Sometimes, experimental results spark enormous curiosity inspiring a myriad of questions and ideas for further experimentation. In 2004, Geim and Novoselov, from The University of Manchester, isolated a single layer of graphene from bulk graphite with the “Scotch Tape Method” for which they were awarded the 2010 Nobel Prize in Physics.  This one experimental result has branched out countless times serving as a source of inspiration in as many different fields.  We are now in the midst of an array of branching-out in graphene research, and one of those branches gaining attention is ultra low friction observed between graphene and other surface materials.  

Much has been learned about graphene in the past 15 years through an immense amount of research, most of which, in non-mechanical realms (e.g., electron transport measurements, thermal conductivity, pseudo magnetic fields in strain engineering).  However, superlubricity, a mechanical phenomenon, has become the focus among many research groups. Mechanical measurements have famously shown graphene’s tensile strength to be hundreds of times that of the strongest steel, indisputably placing it atop the list of construction materials best for a superhero suit.  Superlubricity is a tribological property of graphene and is, arguably, as equally impressive as graphene’s tensile strength.

Tribology is the study of interacting surfaces during relative motion including sources of friction and methods for its reduction.  It’s not a recent discovery that coating a surface with graphite (many layers of graphene) can lower friction between two sliding surfaces.  Current research studies the precise mechanisms and surfaces for which to minimize friction with single or several layers of graphene. 

Research published in Nature Materials in 2018 measures friction between surfaces under constant load and velocity. The experiment includes two groups; one consisting of two graphene surfaces (homogeneous junction), and another consisting of graphene and hexagonal boron nitride (heterogeneous junction).   The research group measures friction using Atomic Force Microscopy (AFM).  The hexagonal boron nitride (or graphene for a homogeneous junction) is fixed to the stage of the AFM while the graphene slides atop.  Loads are held constant at 20 𝜇N and sliding velocity constant at 200 nm/s. Ultra low friction is observed for homogeneous junctions when the underlying crystalline lattice structures of the surfaces are at a relative angle of 30 degrees.  However, this ultra low friction state is very unstable and upon sliding, the surfaces rotate towards a locked-in lattice alignment. Friction varies with respect to the relative angle between the two surface’s crystalline lattice structures. Minimum (ultra low) friction occurs at a relative angle of 30 degrees reaching a maximum when locked-in lattice alignment is realized upon sliding. While in a state of lattice alignment, shearing is rendered impossible with the experimental setup due to the relatively large amount of friction.

Friction varies with respect to the relative angle of the crystalline lattice structures and is, therefore, anisotropic.  For example, the fact it takes less force to split wood when an axe blade is applied parallel to its grains than when applied perpendicularly illustrates the anisotropic nature of wood, as the force to split wood is dependent upon the direction along which the force is applied.  Frictional anisotropy is greater in homogeneous junctions because the tendency to orient into a stuck, maximum friction alignment, is greater than with heterojunctions.  In fact, heterogeneous junctions experience frictional anisotropy three orders of magnitude less than homogeneous junctions. Heterogenous junctions display much less frictional anisotropy due to a lattice misalignment when the angle between the lattice vectors is at a minimum.  In other words, the graphene and hBN crystalline lattice structures are never parallel because the materials differ, therefore, never experience the impact of lattice alignment as do homogenous junctions. Hence, heterogeneous junctions do not become stuck in a high friction state that characterizes homogeneous ones, and experience ultra low friction during sliding at all relative crystalline lattice structure angles.

Presumably, to increase applicability, upscaling to much larger loads will be necessary. A large scale cost effective method to dramatically reduce friction would undoubtedly have an enormous impact on a great number of industries.  Cost efficiency is a key component to the realization of graphene’s potential impact, not only as it applies to superlubricity, but in all areas of application.  As access to large amounts of affordable graphene increases, so will experiments in fabricating devices exploiting the extraordinary characteristics which have placed graphene and graphene based materials on the front lines of material research the past couple decades.

Twenty years ago, David Boyd began his career at Caltech as a Postdoctoral Scholar with Dave Goodwin, and since 2012 has held the position of Research Scientist in the Division of Physics, Mathematics and Astronomy.  A 20 year career at Caltech is in itself a significant achievement considering Caltech’s flair for amassing the very best scientists from around the world.  Throughout Boyd’s career he has secured 7 patents, and most recently discovered a revolutionary single-step method for growing graphene.  The method allows for unprecedented continuity in graphene growth essential to significantly scaling-up production capacity.  Boyd worked with a number of great scientists at the outset of his career.  Notably, he gained a passion for science from Professor Thomas Wdowiak (Mars’ Wdowiak Ridge is named in his honor) at the University of Alabama at Birmingham as an undergraduate, and worked as David Goodwin’s (best known for developing methods for growing thin film high-purity diamonds) postdoc at Caltech.  Currently, Boyd is formulating a way to apply Goodwin’s reaction modeling code to graphene.  Considering Boyd’s accomplishments and extensive scientific knowledge, I feel fortunate to have been afforded the opportunity to work in his lab the past six summers. I have learned much from Boyd, but I still have more questions (not all scientific), so I requested an interview and he graciously accepted.

On the day of the interview, I meet Boyd at his office on campus at Caltech.  We walk a ways down a sunlit hallway and out to a balcony through two glass doors.  There’s a slight breeze in the air, a smell of nearby roses, and the temperature is perfect.  It’s a picturesque day in Pasadena.  We sit at a table and I ask my first question.

How many patents do you own?

I have seven patents.  The graphene patent was really hard to get, but we got it.  We just got it executed in China, so they are allowed to use it.  This is particularly exciting because of all the manufacturing in China.  The patent system has changed a bit, so it’s getting harder and harder.  You can come up with the idea, but if disparate components have already been patented, then you can’t get the patent for combining them in a unique way.  The invention has to provide a result that is unexpected or not obvious, and the patent for growing graphene with a one step process was just that.  The one step process refers to cleaning the copper substrate and growing graphene under the same chemistry in a continuous manner.  What used to be a two step process can be done in one.

You don’t have to anneal the substrate to 1000 degrees before growing.

Exactly.  Annealing the copper first and then growing doesn’t allow for a nice continuous process.  Removing the annealing step means the graphene is growing in an environment with significantly lower temperatures, which is important for CMOS or computer chip manufacturing.

Which patents do you hold most dear?

Usually in the research areas that are really cutting edge.  I have three patents in plasmonics, and that was a fun area 10 years ago.  It was a new area and we were doing something really exciting.  When you patent something, an application may never be realized, sometimes they get used and sometimes they don’t.  The graphene patent has already been licensed, so we’ve received quite a bit of traction.  As far as commercial success, the graphene has been much more successful than the other ones, but plasmonics were a lot of fun.  Water desalinization may be one application, and now there is a whole field of plasmonic chemistry.  A company has not yet licensed it, so it may have been too far ahead of its time for application anytime soon.

When did you realize you wanted to be a scientist?

I liked Physics in high school, and then I had a great mentor in college, Thomas Wdowiak.  Wdowiak showed me how to work in the lab.  Science is one of those things where an initial spark of interest drives you into action.  I became hooked, because of my love for science, the challenge it offers, and the simple fact I have fun with it.  I feel it’s very important to get into the lab and start learning science as early as possible in your education.

Were you identified as a gifted student?

I don’t think that’s a good marker.  I went to a private school early on, but no, I don’t think I was good at what they were looking for, no I wasn’t.  It comes down to what you want to do.  If you want to do something and you’re motivated to do it, you’ll find ways to make it happen.  If you want to code, you start coding, and that’s how you get good at it.  If you want to play music and have a passion for it, at first it may be your parents saying you have to go practice, but in the end it’s the passion that drives everything else.

Did you like high school?

I went to high school in Alabama and I had a good Physics teacher.  It was not the most academic of places, and if you were into academics the big thing there was to go to medical school.  I just hated memorizing things so I didn’t go that route.

Were AP classes offered at your high school, and if so, were you an AP student?

Yeah, I did take AP classes.  My high school only had AP English and AP Math, but it was just coming onboard at that time.  I took AP English because I liked the challenge and I love reading.

Were you involved in any extracurricular activities in school?

I earned the rank of Eagle Scout in the Boy Scouts.  I also raced bicycles in high school, and I was a several time state champion.  I finished high school (in America) and wanted to be a professional cyclist.  So, I got involved in the American Field Service (AFS), and did an extra year of high school in Italy as an exchange student where I ended up racing with some of the best cyclists in the world all through Italy.  It was a fantastic experience.

Did you have a college in mind for your undergraduate studies?  

No, I didn’t have a school in mind.  I had thought about the medical school path, so I considered taking pre-med courses at the local college, University of Alabama at Birmingham (UAB), because they have a good medical school.  Then UAB called me and said I earned an academic scholarship.  My father advised me that it would be a good idea to go there since it’s paid for.  I could take pre-med courses and then go to medical school afterwards if I wanted.  Well, I was in an honors program at the university and met an astronomer by the name Thomas Wdowiak.  I definitely learned from him how to be a scientist.  He also gave me a passion for being a scientist.  So, after working with Wdowiak for a while, I decided I didn’t want to go to medical school, I wanted to study Physics.  They just named a ridge on Mars after him, Wdowiak Ridge.  He was a very smart guy, and a great experimentalist who really grew my interest in science… he was great.

Did you do research while earning your undergraduate degree?  

Yes, Wdowiak had me in the lab working all the time.  We were doing real stuff in the lab.  I did a lot of undergraduate research in Astronomy, and the whole point was to get in the lab and work on science.  Because I worked with Wdowiak I had one or two papers published by the time I graduated.  Wdowiak taught me how to do science.   And that’s the thing, you have to want to do science, have a lab or a place to practice, and then start working.  

So, he was professor and experimentalist.

He was a very hands-on lab guy.  I was in the lab breaking things and fixing things. Astronomers are fun to work with.  He was an experimental astronomer who taught me, among other things, spectroscopy, vacuum technology, and much about the history of science.  In fact, it was Professor Wdowiak who told me about Millikan’s famous “Machine Shop in a Vacuum” experiment that inspired the graphene discovery… it all comes back to Caltech!

Name another scientist, other than Wdowiak, who has influenced you.

Richard Feynman also had a big influence on me.  I did not know him, but I love his books.

Were you focused solely on academics in college, or did you have a social life as well?

I was part of a concert committee that brought bands to the college.  We had some great bands like R.E.M. and the Red Hot Chili Peppers play, and I would work as a stagehand and a roadie for the shows.

So, you weren’t doing keg stands at fraternity parties?

No, it wasn’t like that.  I liked to go out and socialize, but no keg stands.  Though, I have had friends that were very successful that did do keg stands.

What’s your least favorite part of your job?

You’re always having to raise funds for salaries, equipment, and supplies.  It can be difficult, but once you get the funding it is a relief for the moment.  As a scientist, your focus isn’t always on just the science.

What are your responsibilities related to generating revenue for the university?

I raise funds for my projects via grants.  Part of the money goes to Caltech as overhead to pay for the facilities, lab space, and to keep the lights on.

What do you wish you could do more of in your job?

Less raising money.  I like working in the lab, which is fun.  Now that I have worked out the technique to grow graphene, I’m looking for applications.  I’m searching for the next impactful thing, and then I’ll figure out the necessary steps that need to be taken to get there.

Is there an aspect of your job that you believe would surprise people?

You have to be entrepreneurial, you have to sell your ideas to raise money for these projects.  You have to go with what’s hot in research.  There are certain things that get funded and things that don’t.

There may be some things you’re interested in, but other people aren’t, so there’s no funding.

Yeah, there may not be a need, therefore, no funding.  Right now, graphene is a big thing, because there are many applications and problems to be solved.  For example, diamonds were huge back in the ‘80’s.  But once they solved all the problems, research cooled off and industrial application took over.

Is there something else you’d really rather be researching, or are the trending ideas right now in line with your interests?

There is nothing else I’d rather be researching.  I’m in a good place right now.  We’re trying to commercialize the graphene research.  You try to do research projects that are complementary to one another.  For example, there’s a project underway, where graphene is being used for hydrogen storage in cars, that really interests me.  I do like the graphene work, it’s exciting, we’ll see where that goes.

What are the two most important personality traits essential to being a good scientist?

Creativity.  You have to think outside the box.  Perseverance.  I’m always reading and trying to understand something better.  Curiosity is, of course, a huge part of it as well. You gotta be obsessive too, I guess.  That’s more than two, sorry.

What does it take for someone to become a scientist?

You must have the desire to be a scientist, otherwise you’ll go be a stockbroker or something else.  It’s more of a passion thing, your personality.  You do have to have an aptitude for it though.  If you’re getting D’s in math, physics is probably not the place for you.  There’s an old joke, the medical student in physics class asks the professor, “Why do we have to take physics?  We’ll never use it.”  The Physics professor answers, “Physics saves lives, because it keeps idiots out of medical school.”  If you like science, but you’re not so good at math, then look at less quantitative areas of science where math is not as essential.  Computational physics and experimental physics will require you to be very good at math.  It takes a different temperament, a different set of skills.  Same curiosity, same drive and intelligence, but different temperament.

Do you ever doubt your own abilities?  Do you have insecurities about not being smart enough?

Sure, but there’s always going to be someone out there smarter.  Although, you really don’t want to ask yourself these types of questions.  If you do, you’re looking down the wrong end of the telescope.  Everyone has their doubts, but you need to listen to the feedback from the universe.  If you’re doing something for a long time and not getting results, then that’s telling you something.  Like I said, you must have a passion for what you’re doing.  If people are in doubt they should read biographies of scientists and explore their mindset to discover if science seems to be a good fit for them.  For a lot of people, it’s not the most fun job, it’s not the most social job, and certainly not the most glamorous type of job.  Some people need more social interaction, researchers are usually a little more introverted.  Again, it really depends on the person’s temperament. There are some very brilliant people in business, and it’s definitely not the case that only the brilliant people in a society go into science.  It doesn’t mean you can’t be doing amazing things just because you’re not in a scientific field.  If you like science and building things, then follow that path.  It’s also important not to force yourself to study something you don’t enjoy.

Scientists are often thought to work with giant math problems that are far above the intellectual capabilities of mere mortals.  Have you ever been in a particular situation where the lack of a solution to a math problem was impeding progress in the lab?  If so, what was the problem and did you discover the solution?

I’m attempting to model the process of graphene growth, so I’m facing this situation right now.  That’s why I have this book here.  I’m trying to adapt Professor Dave Goodwin’s Cantera reactor modeling code to model the reaction kinetics in graphene (Goodwin originally developed and wrote the modeling software called Cantera).  Dave was a big pioneer in diamond and he died almost 5 years ago here in Pasadena.  He developed a reaction modeling code for diamond, and I’m trying to apply that to graphene.  So, yeah, it’s a big math problem that I’ve been spending weeks on trying to figure out.  It’s not that I’m worried about the algebra or the coding, it’s trying to figure things out conceptually.

Do you love your job?

I do, I’ve done it for awhile, it’s fun, and I really enjoy it.  When it works, it’s great. Discovering stuff is fun and possesses a great sense of satisfaction.  But it’s not always that way, it can be very frustrating.  Like any good love affair, it has its peaks and valleys.  Sometimes you hate it, but that’s part of the relationship, it’s like… aaarrgghh!!