A new way to "grow" islands and coastlines

For nearly a decade,

my collaborators and I
at the Self-Assembly Lab

have been working on material systems
that transform themselves,

assemble themselves,

and adapt to their environment.

From our early work on 4D printing,

where we printed objects,
dipped them underwater,

and they transform,

to our active auxetics that respond
to temperature and sunlight,

to our more recent work on active textiles

that respond to body temperature
and change porosity,

to our rapid liquid printing work

where we print inflatable structures

that morph based on air pressure

and go from one shape to another,

or our self-assembly work

where we dip objects underwater,

they respond to wave energy
and assemble themselves

into precise objects like furniture.

Or, at larger scales,

using wind energy,

we have meter-diameter weather balloons

that assemble in the airspace
above a construction site.

For dangerous environments
or harsh, extreme places

where it's hard to get
people or equipment,

they can assemble in the airspace,
and as the helium dies,

they then come back to the ground,

and you're left with a big
space frame structure.

All of this research is about
taking simple materials,

activating them with forces
in their environment --

gravity, wind, waves,
temperature, sunlight --

and getting them to perform,

getting them to transform, assemble, etc.

How do we build smart things

without complex electromechanical devices?

But more recently, we were approached
by a group in the Maldives,

and they were interested in taking
some of this research and ways of thinking

and applying it to some of
the challenges that they've faced

in terms of climate change.

And the first thing that you do

when you're approached
by someone in the Maldives

is say you want to go on a site visit.

(Laughter)

It is amazing.

So we went there

and I actually walked away
with a really different perspective

on the future of climate change.

Because, you would imagine,
you know, the Maldives are sinking,

they're screwed.

What are they going to do?

But I walked away thinking,
they might actually be the model,

the future model of the built environment,

where they can adapt and be resilient
rather than our fixed,

manmade infrastructure.

But there's typically
three main approaches

to sea level rise and climate change.

One of them is that we can do nothing
and we can run away.

And that's a pretty bad idea.

As more than 40 percent
of the world's population

is living in coastal areas,

as sea levels rise and as storms
get worse and worse,

we're going to be
more and more underwater.

So it's imperative that we solve
this pretty demanding problem.

The second is that we can build barriers.

We can build walls.

The problem here is that
we take a static solution

trying to fight against a super-dynamic,
high-energy problem,

and nature is almost always going to win.

So that's likely not going to work either.

The third approach is using dredging.

So dredging is where you suck up
a bunch of sand from the deep ocean

and you pump it back onto the beaches.

If you go to any beach around
the Northeast or Western Coast,

you'll see that they use dredging
year after year after year

just to survive.

It's really not a good solution.

In the Maldives, they do the same thing,

and they can build an island in a month,

a brand new island
they build from dredging.

But it's really, really bad
for the marine ecosystem,

and then they become addicted to dredging.

They need to do that year after year.

But in the time that it took them
to build that one island,

three sandbars built themselves,

and these are massive amounts of sand

so big you can park your boat on it,

and this is what's called a site visit.

It's really hard work.

(Laughter)

In Boston winters.

This is massive amounts of sand
that naturally accumulates

just based on the forces of the waves

and the ocean topography.

So we started to study that.
Why do sandbars form?

If we could tap into that,
we could understand it

and we could utilize it.

It's based on the amount
of energy in the ocean

and the topography in the landscape
that promotes sand accumulation.

So what we're proposing
is to work with the forces of nature

to build rather to destroy,

and in my lab at MIT,
we set up a wave tank,

a big tank that's pumping waves,

and we placed geometries underwater.

We tried all sorts
of different geometries.

The waves interact with the geometry,

and then create turbulence
and start to accumulate the sand

so the sand starts to form
these sandbars on their own.

Here's an aerial view.

On the lefthand side,
you'll see the beach that's growing.

In the middle you'll see
the sandbar that formed.

So these are geometries that collaborate
with the force of the wave to build.

We then started to fabricate one.
This was in February in Boston.

We have large rolls of canvas.

It's a biodegradable material,

it's super-cheap, easy to work with.

We then sew it into these large bladders,

and then we flew over there.