High Speed Videography The Time Microscope

when i was an undergraduate

i was fascinated by how within a single

drop of pond water

i could see numerous alien looking

organisms with diverse ways of swimming

around

and capturing prey in the same way that

the microscope allowed us to rediscover

biology

at a different size scale i believe that

the high speed video camera

allows us to rediscover biology at a

different time scale

in a way the high-speed video camera is

a sort of microscope

into time the best part about this is

that while the microscope has been

around since the 16th century

the high-speed video camera has only

been used to study biology for the past

20 years

this is due to innovations that allow

for the filming in low light conditions

this means that we can film organisms

without frying them

but what this all means is that there

are a bunch of discoveries yet to be

made

by looking at the world to the lens of a

high-speed camera today i’m going to

share with you some of these discoveries

as a member of the paddock lab i was

able to be a part of a project that

looked at the jumps

from the larva of a fly specifically the

gall midge fly

you can view these larva as squishy

grains of rice that curl up then rapidly

uncurl

to fling themselves into the air here’s

a video from my colleague’s paper

showing their jumps

in the second video i’m going to show

you a more close-up video of this

take-off sequence

now this entire take-off sequence only

lasts one millisecond

just for comparison the average blink of

an eye lasts anywhere between 100 to 150

milliseconds

literally blink and you’ll miss this

incredible motion

but this time microscope is not only for

animal motions

we can also aim this time microscope at

the plant world

here are some common weeds found in

north carolina and other parts of the

united states

in red we have the wood sorrel and in

yellow we have the hairy bitter crest

while seemingly boring at our time

scales we can we can look

at these fruits under the thai

microscope to capture a remarkable event

seed dispersal first i’m going to show

you

uh the seed the seed dispersal of the

hairy bitter crust

fruits with this plant explode showering

the surrounding area

in confetti like seeds the cool thing

about this motion

is that the explosion of one fruit leads

to the explosion of other fruits in the

plant

next i’m going to show you the sea

dispersal mechanism of the wood sorrel

you can view this mechanism this

mechanism reminds me of those small

rubber rubber toys we had when we were

young that you can flip inside out

put in your palm and watch as they pop

into the air in the same way the

membrane surrounding each seed inverts

setting the seeds out here’s what i mean

and in case you didn’t catch those two

there’s one more seed so if you pay

attention to the center of the fruit

you can see one more right there

so again both of these really awesome

motions are

way too fast to be seen by the naked eye

and without the high speed camera we

would have missed them

all the motions i shared with you so far

are examples of ultra fast motions

just so you can appreciate how fast

ultra fast is i’m going to compare them

to some more common examples of fast

organisms

when we think of fast organisms we

usually think of sprinting cheetah

the diving falcon or the swimming

sailfish

let’s compare these fast organisms to

the ultra fast

and i’m going to use a metric called

acceleration acceleration is a

measurement of how long it takes to

speed up

so above these fast organisms we have

the acceleration of a formula one race

car

above this we have the acceleration of a

missile and here is where we begin to

see

the accelerations of ultra-fast

organisms remember that squishy grain of

rice that jumps

that gauntlege larva has takeoff

acceleration similar to that of a

missile

above that we have the accelerations of

seeds shot from the wood sorrel

and above that we have acceleration of a

bullet shot from a gun

now what organism could possibly have

accelerations similar to a bullet shot

from a gun

this is the range of accelerations of

the mandible strikes of a trap triangle

and this is the organism that i wanted

to study

traptor ants are large ants with animals

that they can snap shut at incredible

velocities

here’s a video i took while collecting

these ants in florida

this is taken in real time ant crawls up

the leaf senses my finger

and snaps sending it backwards i’ll play

it one more time

the ant crawls up the leaf senses my

finger snaps and almost seems to

teleport backwards

without the high speed camera we can’t

really see what’s going on here luckily

we can put this motion under the

under the time microscope i’m about to

show you a video that’s

that’s filmed at 210 000 frames per

second

just for reference my iphone’s slow-mo

camera films at only 240 frames per

second

the video i’m about to show you is 800

times slower than the iphone slo-mo

video

and here it is

what i want you to notice is that even

when filming at these incredibly high

frame rates this motion is still pretty

fast

and what i was interested in was what

happens during the impact of one of

these strikes what happens when one of

these mandibles

strikes target such as my finger in the

previous video

the reason why i was interested in these

impacts is that while dr adrian smith

and i were collecting these ants in

florida

we saw these ants use their mandible

strikes against so many different

targets

we saw him use demandable strikes to

pick up small prey items like termites

we use them use their mandible strikes

to pierce the cuticle to subdue large

pre-items like grubs

in this third video my favorite video

you can see an ant go up to a beetle

strike the beetle and fling itself away

another ant goes to the beetle strikes

but anchors itself

another ant goes up the beetle strikes

the beetle and this time pushes it away

from the nest

from these videos you can see ants do

these mandible strikes for predation

for defend for defense to even use these

mandible strikes to jump

here’s a video i took the ant aims

mandibles towards the ground

strikes the ground and flings itself

multiple body lengths into the air

they use these mandible strikes to

escape from the dangerous ant line pits

dug in the sand

here’s a video from that paper

so across all these diverse uses you can

see why i was interested in finding a

way of measuring the impacts across

these different scenarios

for inspiration on how to measure these

impacts let’s look at other

fast biological motions and how

scientists have studied them

i’m going to be comparing these motions

to the blink of an eye

in red we have the contact duration

between a cheetah paw and the ground

during a sprint

this is anywhere between 50 and 80

milliseconds

and this has been measured with a load

plate

next we have the impacts between a

woodpecker beak and a tree

scientists have used a load cell to

measure these impacts

what about a more human example

dangerous uh

impacts between football player helmets

is anywhere between 5.5 to 13

milliseconds

scientists have used accelerometers

placed inside the helmets to measure

these impacts

so where’s the trap joanne strike in all

this

this tiny purple sliver is the duration

of a trap giant strike

at 0.13 milliseconds this has been

measured with a high speed camera as i

showed you a couple slides back

and just for comparison 800 of these

strikes in real time can be played back

to back

in the time it takes to blink but this

wasn’t what i was interested in

what i was interested in was the impact

from one of these strikes which is a

much shorter duration

so in order to put the impact from these

mandible strikes on this graph

we have to call it our magnifying glass

this this this the same purple rectangle

from before

indicating the duration of a trap to ant

strike this yellow sliver

is a duration of a traptor ant strike

impact at 0.005

milliseconds or one frame when filming

at 210

000 frames per second just for

comparison 20 000

of these impacts can be played back to

back in live in real time in the time it

takes to blink

for strikes at this size and this time

scale we really have no device to

measure these

impacts so it seems like our time

microscope has temporarily failed us

so how can we measure something that can

be measured with a high speed camera

the answer is with perseverance and a

little bit of creativity

while i was thinking about this question

all’s filming and striking targets

different targets

here you can see an ant striking a

plastic target the ant strikes the

target

and both the target and the ant are set

in different directions

this motion reminded me of newton’s

cradle a popular dash toy where you lift

one ball up

let it go and the ball hits other balls

in the sequence

in the same way i figured that we could

capture all the energy

released by this ant in that tiny tiny

amount of time

by measuring the target and the ant

after the strike

so all i had to do was mount the ant and

the target from pendulum

this is much easier said than done my

tears on my prototypes in my first

prototype i suspended both the ant

and the target from here it sounds silly

i know but when you consider the mass of

an ant

you need a similarly lightweight and

sturdy string

i just see from this video when the

answer has a target it seems to bob

around and

then turn around too much this wasn’t

too good

next i mounted the ant and the target

from a carbon fiber rod

and while it’s not depicted in this

video uh the carbon fiber rods are

attached to a roller bearing

an air roller or a ball bearing i’ll get

more i’ll get more

uh i’ll talk more about that later you

can see from this strike the ant strikes

the target

and seems to wobble the target seems to

wobble a little bit too much

i think this wobbling is due to too much

friction at the point of rotation so let

me talk more about that

at the point of rotation as i said

earlier i use the ball bearing

ball bearings use small metal balls to

facilitate the motion of the inner part

and the outer part these are found in

skateboards and roller blades

and while they work for rollerblades and

skateboards at the size

size scale of an ant they seem to stick

a little bit too much

so i was a bit stumped here until i

found about these really cool devices

called air bearings this is a video from

the website

instead of using metal balls to

facilitate the motion of the inner part

and the outer part

air bearings use a pocket of air you can

see from this video

that air is fed into this bearing and

allows for almost near frictionless

point of rotation

i incorporate these bearings into my

setup to produce this final setup shown

here

from this setup i was able to get videos

like this that are really smooth and

easy to interpret

in the first video you can see an ant

striker target that is mounted on a

pendulum

and in a second video you can see an ant

strike a target that is stationary

so an added benefit of this setup is

that allows me to test different targets

that i can swap out

so why build a pendulum for ants again

remember earlier i said that chapter

ants use their mandible strikes in so

many different ways

in a way i kind of view these animals

mandible strikes as a sort of multi-tool

they use these strikes to strike small

squishy targets to strike large squishy

targets

to strike large immovable targets like

the ground

and even weird substrates like sand

before this device we had no real way of

measuring these impacts across these

different scenarios at this size and

time scale

however with my pendrive setup we are

now equipped to find the pros and cons

of using lightweight high acceleration

impacts

so today i only share with you one

discovery to be made by looking at the

world through the lens of a high speed

camera

but remember earlier i said that there

are so many discoveries to be made still

for example here are some videos from

from the lab that i didn’t even get to

show you today

behind each of these videos is a story

similar to mine of curiosity

and discovery these videos span fungi

plants and animals so i hope from this

talk

you can understand why i’m so excited

for discoveries yet to be made by

looking at the world through the lens of

a high-speed camera

thank you

you