Can you guess what you’re looking at?
Is it a fuzzy sock?
An overripe banana?
A moldy tube of toothpaste?
In fact, this is the humble sea cucumber, and while it might look odd, its daily toil paves the way for entire ecosystems to thrive.
Sea cucumbers are members of the phylum Echinodermata, along with sea urchins, starfish and other radially symmetrical, “spiny-skinned” marine invertebrates.
Some sea cucumbers have feathery tentacles flowing from their mouths, some are puffed like bloated balloons, and others simply look like Headless Chicken Monsters— the actual name given to a rare deep-sea species.
But they are generally characterized by their long, cylindrical shape.
A sea cucumber is essentially a brainless, fleshy form surrounding a digestive tract, bookended by a mouth and an anus.
Adhesive tube feet run the length of their bodies and allow them to scoot along the seafloor.
Specialized tube feet can be used for feeding and respiration, though many sea cucumbers actually breathe through their anuses.
Rhythmically contracting and relaxing their muscles, they draw water in and out over an internal lung-like structure called a respiratory tree that extracts oxygen from seawater.
Certain species of crabs and pearlfish take advantage of this rhythmic action and, once the sea cucumber’s anus is dilated, they shimmy in and take shelter.
The rear end of a single sea cucumber can harbor up to fifteen pearlfish at a time.
However, it seems that not all sea cucumbers put up with this intrusive behavior.
Some species are equipped with five teeth around their anus, suggesting that they may have taken an evolutionary stand against unwanted guests.
But even sea cucumbers that lack anal teeth are outfitted with tools to defend themselves.
They evade threats and launch counter-attacks using their mutable collagenous tissue, or MCT.
This gel-like tissue contains bundles of collagen, called “fibrils.”
Proteins can interact with these fibrils to slide them together, stiffening the tissue, or apart, softening it.
This versatile tissue has many advantages: it aids in efficient locomotion, enables sea cucumbers to fit into small spaces, and allows them to reproduce asexually by splitting apart.
But MCT’s most explosive application is employed when a predator attacks.
By loosening the attachments of internal tissues then quickly softening and contracting their muscles, many species are capable of shooting a wide range of organs out of their anuses.
This act is called “evisceration” and it’s a surprisingly effective defense mechanism.
In addition to startling and distracting predators, the innards of some sea cucumber species are sticky and toxic.
Evisceration may seem drastic, but sea cucumbers are able to regenerate what they’ve lost to their gut reaction in just a few weeks’ time.
Aside from the few species that have evolved to swim and those that feed without moving, many of these cumbersome creatures pass their time grazing the seabed.
Sea cucumbers are found everywhere from shallow shores to abyssal trenches 6,000 meters below sea level.
On the deep sea floor, they comprise the majority of animal biomass, reaching up to 95% in some areas.
As these sausage-shaped wonders trudge along, they vacuum up sand, digest the organic matter it contains, and excrete the byproduct.
In this process, sea cucumbers clean and oxygenate the seafloor by breaking down detritus and recycling nutrients.
This creates the conditions for sea grass beds and shellfish to thrive.
Sea cucumber excretions can also aid in coral formation and may play a role in buffering marine environments from ocean acidification.
As the ocean’s vacuum cleaners, they are very good at their job: about half of the sandy seafloor is thought to have passed through the digestive tract of a sea cucumber.
So next time you’re rejoicing in the feeling of sand crunching between your toes, consider this: those very grains of sand might have, at one point or another, been excreted by a pickle that breathes through its butt.
My students and I work on very tiny robots.
Now, you can think of these as robotic versions of something that you're all very familiar with: an ant.
We all know that ants and other insects at this size scale can do some pretty incredible things.
We've all seen a group of ants, or some version of that, carting off your potato chip at a picnic, for example.
But what are the real challenges of engineering these ants?
Well, first of all, how do we get the capabilities of an ant in a robot at the same size scale?
Well, first we need to figure out how to make them move when they're so small.
We need mechanisms like legs and efficient motors in order to support that locomotion, and we need the sensors, power and control in order to pull everything together in a semi-intelligent ant robot.
And finally, to make these things really functional, we want a lot of them working together in order to do bigger things.
So I'll start with mobility.
Insects move around amazingly well.
This video is from UC Berkeley.
It shows a cockroach moving over incredibly rough terrain without tipping over, and it's able to do this because its legs are a combination of rigid materials, which is what we traditionally use to make robots, and soft materials.
Jumping is another really interesting way to get around when you're very small.
So these insects store energy in a spring and release that really quickly to get the high power they need to jump out of water, for example.
So one of the big contributions from my lab has been to combine rigid and soft materials in very, very small mechanisms.
So this jumping mechanism is about four millimeters on a side, so really tiny.
The hard material here is silicon, and the soft material is silicone rubber.
And the basic idea is that we're going to compress this, store energy in the springs, and then release it to jump.
So there's no motors on board this right now, no power.
This is actuated with a method that we call in my lab "graduate student with tweezers."
(Laughter) So what you'll see in the next video is this guy doing amazingly well for its jumps.
So this is Aaron, the graduate student in question, with the tweezers, and what you see is this four-millimeter-sized mechanism jumping almost 40 centimeters high.
That's almost 100 times its own length.
And it survives, bounces on the table, it's incredibly robust, and of course survives quite well until we lose it because it's very tiny.
Ultimately, though, we want to add motors to this too, and we have students in the lab working on millimeter-sized motors to eventually integrate onto small, autonomous robots.
But in order to look at mobility and locomotion at this size scale to start, we're cheating and using magnets.
So this shows what would eventually be part of a micro-robot leg, and you can see the silicone rubber joints and there's an embedded magnet that's being moved around by an external magnetic field.
So this leads to the robot that I showed you earlier.
The really interesting thing that this robot can help us figure out is how insects move at this scale.
We have a really good model for how everything from a cockroach up to an elephant moves.
We all move in this kind of bouncy way when we run.
But when I'm really small, the forces between my feet and the ground are going to affect my locomotion a lot more than my mass, which is what causes that bouncy motion.
So this guy doesn't work quite yet, but we do have slightly larger versions that do run around.
So this is about a centimeter cubed, a centimeter on a side, so very tiny, and we've gotten this to run about 10 body lengths per second, so 10 centimeters per second.
It's pretty quick for a little, small guy, and that's really only limited by our test setup.
But this gives you some idea of how it works right now.
We can also make 3D-printed versions of this that can climb over obstacles, a lot like the cockroach that you saw earlier.
But ultimately we want to add everything onboard the robot.
We want sensing, power, control, actuation all together, and not everything needs to be bio-inspired.
So this robot's about the size of a Tic Tac.
And in this case, instead of magnets or muscles to move this around, we use rockets.
So this is a micro-fabricated energetic material, and we can create tiny pixels of this, and we can put one of these pixels on the belly of this robot, and this robot, then, is going to jump when it senses an increase in light.
So the next video is one of my favorites.
So you have this 300-milligram robot jumping about eight centimeters in the air.
It's only four by four by seven millimeters in size.
And you'll see a big flash at the beginning when the energetic is set off, and the robot tumbling through the air.
So there was that big flash, and you can see the robot jumping up through the air.
So there's no tethers on this, no wires connecting to this.
Everything is onboard, and it jumped in response to the student just flicking on a desk lamp next to it.
So I think you can imagine all the cool things that we could do with robots that can run and crawl and jump and roll at this size scale.
Imagine the rubble that you get after a natural disaster like an earthquake.
Imagine these small robots running through that rubble to look for survivors.
Or imagine a lot of small robots running around a bridge in order to inspect it and make sure it's safe so you don't get collapses like this, which happened outside of Minneapolis in 2007.
Or just imagine what you could do if you had robots that could swim through your blood.
Right?
"Fantastic Voyage," Isaac Asimov.
Or they could operate without having to cut you open in the first place.
Or we could radically change the way we build things if we have our tiny robots work the same way that termites do, and they build these incredible eight-meter-high mounds, effectively well ventilated apartment buildings for other termites in Africa and Australia.
So I think I've given you some of the possibilities of what we can do with these small robots.
And we've made some advances so far, but there's still a long way to go, and hopefully some of you can contribute to that destination.
Thanks very much.
(Applause)