Nanoscale Phenomena and Applications – A Gentle Introduction (Part 1 of 4)

One of my goals for the New Year is to write more in a non-business related capacity, going back to fond and idyllic days of pie-in-the-sky abstraction and irreverent thought before operating margins and strategic plans.  After a few tens of seconds spent searching for a good starting topic, the idea of nanoscale phenomena jumped out.  It is certainly a bigger topic than I care to delve into with any depth, but it is a nice starting point because it is at the crux of most of my current efforts – it has all the trimmings of remarkable potential, fertile innovation opportunities, challenges in commercialization, and non-intuitive barriers to entry, each deserving of its own consideration.  For now, I’ll limit the discussion to the bigger picture and provide some reflections of my learnings over the past half-decade or so, with gratuitous self-reference to my own work and those of associated research groups and present company. I'll leave the questions of how to bring about innovation in these fields as an open topic for a future musing.

You, me, and everything we generally think of as reality exist on the macroscale.  It’s the arena where our senses make sense, where we live our lives and where we can have some intuitive understanding of the world around us.  To put it a bit more technically, it’s the arena where things are continuous.  Continuity is a big point here so it is worth elaborating for a moment.  From my perspective, lounging in the lobby at O’Hare airport waiting for my flight back to Akron to board, the wall across from me is a solid object.  It’s a dull blue affair with some errant texture and a light gloss, but for all intents and purposes, I know that it is a solid slab of gypsum with a layer of low quality paint tossed on top by a team of union contractors – 3 to paint, 2 to inspect, 2 to oversee, and one to oversee the overseers, with a few trainees tossed in for experiential learning.  I know that if I took a piece and broke it in two, it would largely be the same material.  The gypsum would crumble in my hand, but one piece would largely resemble the other.  From an engineering perspective, the properties of one piece would be the same as the other, and just the same if we broke the piece down again.  Each piece would have the same hardness, the same stiffness, the same strength, the same color, and so on.  I could even toss it under a microscope and see the structure in finer detail, but everything would remain independent of size.  No matter the size of the piece, it will all be the same regardless, excepting some massive quality control issue that caused a big variation over a larger area.

The pieces that I see and interact with are on the macro-scale.  The features I see under a microscope are the micro-scale, and they might give me some idea about why the macroscale behavior is a certain way.  Perhaps there is a trace red hue that periodically pops up on the microscope due to an impurity when the paint was mixed.  That might be the reason why there is a glint in the color depending on the angle I observe the wall at.  Still, nothing too shocking or interesting.

Nanostructured materials have unique properties because of their size, which is smaller than the wavelength of visible light.  If the individual particle structure can be controlled and integrated into materials without aggregation, they offer a new toolbox for controlling material behavior in ways not previously possible.

Nanostructured materials have unique properties because of their size, which is smaller than the wavelength of visible light.  If the individual particle structure can be controlled and integrated into materials without aggregation, they offer a new toolbox for controlling material behavior in ways not previously possible.

Another way to identify the nanoscale is the point at which continuum mechanics (theories based on assumption of material continuity that describe our macro-scale quite well) begins to break down.  Continuum mechanics begins to break down once materials begin to interact with discrete physical features in their environment, which may result in electron tunneling, structural color, or unique magnetic phenomena.  Tools have been developed for modeling discrete materials, but these are unable to be extended to the continuum scale due to limiting assumptions.  Bridging relationships are needed to connect nanostructure features with bulk response - a tantalizing field of research aptly known as structure-property relationships. 

Another way to identify the nanoscale is the point at which continuum mechanics (theories based on assumption of material continuity that describe our macro-scale quite well) begins to break down.  Continuum mechanics begins to break down once materials begin to interact with discrete physical features in their environment, which may result in electron tunneling, structural color, or unique magnetic phenomena.  Tools have been developed for modeling discrete materials, but these are unable to be extended to the continuum scale due to limiting assumptions.  Bridging relationships are needed to connect nanostructure features with bulk response - a tantalizing field of research aptly known as structure-property relationships. 

The nanoscale is where things get interesting.  In a bureaucratic sense, the nanoscale is usually defined by the nanometer, which is one meter finely divided into 1 billion little pieces.  For those of us red-blooded Americans that believe in truth, freedom, and the American system of units, that’s about 25 million inches or 25,000 mils (thousandths of an inch).  If it is easy enough to find, I will toss in a nice graphic showing different things at different scales [edit: done!].  A hobbit, for example, is one of the few things that are right at the meter mark (see the attractiveness of feet – they mean something!).

The nanoscale is usually used to differentiate objects that are below 100 nanometers.  The problem is that 100 nanometers is meaningless.  There is no difference between something that is 99 nanometers and 101 nanometers, in a practical sense.  The definition that I prefer is that the nanoscale is the point at which things stop behaving like they should – where the behavior we are familiar with in the “bulk”, macro-scale starts changing.  One big problem with this definition is that the length scale of importance depends on what bulk behavior you are interested in, and sometimes also on the rate of testing (viscoelasticity is a great can of worms relevant here). The reason I like this definition is because the potential of nano-science and nano-technology becomes more clear.  If we can control the features on a size scale where things start behaving in different ways, then we can start developing new materials and new systems that can do things that conventional materials can’t.  We can have colors that never fade over time, or that change given certain stimuli, or that interact with light in a way that aren’t even visible – the famed invisibility cloak at long last.  And that is just the start, but I’ll pull back for a minute, catch my breath, and start anew with some more grounded examples.