A fundamental shift in our understanding of how heat transfers from one material to another

When heat travels from one solid object to another, not all of the heat is transferred; a lot of it is reflected back at the interface. Our current understanding of how heat propagates across these interfaces is based on the thought that the more ordered the atoms of each object, the more efficient heat transfer will be across the interface. But it turns out our current understanding is dead wrong.

In a recent article published by researchers at the University of Virginia, making the interface rougher, with more defects, was shown to significantly improve the heat transfer across the interface. This was a counter-intuitive result based on the generally accepted understanding of nanoscale heat transfer, and may lead to a fundamental shift in our understanding of how heat is transferred from one object to another.

So how can this be explained? To answer that question we need a basic understanding of how heat is transferred at the atomic scale.

In a solid material, atoms are generally considered to be more or less fixed in place, being held there by bonds with their neighboring atoms. Thermal energy causes the atoms to vibrate - think ball and slinky. If we have a bunch of balls and slinkies at ordered, periodic distances, any vibration in one should be felt further away than if they were randomly oriented, interfering with each other's slinkitude (yes, I just made up that word. Patented.)

But what the researchers showed in this paper is that if you take two separate arrays of balls and slinkies (two different solid materials), and create more of a jumbled up mess at point where one would interact with the other, the vibrations coming from one would more effectively transfer their energy to the other, due to added vibrational modes.

Awesome! This means that if we can fully explain this phenomena, we can learn how to tune thermal properties from being very bad at conducting heat (which would be great for insulation, and for waste heat recovery as a couple examples) to very good at it (which would make computer manufacturers very happy)!

Postdocs

In the scientific community, there are a disproportionately large number of people who hold a PhD. The depth of knowledge needed to successfully conduct research and uncover a new understanding of how the world and universe works necessitates countless hours pouring over the published literature. Many of those who hold a PhD entered graduate school with the thought in mind that they would pursue an academic career as a professor, but the numbers simply don't work out. There are far fewer available faculty positions than there are those with a PhD. The number of PhD holders has gone up significantly, while number of faculty positions are holding steady or in decline. This leads to plenty of PhDs, but not enough jobs that equal the qualifications. Enter the postdoc. This is, by definition, a temporary position meant to augment and develop professional skills. Postdocs exist in universities, industry, and government labs. And although the goals - an educational experience meant to allow for flexibility and professional development - are the same, the manifestation of the experience can be widely different depending on the setting.
Most institutions that hire postdocs end up relying on them to reach their research goals. And in many cases, postdocs bring novel perspective, paired to the latest technology, fresh out of graduate school. And in a temporary position, postdocs often are paid less than their permanently-hired counterparts. This is a huge advantage to employers of postdocs, but can be a detriment to the postdoc, who ostensibly are in a professional development position, but are really pulling more than their full share of the weight. As a postdoc myself, I'm finding it critical to make my career desires known to my mentors and immediate supervisors, while contributing as strongly as I can to develop the capabilities that will benefit the lab. But I'm also recognizing that doing good work and keeping my head down won't be enough to launch into the career I really want. So my advice to you, if you're a postdoc or considering becoming one, is:

• Get plugged into your organization. You'll be seen as an inherently temporary member of the organization, unless you make your presence known.
• Volunteer for organizations such as Postdoc Associations, research outreach opportunities, etc. Try to find resources for people who are in a similar place in their career. That network will be invaluable to finding opportunities for longer-term gigs.
• Take every opportunity to share your research, and make sure you plug it into a broad, easily accessible context.
• Build your brand. Figure out what you stand for, what problems and skills are most important, and make your mark. 

Check out this article on Nature on the future of the postdoc for more on this topic:

https://www.nature.com/news/the-future-of-the-postdoc-1.17253

Physics and Reality - Albert Einstein on physics driving philosophy

During the early decades of the 20th century, a fundamental shift in our understanding of how the universe works, led chiefly by Albert Einstein, led to a shift in philosophy as well as science. The profundity of these discoveries are unmatched. But what did Einstein say about it? "The whole of science is nothing more than a refinement of everyday thinking. It is for this reason that the critical thinking of the physicist cannot possibly be restricted to the examination of the concepts of his own specific field. He cannot proceed without considering critically a much more difficult problem, the problem of analyzing the nature of everyday thinking." (You can read his article from 1936, "Physics and Reality" here: https://www.mitpressjournals.org/doi/pdf/10.1162/001152603771338742) Discovering the scientific explanations for everyday phenomena can lead to universal paradigm-shifting discoveries! -AW

Science in everyday life.

The frontiers of human discovery may be enabled by science, but every day, all around us, are mysteries which may be uncovered and solved by a little analysis, experimentation and deductive reasoning!

Doing science isn't restricted to fancy laboratories with equipment that costs more than your house (though, admittedly, working in one kicks butt)! A whole lot of discovery can happen in your own kitchen, with common household items, if you let your curiosity and imagination lead the way. And I can say with confidence that if you look for opportunities to think "I wonder why it works THAT way?" or "what made THAT happen?", you will come across them every. single. day.

So that's my challenge! Find these areas of daily intellectual curiosity. It could be something like "why does my laptop get hot when it's running?" or "why do I get a shock sometimes when I touch a door knob?" Email questions like that to me, or comment them here. I will read them and will periodically come up with a strategy to test them, including all materials needed to try it for yourself. This section of the blog is up to you! It's your creation. 

Happy exploring!
-AW

 Gif credit: http://kidshealth.org/EN/images/headers/K-electricShock-enHD-AR1.gif

Still plenty of room at the bottom?

Following up on Plenty of Room at the Bottom - how did Feynman do?

As I pointed out in an earlier post, Feynman's quintessential article imagines what accomplishments of which very, very tiny technologies and machines might be capable.

To summarize the contents of the article, Feynman:

• Appeals to visual logic by calculating how little space printed materials really need to take up (he shows that one could write the entire contents of all the volumes of the Encyclopedia Britanica on the head of a pin)
• Imagines a way, based on technologies available in 1960, to write and copy "written" information at such a small scale
• Describes how, by taking advantage of all three spatial dimensions, all print copies of every written medium in 1960 could fit on a spec of dust.
• Points out a need for the development of a better electron microscope to take this information processing strategy from being a possibility to becoming a reality; he also talks about several earth-shattering consequences of an electron microscope able to map and manipulate individual atoms
• Discusses possibilities and advantages of miniaturizing the computer
• Imagines miniaturizing machines, such as cars and robotic hands, and thinks through the logistical limits of scale, such as the volume needed in the engine blocks for combustion to occur, or the limits of human dexterity.
• Calls for high-school contests which use such "miniaturization technology"

So how did Feynman do? Nearly 50 years later, what has become reality and what is still a beckoning call to the modern physicist? 

• Computers are VERY much miniaturized compared with what they were in 1959. The logic gates used in modern computers are, in fact, reaching the limits of size, going down to about the scale Feynman calls out as the size limit (100s of atoms). New strategies are emerging which will allow for further increases in computational power once the limits of conventional electronics are reached (more on that in an upcoming blog post)! 
• Information is stored in very tiny capsules. Just think, the computer or smart phone you're using to read this has the ability to store about as much information as five average sized libraries! All in the palm of your hand.
• Modern electron microscopes have aided in the understanding of biological processes, and was instrumental in DNA sequencing, essential in mapping the human genome
• There are communities supporting high school students who regularly use scanning electron microscopes to take images such as this (a moth's eye):

photo credit: http://remf.dartmouth.edu/images/insectPart3SEM/image/22noctuidae120.jpg

For all the remarkable predictions Feynman made, some of his dreams have yet to become reality. These include: 

• a high numeric aperture electron microscope, capable of repeatably and reliably manipulating individual atoms
• miniature robotic hands capable of manipulating at the nanoscale (although there are tools which can be used to physically scribe things at that scale, such as the atomic force microscope)

One of the most important aspects of the continued development of the field of nanotechnology is understanding how physics is different at that scale, and what effects that are imperceptible to us at the scales we deal with in our day-to-day lives affect the nanoscale miniatures we're making every day. Several of the upcoming blog posts will deal with some of these weird effects and how we can explain them. 

Detecting Gravity (2017 Nobel Prize Winning Research)

Gravity. The stuff that keeps you grounded. And the stuff (from extremely distant stars and galaxies) that ripples all of earth's atoms a tiny, tiny amount all the time. Can we detect those ripples?

For eons, we've speculated (at best) as to what gravity is, and where its physical basis comes from. Albert Einstein, who pioneered the theory of general relativity which described gravity as a fundamental consequence of mass, and can lead to the strange distortions in space and time, thought it would be impossible to directly measure gravitational waves on earth, unless there was a nearby cataclysmic event (such as a neighboring galaxy getting sucked in a black hole). Until just a couple years ago (2015), it was impossible to measure gravitational waves. That is, until over 1000 researchers from more than 86 institutions came together and established the Light Interferometer Gravitational-wave Observatory (or LIGO, for short). There, they experimentally detected gravitational waves for the first time. 

The team used lasers that they beamed into two different perpendicular directions, one went north and the other one west. The mirrors were carefully positioned so that they were EXACTLY the same distance from the source. The effect of the gravitational waves that were reaching earth caused the mirrors to expand in one direction, and contract in the other. This effect was so weak that the net change in location was less than 1/1000th of an atom! But the LIGO team had carefully, painstakingly, accounted for every possible source of experimental noise which would drown out such a vanishingly small signal. And in the end, they found it. Two identical experiments at different parts of the country observe consistent results and now we have a way to directly observe how gravity warps spacetime.

 

photo credit: https://www.ligo.caltech.edu/assets/ligo_default_social_image-fa8a65b147c61b5147e1d43f9e7afc98.jpg

 

Bending the laws of thermodynamics at the atomic scale

Laws of Thermodynamics? More like suggestions!

This news feature, posted on Nature's website recently, discusses how various forms energy (heat, electricity, magnetism and light particularly) behave differently at the atomic scale. The laws of thermodynamics might not be breakable, but they can be bent! The following quote from the news feature demonstrates an example of how the standard laws of thermodynamics may, under special conditions, break down at the atomic scale.

Experiments are starting to pin down that quantum–classical boundary. Last year, for example, Schaetz and his colleagues showed that, under certain conditions, strings of five or fewer magnesium ions in a crystal do not reach and remain in thermal equilibrium with their surroundings like larger systems do.

In their test, each ion started in a high-energy state and its spin oscillated between two states corresponding to the direction of its magnetism — 'up' and 'down'. Standard thermodynamics predicts that such spin oscillations should die down as the ions cool by interacting with the other atoms in the crystal around them, just as hot coffee cools when its molecules collide with molecules in the colder surrounding air.

Such collisions transfer energy from the coffee molecules to the air molecules. A similar cooling mechanism is at play in the crystal, where quantized vibrations in the lattice called phonons carry heat away from the oscillating spins. Schaetz and his colleagues found that their small ion systems did stop oscillating, suggesting that they had cooled. But after a few milliseconds, the ions began oscillating vigorously again. This resurgence has a quantum origin, says Schaetz. Rather than dissipating away entirely, the phonons rebounded at the edges of the crystal and returned, in phase, to their source ions, reinstating the original spin oscillations.

- Z. Merali

So what impact does this have on technological developments? It demonstrates some of the ways in which as we try to miniaturize computer components further and further, the systems tend to no longer behave as expected. Instead of the thermal energy dissipating and staying away (as your coffee would eventually reach room temperature), these effects mean that the heat may be trapped, and eventually cause burn-out of the electronic components. However, the effect may also be used to process quantum information at higher temperatures - a major present hurdle to the realization of practical quantum computers.

Having been a theoretical discussion piece for the better part of 30 years, quantum effects on the laws of thermodynamics have lacked from experimental results, demonstrating such effects. The news feature discussed here showcases some recent experimental results which do just that.  

Photo credit: https://www.nature.com/news/the-new-thermodynamics-how-quantum-physics-is-bending-the-rules-1.22937

Plenty of Room at the Bottom

Plenty of Room at the Bottom

Nobel prize winning physicist, Richard Feynman, wrote an article in 1959. The title of the article was "There is Plenty of Room at the Bottom.": a call to action to physicists of the day to embrace an experimental exploration of the physics of the very tiny. He imagined what advancements, achieved through nanotechnology, might be like in the year 2000. His description is very inspiring, and presents the case very well how nanoscience is an area with plenty of room to explore. The effects go far beyond what he describes, and the technological reaches seen today are astounding. I will follow up with specifics and compare what Feynman predicted with what has been achieved since this was penned back in '59. Enjoy reading! 

-AW

Photo credit: http://www.nanobusiness.org/images/nanobusiness-nanotechnology-as-science-feynman.jpg

Welcome to the Human Frontier!

Scientists: the modern-day explorers

Few things pique my curiosity more than the limit of human interaction with the universe. It stirs the same part of my soul as learning of the voyages of Marco Polo, Amerigo Vespucci, Magellan, Columbus, Lewis and Clark... Western explorers of uncharted reaches of the earth. 

Today, there are few places on the surface of earth which are uncharted, but above us and below us, and the realms around us which cannot be seen by unaided eyes remain a mystery. 

The explorers of bygone centuries planned their voyages, trained for years, assembled highly skilled teams of brave souls willing to leave the world they knew behind for good, not knowing what they were going to encounter. They brought along the best technology of the era to explore these mysterious lands. The first explorers recorded everything to the best of their ability, but inevitably, there were some mistakes and misinterpretations along the way. Later explorers corrected and refined these explorations until we had an accurate understanding of the "New World". This is the same as the scientific endeavors of today. We, the scientists, are the modern-day explorers. We, the engineers, are on the human frontier. We will go bravely wherever the data takes us, and we will boldly proclaim, to the best of our ability, an accurate and precise interpretation of the data, expecting and eagerly anticipating corrections to reports and deviations from our apparent course.

This blog is a space where I will periodically share inspirational advancements in humanity, in our understanding of the universe. Check back for new and interesting discoveries! 

Photo credit: http://eskify.com/wp-content/uploads/2016/08/explorers-of-the-new-world_00003-1080x675.jpg