In a previous video I've spoken about one of the many challenges that lie behind designing
drones that are smaller than this, and one of the main ones is having batteries that
are able to power something this small for a signicant amount of time. And today I'm
going to be sharing with you a really nifty -but also quite creepy- bit of research which
has managed to circumvent its way around this problem.
Remote controlled insects!
So... how do they do it?
[INTRO by Caro Waro & Cristina de Manuel]
Step 1: Choose your victim
I was initially very surprised to see that they'd chosen a beetle to do this research
with, mainly because they're not really the most adept fliers and they're also not
one of the model organisms of insect flight. Normally you'll find studies done on locusts,
hawkmoths, flies and bumblebees. But when put into context it makes perfect sense that
they chose the beetles, because in order to carry the gear that will control the insect,
they require one that is large enough to carry it and also able to carry a load - and it
turns out that large beetles are the only ones out there that fit the bill.
Step 2: Choose your gear
So you've got your insect, now you have to put the gear onto it. At first they started
to work with Cotinis texana, the Texan Green June Bug, at 1.5cm and able to carry about
30% of its weight it was just large enough to be able to carry the microprocessor and
the electrodes, but not quite enough to carry the radio. So this meant that they actually
had pre-programmed in-flight commands that they sent to the insect but they weren't able
to send it to it in real time. So the researchers then made an upgrade to
Mecynorrhina torquata, which is considerably larger - it's actually, I think, the second
largest beetle in the world, only behind Mecynorrhina torquata ugandensis, the African Goliath beetle.
And this one was definitely able to carry the radio controller.
Step 3: You've got to make it fly! So you've got your insect, you've got your
gear, here comes the tricky bit - you have to make it do something. From the literature
and from previous studies into insect flight we actually know a lot about what triggers
insect flight - there are lots of natural cues such as looming shapes towards flies
or blowing on the sensory hair cells on locust's face which will make them initiate flight.
Electrophysiological studies which involve the placement of electrodes to monitor the
neural signals sent by different muscles and neurons also let us know a lot about what
triggers insect flight. So the next step from there is to be able
to relay a signal onto the insect. The researchers wanted it to target a very general area of
the insect's brain, because obviously, when you're flying, the electrode is probably going
to be moving around, so you don't want to be targeting a highly specific neuronal pathway.
And they also wanted to make sure it was a signal that would override what the insect
was normally doing but without causing harm to it. And they found a region inside the
optic lobe in the insect's brain which when triggered would cause it to start flight.
That was when it was provided with lots of short pulses, and when they gave it a longer
pulse it actually overloaded that area so the signal would stop propagating and this
caused the insect to stop flying. And in fact, they found that if they delivered lots of
on-off pulses to the insect they were able to control the thrust of it.
Step four - make it turn. You've got your insect, it flies, you can
also control how far up and down it goes but obviously you want to be able to control it
and give it a bit of direction, so the next logical step from there is to make it turn.
The researchers didn't find a specific pathway in the brain to make it turn reliably - so
they took a different approach and they actually directly targeted one of the direct flight
muscles known as the basalar muscle.
At this point, I'm going to go on a quick tangent to give you a very brief explanation
of how insects fly, specifically beetles. I did mention earlier that beetles aren't
really the most adept of fliers, but they do have one of the most refined flying systems
out of the insects. First of all, they have both indirect and direct flight muscles. Indirect
flight muscles are muscles that don't directly connect to the wings, they are actually attached
to the thorax, there are two perpendicular sets - some that attach from the top to the
bottom of the thorax and some from the front of the thorax to the back. And these contract
in a coordinated manner and cause the thorax to deform. Because the wings are essentially
extensions of the thorax, these flap along with it. The other thing about these indirect
flight muscles is that they are asynchronous flight muscles. What this means is that a
single neural signal from the brain causes the muscles to contract
repeatedly, so rather than having a very low wing beat frequency they can achieve much
faster ones and also don't require as much neuronal input from the brain. The direct
flight muscles are muscles that connect directly to the wing (base) and in the case of beetles
and many insects that have both indirect and direct flight muscles the role of the direct
flight muscles is simply to fine-tune and adjust the positioning of the wings, so they're
able to do the different manouevres they do - and one of those direct flight muscles is
the basalar muscle, and they found - when for instance, they would target the left basalar
muscle, the left wing would flap much more powerfully and the insect would steer to the
right. The thing is, this was actually a very crude
way of doing it and they still didn't have the hugest degree of control over how the
beetle flew. So quite recently, they made a very exciting recent development where they
discovered that another one of the direct flight muscles, which is the third axiliary
muscle is one that's directly involving in steering in beetles. It's still not perfect,
but they're much better at being able to make graded turns with the beetles now.
Step 5 - make it walk So you've got your beetle, you can pretty
much make it fly, take off, go up/down, turn left and right, the system's pretty crude
but it's still a very impressive feat of engineering. What's left is to make it walk - and in a
very recent study, they have found the way to do that. The beetle's leg has three sets of muscle pairs
they could control, which when stimulated, allow the leg to move in different manners. The first one is the
protraction and retraction, found inside the insect's prothorax and they control how well the beetle is able to
retract and protract its legs. Within the coxa you've
got muscles that control levation and depression, essentially how does it lift or put down its
leg, and finally, within the femur, it's got extensor and flexor muscles which basically
cause the tibia to extend or flex. And by controlling all six of these muscles at once
they're able to make the beetles walk in different gaits and follow different patterns, which
I think is incredibly impressive.
Step 6: world domination!
So you've got your flying insects, you can save the world - or conquer the world, do
whatever you want with your Frankenbeetles. I'm getting a little bit carried away, and
I am kind of joking, but I will have you know that there are a lot of remote controlled
animals out there, they've done it with moths, they've done it with cockroaches which I think
are commercially available, and they've also done it with rats with this technique known
as optogenetics.
Anyway, I really hope you're having a very happy and horrific Halloween and that you've
enjoyed this Draw Curiosity Halloween special - huge thank you to the researchers Professor
Maharbiz and Hirotaka Sato who have kindly lent me the footage that you've seen
in this video and they are also the people behind the amazing research I've been talking
about. If you liked this type of video where I talk about insect flight, which is my speciality,
and also I just generally have a huge passion for insects, then let me know, because I can
definitely make more videos like this - and as always thank you so much for watching me
and I'll see you in the next one! Bye!
[Channel Art & Animation: Caro Waro & Cristina de Manuel]
[MUSIC: Thastor & CryoSleepKitten] [Scripting, Hosting, Editing: Inés Dawson]
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