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. [♪ INTRO]  The phrase “surface-level”  usually means something… at  least mildly insulting.

If something’s surface-level,   it’s superficial. It’s not interesting.  Well, there’s an entire field  of science that begs to differ.  It’s the science of coating a  thing with another thing, and  making that thing do something wildly different.

These coatings are called monolayers, because each  layer of the material is just  a single molecule thick, spread  out over a surface.  Coating glass with certain  monolayers can make it easier,  not harder, to see through,  and that’s just the start. From  TVs to pacemakers, from  engineering microscopic circuits  to studying and controlling the  behavior of cells, we’re here  today to show that surfaces  are more than skin-deep.  Some optical, electrical and  even biological processes  are easier to deal with on  thin surfaces than they are in  big, bulky volumes. Think about painting   complicated designs on a canvas compared to sculpting   something in the round.

You can more easily manipulate stuff on a   flat plane than in big blobs.  That’s true even for tiny  stuff, and layers can be a great  way to manipulate things down  to the scale of nanometers.  Scientists first got a handle  on monolayers in the early 20th  century, after noticing that  certain kinds of glass actually  transmitted more light when they were tarnished. It all comes down to how light waves transmit   and reflect off surfaces.  If a wave of light heads  straight towards a pane of glass,  most of it will go through  the material, but some small  amount will also be reflected  back. That reflected light  makes up the glare that can  make it harder to see through.  One way of dealing with this  is with a film.

As in a thin  layer of material rather than  the theatrical movie kind,  although we’ll come to those in a moment too! If you put a transparent film with   precisely the right refractive index and   width on the glass, it lets incoming light enter the material as normal,   but it has another effect as well.  Light will be reflected from  the surface of the glass like  before, but it will also be  reflected from the surface of the  film. That sounds like it   ought to increase the total amount of reflected light, making things worse.  But this is the part where we  remember that light is a wave,  with peaks and troughs.

If the  film is just the right width,  the peaks and troughs of the  reflected light from the glass  and the film interfere and align to cancel out! In short, the film actually winds   up with getting rid of the reflections and reducing the   glare, which makes the glass super clear and transparent.  Sounds convenient, but creating  these films isn’t easy.  That was the problem facing  scientists around the 1930s.  Enter star physicist Katherine  Blodgett. Building on the  work of her mentor Irving  Langmuir, she developed a  process involving a chemical  reaction between acids and  other compounds inside a container.

After the reaction, a film would   form on top of the liquid solution, consisting of a thin   layer of something called cadmium arachidate.  This is a type of molecule  with one end that dissolves  readily in water, and one that  doesn’t. Blodgett’s process  lined them all up neatly across  the water, all pointing the  same direction, since the  water-loving ends would end up  facing the water’s surface. If a piece of glass was dunked   into this water beforehand, you could carefully pull it out   so that the film, just a single molecule wide, neatly transfers   itself onto the glass.

Kind of like pulling   out a strawberry from a pot of melted chocolate so it's all coated evenly.  After that, voila, you’ve got  yourself a layer of molecules on  a piece of glass. The resulting films are called Langmuir-Blodgett  monolayers, or LBMs, named  after their inventors. The  specialized container used  for creating them is called a  Langmuir-Blodgett trough.

The trough, along with the   method they used for lifting monolayers out intact,   is what allowed them to apply LBMs onto solid surfaces, like glass.  By repeating this process as  many times as needed to get  the right thickness, Blodgett  managed to create a film of  material on glass capable  of reflecting less than one  percent of white light falling on it. That made the glass amazingly clear   and was extremely useful. For example,   glass developed using her process produced crystal clear lenses used   for movie projectors in the late 1930s.  The same kind of lenses were  even used in the periscopes  built for submarines and spy  planes in the second world  war!

But Blodgett   and Lamguir’s research on monolayers wasn’t just confined to glass, or even a particular   chemical process.  Using Langmuir-Blodgett  troughs with different chemical  reactions, researchers could  apply even, molecule-sized  layers onto materials for all  kinds of uses. Basically, a kind  of Swiss army knife of nano-scale engineering! For instance, you might be   familiar with OLED TVs or computer monitors.

They use organic light emitting  diodes to create a picture.  But they’re pretty inefficient,  especially the blue kind. Because of the crystal   structure inside the OLED, the light kind of bounces around inside it   before escaping, getting absorbed by the material   and losing energy instead of coming out as visible light.  But if we could control the  thickness, pattern and shape of  the OLED layers, we might  be able to make them more  efficient at releasing light. A 2016 study by French researchers found that  constructing these layers  with LBMs did make them super  efficient, and that by carefully  tweaking the different layers,  they could even understand why.

Which means LBMs could   help us save energy when using those big old screens we like looking at so much.  But as incredible as LBMs  are, they’re not always the  best way of neatly arranging  a layer of molecules onto a  surface. In some cases,   they’re chemically unstable on the surface  they’re applied to, meaning  they won’t stick around in their  organized, layered structure  for long. And what’s more,  using a Langmuir-Blodgett trough can be a slow and delicate process.  It only works on flat surfaces,  and it’s one and done.

No  tweaking once you’ve pulled your surface out. But, as is often the case in chemistry,   there’s more than one way to arrange an   organized layer of molecules onto a surface. You know, as they say.  By 1946, chemists had seen  that in some cases they could  simply dunk a surface into  a solution, and have the  molecules arrange themselves  onto it in a neat layer.  In 1980 chemist Jacob Sagiv,  at the Max Planck Institute in  Germany, showed that it was possible to create monolayers on certain kinds of   surfaces without all that messing around with a water trough.  In Sagiv’s version, the  molecules in the solution were  individually attracted onto  the solid surface, sticking  themselves onto it in a  particular direction.

In a short  amount of time, they arranged themselves into a monolayer, firmly stuck onto the material.  In fact, by mixing and  matching specific molecules and  organizing different surfaces,  it was possible to create  patterns – something you couldn’t get with the pull-out-the-strawberry method.  Since these monolayers  assemble themselves, they’re  called, no awards for guessing, self-assembled monolayers or SAMs.  Sagiv’s work on SAMs was a  huge step, allowing him to  create monolayers on a variety  of surfaces. Specifically,  solids with a layer of  oxides on their surfaces were  especially well suited to the process. That might seem super specific,   but lots of materials exposed to air react   with oxygen and end up with oxides on their surface, so the ability   to make SAMs on them opens a lot of doors.  For example, this made it  possible to make electrical  circuits at the nano-scale,  as in, technology that’s only  dozens of molecules or so in size.

Using SAMs, Sagiv was able to create   monolayers that could conduct   currents through them, which is a crucial step for engineering electrical circuits   that are only a few molecules thick!  Which you’d want for things  like transparent displays or  smart contact lenses – things  where you don’t want the  electronics getting in the way. But while this works for   things like electronics, SAMs would have even more potential if they could be put onto  materials without oxides,  like bare metal surfaces.  A few years later in 1983,  the chemists Ralph Nuzzo and  David Allara reported in  the Journal of the American  Chemical Society that they’d  created a SAM on a surface  of bare gold. These kinds of SAMs   were a game changer.

Like Blodgett and Langmuir had shown forty years   earlier, covering the surface of a thing with   something else can vastly change what you can do with that thing.  The SAMs based on Nuzzo and  Allara’s design could be  made from lots of different  organic materials and made as  precise as a few atoms in width. Researchers have since used them to change the  electrical properties of  metals, make them more resistant  to corrosion, and in particular,  study biological processes.  See, long before humans got into the molecular engineering game, nature was chock-full   of microbiological processes carrying out   different functions at the nanoscale. And a lot of these happen at some   kind of boundary, like the surface of a cell.  Which makes SAMs a great model system for studying such processes.  For instance, in one 1991  study, German researchers  embedded molecules of biotin  onto an SAM, which itself  was bonded onto gold.

In  nature, biotin has particularly  strong reactions with a protein  called streptavidin, that  plays a key role in biochemical processes. The SAM basically gave the researchers a nanoscale  hotbed for studying the chemical  interactions between the  two in a well-controlled way! As well as studying nature,   researchers also quickly realized they could use the   microbiological tools it provided.  One instance is what’s called  a DNA microarray.

These  are a sort of fancy chip with  a lot of DNA stuck on them.  Since a strand of DNA will  connect with its complementary  strand, a microarray can tell you how much of that complementary DNA is present in a given sample.  Like, the level of certain  genes expressed in samples from  patients who do or don’t have  a particular sort of cancer  can be very different, and so  a DNA array can be a kind of  genetic magnifying glass  to help diagnose a patient.  Early on, SAMs were a promising way of creating microarrays like these because   they could be used to hold a bunch of molecules, like DNA, in place.  The challenge was placing each strand of DNA in a particular location on the array,   since you have to know what location on the chip corresponds to what DNA  sequence. Which meant finding  a way of creating SAMs  with specific and intricate patterns. By 1992, a team of Harvard   researchers led by the chemist George Whitesides had cracked   the problem using what’s called soft lithography.  The solution was basically  drawing a particular pattern  onto gold with the substance  that the SAM would be made  out of.

That laid the   foundation for another idea. Instead of drawing it out, they created the pattern   they wanted on a kind of stamp,   covered it in the substance the monolayer would be made of and stamped it on a surface   to create an SAM.  Later, Whitesides’ team  came up with another way to  achieve the same effect, only  this time, the idea was to  make a kind of mold in the  shape of the film you wanted to  create and put it on top of a  surface, like gold, and fill it  with the substance of the film. After a short while,   remove the mold and you’ve got yourself an SAM with a particular shape!  There’s a lot going on here,  so to recap, by controlling the  exact shape and structure of a SAM, we can create surfaces which hold specific   biological molecules in place.

That makes it easier to study them,   but also to use them, like in a DNA array.  Better still, SAMs made with  particular patterns can hold all  kinds of useful and important  molecules on surfaces.  Pacemakers, for instance,  can often be attacked by the  body at the point where the  electrical contacts are in touch  with your organs, because the  immune system identifies it  as something foreign to the body. And the resulting inflammation does a   lot more harm than good.  But, by coating the contact  points with SAMs, they can be  cloaked with anti-inflammatory  molecules that prevent the  body from going haywire. A little like an   invisibility cloak for medical equipment.

Nothing to see here, just normal heart things.  I could keep going, but  hopefully you’ve seen that the  ability to stick a thing to a  surface has an incredible range  of applications from medical devices to consumer  electronics. In 2022 Sagiv, Nuzzo,   Allara and Whitsides were all awarded the Kavli Prize in   Nanoscience for the remarkable tools they worked to develop in   creating and studying SAMs.  At the time of this video,  there are already ten thousand  patents involving SAMs, from  chemical sensors to solar  cells. So at least on the   nanoscale, we’ve only begun to scratch the surface… or at least build on it.  Thanks to the Kavli Prize  Foundation for partnering with us  on this video.

The Kavli  Prize honors scientists for  breakthroughs in astrophysics, nanoscience and neuroscience, transforming our   understanding of the big, the small and the complex.  Now that you’ve learned  about the nanoscience award,  you can check out the research  that earned a 2022 Kavli  Prize in neuroscience and astrophysics. [♪ OUTRO]