This episode was made in partnership with The Kavli Prize.
The Kavli Prize honors scientists for breakthroughs in astrophysics, nanoscience,
and neuroscience – transforming our understanding of the big,
the small, and the complex.
There’s an old proverb in science: we make progress
by standing on the shoulders of giants.
It means that science advances by building on the work of those who came before.
Sometimes, a researcher will spend their career doing important foundational work
that paves the way for countless others to make exciting discoveries decades later.
One such ‘giant’ is Mildred Dresselhaus,
who in 2012 was honored with the Kavli Prize in Nanoscience.
She didn’t invent self-charging phones,
improve solar cells, or make a better refrigerator.
But she has made it possible for somebody else to.
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Before she was Professor Dresselhaus, giant in the field of nanoscience,
she was Millie Spiewak, born in New York in 1930.
She attended Hunter College in New York, where her talent was recognized
by her physics teacher, the future Nobel laureate Rosalyn Yalow.
Yalow mentored Mildred for many years.
Mildred then went on to study at Cambridge University and
the University of Chicago under the superstar physicist Enrico Fermi.
In 1960, after becoming Dr Dresselhaus, she left her PhD work on
superconductors, and started her pioneering work on carbon at MIT.
She’d married fellow physicist Gene Dresselhaus,
and they chose MIT as it was the only place that would hire partners together.
It worked out for her, though, because she stayed there for almost 60 years,
becoming the first woman to reach MIT’s highest rank of Institute Professor.
During that time she made huge strides in the study of nanomaterials,
which are materials that incorporate nanoparticles,
or structures that have only a few dozen or hundred atoms.
For comparison, a human body has about a billion billion billion atoms!
In the 1970s, Dresselhaus was one of the first people to study graphene,
which is a two-dimensional form of graphite, the kind of carbon in plain old pencils.
It sounds bizarre to call any kind of real-life thing 2D, because the real world is 3D.
But we think like this all the time.
Paper isn’t really 2D, but we can treat it like it is;
we ignore its third dimension for practical purposes.
Likewise, graphene is only one layer of carbon atoms thick.
So it makes sense to pretend it’s 2D.
What Dr. Dresselhaus and others worked out is that for nanomaterials like this,
when their dimension changes, like from 3D to 2D,
their properties can change drastically as well.
And she’d use that insight time and time again in her career.
See, carbon is a shapeshifter.
Diamond, graphite, and graphene are all made of carbon atoms in different
arrangements, but their properties couldn’t be any more different.
It’s now known that graphene could be used to make electricity-conducting,
heat-resistant plastics, next-generation transistors for computers, and lots more.
But Dr. Dresselhaus wasn’t content with just one amazing carbon discovery.
So in the 1980s, she pivoted to another weird form of carbon:
buckminsterfullerene, or buckyballs if you’re feeling silly.
These are nano-sized spheres of just 60 carbon atoms,
arranged like the shapes on soccer balls.
It’s thought that they may be useful for many things, like targeted drug delivery.
The ball of carbon could contain molecules
of a drug and release them at specific locations in the body.
And once again, Mildred Dresselhaus was
one of the first to discover and study these tiny spheres.
She found them coming off of graphite when she fired lasers at it.
Both graphene and buckyballs would later go on to have Nobel Prizes awarded
for their discoveries, and Dresselhaus laid the
important groundwork for both of them.
Then in the 90s, she had an idea to reduce
the dimension of carbon even further: down to 1D.
Her idea was to take buckyballs and ‘stretch’ them out
by adding more carbon atoms.
She worked out that if a cylinder of buckyball-like carbon structures
was long enough, you could treat the tube as 1D;
its length would matter way more than its other dimensions.
This was the carbon nanotube, and she was one of its early pioneers in the 1990s.
She showed that depending on how it’s made,
it can be either semiconducting or metallic.
Meaning that the same element that makes diamonds and pencils can potentially
act like a metal, with the ability to hold up unbelievable weights without breaking.
For all of this, she’s been nicknamed the ‘Queen of Carbon Science’,
but amazingly, it’s not her work on carbon that earned her the Kavli Prize.
In the late 90s, she moved onto an entirely
new research area, and revolutionized that, too.
Her later work was on the so-called thermoelectric effect,
where materials convert residual heat into electricity.
Once again, Dresselhaus’s contribution was to realize that some materials have
very different thermoelectric properties
when they’re made of 2D sheets or 1D strings.
The reason for this is that electrons in materials can only have certain specific
amounts of energy, and if one energy level is occupied,
no other electron can occupy it.
This was something her old mentor Fermi discovered.
Plus, electrons also want to have as low an energy as possible,
so they’ll fill all available energy levels from the bottom up.
But in 1D and 2D, the distribution of energy levels is different,
so that when electrons fill them, it changes the properties of the material.
The electrons are forced to reconfigure themselves.
Dresselhaus showed that this could change how well
the material converted heat by a factor of ten.
And on top of that, she found out that being in 1D and 2D
also changed how particles of heat bounced off the material.
Except… heat doesn’t come in particle form, does it?
You may know that light has a fundamental particle called the photon.
Well, there is also a sort of quasiparticle called
the phonon that acts like a particle of heat.
See, particles jiggle when they’re hot, and bump into other particles.
That bumping can transfer the ‘jiggle’ energy, AKA heat.
This process actually behaves very similarly to how materials
emit and absorb light; by producing and consuming photons.
So it actually makes sense to say that materials produce and
consume phonons of heat energy, too.
Even though they’re not real particles,
they simplify things and help our understanding.
And what Dresselhaus showed was that in 1D and 2D,
electrons and phonons interact very differently compared to how they do in 3D.
The phonons are affected by the lower dimension.
And that insight allows for the production of more efficient thermoelectric materials.
So while it won’t exactly solve the energy crisis any time soon,
Dresselhaus’s thermoelectric breakthrough could
pave the way for some clever compact, self-powered devices.
You may one day be able to charge your phone
just from the warmth of keeping it in your pocket.
In 2012, Dr. Dresselhaus was the first person to be
awarded an individual Kavli Prize for nanoscience.
It was given “For her pioneering contributions to the study of phonons,
electron-phonon interactions, and thermal transport in nanostructures.”
And her career didn’t even end there.
Dresselhaus worked well into her 80s before passing away in 2017.
During her amazing career, she received countless awards,
including the prestigious Kavli prize, and the Presidential Medal of Freedom.
It’s safe to say this “one in a Millie” scientist
left a giant footprint in the world of the very small.
Thanks for watching this episode of SciShow!
And thank you again to The Kavli Prize for supporting this episode.
The Kavli Prize in Nanoscience is awarded for outstanding achievement in
advancing our understanding of atomic, molecular and cellular structures.
They also award a neuroscience and astrophysics prize,
honoring researchers for transforming our understanding
of the brain and nervous system, and advancing our knowledge of the origin,
evolution and properties of the universe.
If you want to learn more about Dr. Dresselhaus’ work, you can visit her page
on the Kavli Prize website by clicking the link in the description.
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