So, imagine you had a bag of programmable matter,
by which I mean, engineered modules that cooperate with
each other to form shapes.
You could reach in and pull out some object you needed,
like a wrench or a coffee cup,
And then when you were done with it, you could put it
back into the bag, and it would break apart and its modules
would be available to form the next object that you needed.
So, biology provides the inspiration that this is, in fact, possible.
This is a simulation by my colleague Jonathan Bachrach,
showing a mechanical protein folding itself into several objects.
This is a chain of engineered modules, and each module
has a motor that can exert a force on its joint.
By setting the angle on each joint, it's possible to fold the representation of any shape.
Although, in practice I think you'd want to have lots of these chains
working together, just like biology does it.
We had a grant from DARPA to build a prototype of this,
and the grant had a requirement that the modules be smaller
than one cubic centimeter. And, because we wanted to
make a lot of these modules, we wanted the modules to be
cheap and simple, and so we decided to not use gearing,
just to have the motor directly drive each axis.
We looked, but we couldn't find any off-the-shelf motors
that were small enough, and could exert enough continuous force,
without burning themselves out.
So we invented a new type of motor, which we call
an electropermanent motor.
This motor works by using coils to remagnetize its permanent magnets
all the way around their hysteresis loops on every step.
What this means is, when you remove power, the device holds its position,
and it can exert its maximum force with very low average power input.
Once we had the motor working, we designed the rest of
the mechanical protein. It's basically a chain of motor rotors and stators,
the rotating part and the stationary parts — interlocked together,
with a flexible circuit wrapped around it for power and control.
We had to learn watchmaking techniques to build the prototypes, which was fun.
So, here's a video, probably taken at about 2am, of the
first module turning in a pair of scissors on my desk.
You'll see the coiled portion of the flexible circuit coiling and uncoiling
to connect the module to its neighbor; it took us a while to get that right.
And then once we had one module working we made four more;
here is a chain forming shapes. It starts out as a line, and then it forms:
a left handed helix
a right handed helix
a periscope
and an L-shape.
Every module gets its instructions to turn left, right, or straight;
that's like the DNA code for the shape,
and then the motors fold the chain up into the shape.
The motors are strong enough to lift one other segment, which is OK, it works,
but to have performance on par with geared systems,
we'd like to be able to lift 2-3 other modules,
which we think we can get to with a lighter structure and with better materials.
Still, as far as we know this is the highest resolution
chain-type programmable matter system built to date.
We started this project with a vision of programmable matter,
but we ended up inventing a motor that can hold its position without power.
We're still working on programmable matter, of course,
but working with our industrial partners, we've discovered
that there are a lot of applications for such a small, low-power motor,
in aerospace and medical applications, and so we're working with them now
to push this technology out into the world.