out some diseases.
Now, we just have to keep our cool to put
the rest of them on ice.
Thanks for watching this episode of SciShow,
and special thanks to Emerson
for helping us make it!
If you want to learn more about who Emerson
is and what they’re about,
you can go to Emerson.com/WeLoveSTEM.
[♪ OUTRO]
