Kind: captions
Language: en
in this U.S government lab they study
airflow to solve crimes
using mirrors lights and lasers they can
illuminate the tiniest differences in
air temperature and density and track
how drug powder settles in the rooms of
a house determine which person fired a
gun or spot particles escaping from a
sealed package
a portion of this video was sponsored by
caseta by Lutron
our best tool for picking up tree
substances has been the same for
centuries
so it turns out Nature has already
provided us with the best chemical
detector and that is the dog's nose
so this is Bubbles
she's a 3D printed anatomically correct
model of a female Labrador Retriever we
tried to get one of the police canines
to come in here and get in front of the
mirror but dogs get hungry and cranky
very quickly and we got about four
seconds of good footage and I'm like
okay we can do better than this and dogs
can sniff very faint since and from far
away but they don't do it just by
breathing in what they do is breathe out
and in rapidly around five times a
second
what I want you to notice is this
pulsating motion by the
um by the we'll call it the doggie treat
right this is our doggie treat if you
notice this pulsating motion and what
allows them to detect scents from far
away is the rapid and turbulent exhale
when the dog exhales there's a turbulent
air jet that comes out of each nostril
just like when you and I exhale if you
put your hand under here and just exhale
out of your nose those are two turbulent
air Jets coming out of the dog's nose
but when the dog is down on the ground
those air jets are vectored back towards
its rear the dog is pushing air back and
when by doing that it's pulling air from
ahead of it so imagine me
um blowing air this way and when I do
that I actually reach out and pull air
towards me the dog reverses flow inhales
right gets a new sample analyzes it with
an amazing chemical detector upstairs
right it's a factory region and does it
at five times a second
the on average a dog when it's sniffing
for something five times a second
repetitive sine wave so that's what
makes the dog this incredible sampling
system it kind of didn't matter the
breed of dog so somehow their their
evolution allowed them to figure out
okay one over five seconds is what I
need before I take the next puff or the
next inhale if the dog had a infinite
lung capacity and it just inhaled
constantly it has a very limited reach
but because of this in and out Bellows
effect its reach goes up by roughly a
factor of 18. as we actually we have a
number of commercially available Vapor
detectors okay some of these are really
good for various explosives and drugs
some are very good for a chemical and
biological hazards but they all just
inhale air what we did is we designed
and printed what are essentially
nostrils that plug onto this thing and
make it sniff like a dog and then by
doing a set of controlled experiments by
moving your Vapor Source farther and
farther we were able to on average
improve the detection capabilities of
these by roughly a factor of 16 to 18.
well just by making them sniff like a
real dog
we're able to see this dog breath using
schlieren Imaging I've actually done a
video on this before this is an
automotive headlamp after that I have a
condenser lens so it takes this light
and focuses it down to a point so from
there our light diverges and it comes up
and it fills our mirror think of these
this these light beams as arrows okay
and there are a bunch of arrows that are
coming up they're straight as can be but
when they pass something of a different
refractive index which could be the heat
from my hand or a different density
which could be a gas of a different
density
those light rays they shift a little bit
it should vary slightly okay they
refract they Bend then they all come
back
so we're coming back here and right here
we have a two-way mirror so light can
travel through the mirror this way but
when it comes back it turns 90 degrees
and if you look right here I have a
razor blade
and what this is doing it is positioned
exactly at the focal point of that
mirror I have that razor blade Edge it's
able to move in and out of the focal
plane and so what I do is I cut off
those arrows of light those beams of
light that shifted a little bit
and I cut them off I block them as I
move the knife edge out so I'm not
cutting off any light right now so you
basically have a really expensive mirror
it's not doing anything for you but as I
take this razor blade and push it in
you start to see you know turbulence in
the air and as I take it more and yeah
there you go get your hand in there
wow
your slurring setup is so much better
than mine
so take a look at this so this is in a
shadow graph system
so it's it's schlieren's little brother
okay it's not a slurred system but it's
very close it's Shadow graph Shadow
graph is not as sensitive
okay but it's easier to build
look we have a flashlight and a white
wall and we're already seeing a shadow
graph there so why does this work
what's happening is we have light it's
not as focused as I would like but the
more Focus the better
um the light's coming up this way it's
passing through a hot flame of a
different density and refractive index
and we're basically casting a shadow of
that plume on the wall which is why it's
called a shadow graph
these can still be used to visualize
flow patterns in detail just by looking
at the footage of guns fired in a shadow
graph we can actually figure out the
speed of the bullet and how loud the
bang was
and there's our bullet whizzing off uh
it is supersonic because it has a very
small bow shock you see it there very
very small so it's you know roughly what
mach 1.05 maybe just above Sonic compare
that to the infamous
AK-47 assault rifle there's there's two
things that we can qualitate
qualitatively observe here one is if you
compare these side to side the Smith and
Wesson versus the AK-47 the the the
darkness of this line is different this
is a quieter firearm it's not as loud
because it's not as loud it's less
pronounced it's less pronounced yep the
hot gases released when the gun is fired
expand outwards creating a shock wave
across this shock the pressure
temperature and density of the air
changes rapidly and the bigger that
change the darker this shows up in the
shadow graph so you can get a sense of
how loud it is by how dark that shock
appears and then here we see our our
bullet whizzing off at about
you could actually you could actually
measure that and calculate the Mach
number any object moving through air
creates pressure waves that travel out
at the speed of sound since this bullet
is moving faster than the speed of sound
the pressure waves it creates all get
compressed together into a single
conical shock wave it's like a tiny
sonic boom and you can use this to
determine the speed of the bullet the
sine of the angle is the ratio of the
speed of sound to the speed of the
object
there is a different way to visualize
flow which is with a laser sheet it
illuminates fine particles so we can see
the plumes of gunpowder residue created
when the gun is fired we call this laser
light sheet and the reason is okay so
now our lights there I can barely see it
because I have laser safety glasses yep
I can only see it in the camera yeah so
so what's happening here is we have a
laser beam and we send it we steer it
through a cylindrical glass rod
all it is is a piece of glass that's a
cylinder and what that does is it
spreads that beam into a two-dimensional
wall of laser light okay and so the way
this works is whenever particles or
theatrical fog cross through this sheet
they light up because of the laser
there's a lot of effort now going into
understanding gunshot residue so gunshot
residue is the kind of burned and
unburned propellant
that occurs whenever a firearm is
discharged right so what we're looking
at here is using laser lights and
high-speed cameras is we're looking at
the plume of gunshot residue that's
generated after a firing event
looking this is looking at ventilation
inside an actual gun range but look at
all this this is all gunshot residue
that you can't see with the naked eye
but it's there so you can imagine if
you're inside a home this is five shots
in a few seconds enormous amounts of
material a lot of this is landing on the
hands of the shooter
but unfortunately a lot of it is also
being dispersed into the local
environment it goes way farther than I
expected
so the question is can we differentiate
between
something that's actually been done by
the shooter and something say by a
bystander that walked in two minutes
later so that this is what we're
actively trying to pursue right now
so these are tools and techniques that
we use here at nist that are qualitative
or sometimes semi-quantitative but they
really help illustrate what's happening
and then the public security part of
this
deals with Trace Contraband detection
we're all generating heat right so we
all have this warm plume of air you want
to see it I'll show you
crazy
so you've seen it there
so that is called the human thermal
plume and guess what's in that plume
um water parts of me
skin cells
no way yeah so we're shedding skin cells
at a pretty creepy rate I forget what
the number is but it's a lot thousands
an hour ish so we're shedding these skin
cells constantly and uh it's actually
not necessarily A Bad Thing from a trace
detection standpoint what do you mean
well whenever we are talking about Trace
detection whether it's drugs or
explosives it's all based on this
fundamental principle it's called Low
cards exchange principle it's in
forensic science it's at every contact
leaves a Trace
and what that means is when you're done
in this lab there will be parts of you
left behind in this lab whether you like
it or not right because we're all
shedding skin cells and taking things
it's taking stuff with us so if I'm a
bomb maker if I'm involved in
manufacturing you know illegal fentanyl
in my basement I am ultimately
contaminating myself
with the bulk material and this
contamination comes in the form of a
very very small particles and the
chemical detection systems that we have
available now are so sensitive
they can detect
a single particle of say an explosive
explosive residue
imagine you have a uh a bomb in a
package
right and you're at some kind of
screening facility right you're at a
facility that maybe is screening things
coming in from overseas maybe you've got
a sniffer you've got a commercially
available Vapor detector and you've got
10 seconds to sample this package where
do you point your device
right these are the kinds of experiments
that help us understand where you should
Point your device
we call this burping we're burping the
package so we have some acetone in here
so wherever you burp it where you
squeeze it you have acetone Vapor coming
out of all the gaps right so they're
coming out in the Gap so that that Gap
gives you the highest chance of actually
detecting what's inside right you don't
want to go over here where there's no
gaps you don't want to go up there where
there's no Gap you want to go in these
Corners here where stuff is actually
kind of permeating through and outside
of the box
this is some recent work we're doing we
are basically simulating illicit drug
Manufacturing so here's some talc powder
right no big deal I'm gonna I'm gonna
shake it up a little bit when I open
this and squeeze
I can't see anything but are you seeing
anything in the camera yes
so again to the naked eye we'd never be
able to see this but because the laser
is doing The Illuminating for us we're
able to see this
[Music]
let's do a little experiment where I am
taking a legal substance a and pouring
it to into substance B first thing I'll
do
just watch when I take the lid off of
this
take it from here
there's a little bit coming off yeah oh
yeah it's still going
so just imagine
you're in a basement and you're building
stuff like this and you don't realize
that there's all this contamination
spreading and landing on other other
surfaces in your room
and I can't talk about the numbers but
they're pretty startling like there's a
lot it spreads everywhere there's a lot
yeah
[Music]
yeah full of smoke in here you ready yep
what I really love about the laser sheet
technique is it allows you to visualize
the turbulence that's in the air so this
is a way we can see how the airflow in
the room is actually being tracked
oh that's nice yep
[Music]
if you look at the graph in the top
right that is actually real-time counts
of the particles that are being
generated around this person so this
that plot represents
um basically inhalation exposure of the
materials that he's working with that's
crazy if you think about because that's
if that's Fentanyl
and that person doesn't have a mask on
they're gone we add fluorescent powder
to this kind of stuff so we can uh we
can actually visualize where the
contamination goes the other cool part
of this is that we can use a
quantitative method of sampling surfaces
in the house we basically use swabbing
it's the same idea when you go to the
airport you ever gone there and they ask
for your hands yeah right and they take
a little swab and they wipe your hands
what they're doing is they're looking
for these Trace Amounts of explosive
particles that could be on you if you
were involved in the manufacture of an
explosive device but that's a drone
that's looking at a drone and the
question is because you know you get
this cool prop wash and these four
propellers that are all interacting with
each other so the question is can we use
the fluid dynamics of a drone to do the
sampling for us and here's what I mean
by that if there is a suspected you know
manufacturing facility of something say
it's a methamphetamine or fentanyl you
know it's very very expensive to get
Hazmat Crews involved have them come
they have to gown up they have to go in
to a potential really dangerous
situation what if
we had a drone we just flew the Drone in
right it buzzes around and it's got some
special kind of collector on the belly
of the Drone and we're using the prop
wash of the Drone to stir up particles
off of the surface and then somehow
inhale them collect them the Drone comes
back to base you run your chemical
analysis you say okay the house is clean
or no we found stuff okay now it's time
to pull out the Hazmat crew you know so
the big picture idea that I want you to
keep in the back your head the whole
time is this idea of Public Safety and
Security
so that's really what happens in this
lab but underneath that kind of umbrella
term
think mask research so when the coveted
pandemic hit we kind of Switched gears
in here to try to address some of the
issues related to masks
this thing will actually breathe as a
human does that human happens to be me
so I measured my own kind of breathing
rate and then built a system kind of
engineered a pneumatic system that
replicates that but it also has a fog
machine a fog generator so this thing
basically just looks like it took a drag
off of a cigarette and exhaled what's
kind of cool with this is it looks like
there's nothing coming through right but
there's millions and millions of
particles being trying to make it
through some do because it's not a
hundred percent so I wrote an image
processing code so you take this
information you plug it into a code and
it analyzes based on pixels and it's
counting white pixels and sure enough if
you use an n95 you put an n95 on here
you run it through an image processing
code
uh guess what percentage of pixels light
up white five percent five percent
okay I just want you to breathe
naturally
so when you're inhaling it gets dark and
when you're exhaling it gets lighter
because the air is being warmed by your
lungs and then coming back out
like it's it's interesting how fast you
can see the effect of of the breathing
in like
like just makes it go dark so quickly
but that that shows me that like this
stuff doesn't change color at all so
this is being used to seal versus filter
it's I I noticed that color change is a
lot more dramatic yeah with this you
know it was it was in and out I feel
like it's a that's a thinner mask right
yeah so the heat transfer through it is
going to be greater
I feel like there's a lot coming out
over there yeah there's a lot if you
just breathe naturally you'll see a lot
coming out there
foreign
[Music]
masks right is like initially they were
like masks don't work don't wear a mask
and then they were like Mass do work
like and wear a cloth mask and then they
were like no no cloth masks don't work
like I don't know there was a lot of
confusion around masks what we learned
early on was that the communication
of you know you know mask Effectiveness
could have been improved right and so
that's kind of why I did what we did
with the schlieren the truth is the
average American is not going to sit
down and read a scientific journal
article but they will sit down and watch
a 90-second video of me coughing with a
mask on and off and that's that's what
we did
[Music]
kind of a unique relationship we have
with other federal agencies here so you
have a three-letter agency that has a
specific need for something right in the
security
um Arena what they'll often do is
they'll come here to nist and they'll
say hey we're really interested in
sampling people's shoes for explosives
for whatever reason right so what we do
here and in this lab in particular is we
figure out what are some good ways to
sample shoes for explosives
what are some not so good ways right uh
what do the measurements need to look
like
to evaluate a shoe sampling system
doesn't even exist yet and then what do
the standards need to look like that
support those measurements right and so
we figure all this stuff out in the lab
package it up nice and neat give it back
to the sponsoring agency and then they
take it to Industry an industry already
has a leg up on the development of these
kinds of systems because we did a lot of
the heavy lifting here in the lab
because with the success of uh you know
doing the covid related visualization
we're realizing now that the application
space for this kind of technology is
huge indoor air quality you can imagine
a bigger mirror where we could look at
two people interacting with each other
and what that transfer looks like from
one person to the other the take-home
message is flow visualization is a
critical tool that we use here at nist
to really help understand what's
happening right it's one thing to do
quantitative analysis on various
surfaces but now we can see we can
actually see what's happening and where
these particles are generated
foreign
thanks to Lutron for sponsoring this
portion of this video
perfect lighting isn't just important
for visualizing airflow it's also
essential for making your house feel
welcoming cozy and safe and with the
sponsor of this video caseta by Lutron
you can easily set up your own perfect
lighting you know caseta provides
premium smart lighting control including
switches remotes and plug-in smart
dimmers which allow you to customize
your home lighting from anywhere in the
house what I love about smart switches
is that one switch can control many
regular bulbs so you can effectively
make all your bulbs smart just by
replacing the switch and installation is
easy first make sure you turn off power
to the switch and then disconnect the
existing wires and connect them to
caseta's Smart Switch if you need any
help they're just a click or a call away
and then with the Smart Hub you can turn
your lights on and off just using your
phone or you can use another device like
Alexa or Google Assistant caseta works
with more smart home Brands than any
other smart lighting control system plus
their switches don't rely on Wi-Fi so
they always stay connected and you
always have control over your lights I
personally like setting timers in my
house for example the lights in my
office turn on by themselves in the
evening and this gives me peace of mind
that my family will always come home to
a well-lit house and the best part of it
all is if I'm already in bed I can just
check which lights are still on and turn
them off without having to run around
the house learn more about caseta at
casetawireless.com veritasium thanks to
Lutron for sponsoring that part of my
video