The Nanoscience behind Breath Analysis

Let me begin by asking every reader a simple question, What would happen if we were to drop a pen on the ground? The obvious answer would be that it would fall due to the force of gravity doing its work. Now, tell me what would happen if we were to drop a nanoparticle? Will gravity have the same effect?

In order to answer this question, we need to first know what a nanoparticle is. NANO means one billionth. A nanometer is one billionth of a meter. A baseball bat is one meter, my fingertip is one centimeter, the eye of a needle is 1 millimeter and a single strand of human hair is a hundred micrometer, which might be the smallest division that we can see with our naked eyes! Now take that and keep dividing the number by 10 to get the size of a blood cell, the diameter of a bacteria, and the size of a virus respectively. Dividing this yet again by 100 we get 1 nanometer which is the size of half a DNA. One nanometer is only 5 atoms sitting end to end.

Now that we know the size of a nanometer, it’s time the address the following: What is so special about a nanometer? Why are we so obsessed with making things smaller and smaller in size?

Of course, we understand that smaller - is lighter, is cheaper, is faster, and is smarter. Take a computer and a smartphone for example.

Nanotechnology is not necessarily about making things smaller for the sake of it. It is because science has different rules in the nanoscale. The physical and chemical properties of materials change dramatically at this level. The best example is a gold ring. It looks golden in color but the gold nanoparticle is not necessarily golden. It can be red, purple, blue, or even green. This is known as the quantum effect; materials when reduced to the nanoscale can suddenly show different properties than what they display on the macroscale.

Let us revisit the pen and gravity activity. In our everyday life, gravity is the most important force we encounter. It dominates everything around us. But on the nanoscale, gravity is absolutely nothing. It is negligible and much less important than other forces like the electromagnetic forces (between the atoms and molecules) or the thermal vibration of atoms in a nanostructure. If we drop a nanoparticle, the dynamics of such a small object would be much more sensitive to the factors like Brownian Motion or Turbulent Diffusion than gravity.

In short, the game of science has different rules when you play it in the nanoscale. But if we know these rules, and if we know how to play this game, we can design new materials, manipulate their properties and train them to make them behave the way we want them to do. Nanotechnology can also bring about major changes in the field of medicine. One way of this is by designing not only small but intelligent nanosensors in the laboratories, that can be trained to sniff out our breath. We might not know this but our breath actually tells a story and this story can be used to save our life. We smell different when we are sick, and our nose is not strong enough to detect it. The body chemistry changes when we are sick and as a result of that chemistry change, some ball markers are released into our breath. This gives us the unique opportunity of detecting disease just by sniffing one’s breath.

But there is one big challenge here. These ball markers in our breath exist at a very low concentration; in the order of ppm (parts per million) or ppb (parts per billion). I’ll give an example to help you all visualize a ppm better. The entire Harry Potter series (7 books) has 1 million eighty-four thousand one hundred seventy words. This makes the word Dumbledore on page 17 of Harry Potter and the Philosopher’s stone a little bit less than 1 ppm. One ppm might look small, but it is still very impactful! This can be understood by looking at Acetone. Acetone is a well-known ball marker for diabetes. If one in a million particles in our breath is acetone, we are healthy but if two in a million particles in our breath is of acetone, it is an indicator that one may have diabetes. Therefore, the difference between a healthy person and a sick person lies in one part per million of a compound.

So, in order to detect disease using human breath rather than blood, we need to fabricate and design super-sensitive sensors which can detect ppm or even less (ppb) concentrations. Before nanotechnology came into play, it was impossible to precisely detect such a tiny concentration but today we have sensors that are hundreds of times more accurate than what we need. Using these, we can detect two parts in every billionth particle in our breath. But how does nanotechnology help in the fabrication of such a small sophisticated sensor? It is actually all related to the available surface area. Any Material at the macroscale when shrunk to the nanoscale has a surface area 10 million times larger, while still having the same mass and same volume. Similarly, by shrinking the structural elements of the sensors down to the nano level, we can significantly increase the surface area available which in turn helps to capture that tiny concentration of the ball marker in our breath.

Nanoscience is not just one science – it is a cumulation of different sciences that includes biology, chemistry, physics, electronics, medicine, material science, and engineering. It has time and again shown its potential to positively impact our quality of life.

Breath analysis is one of the many research areas in this field that can empower us with better diagnostic technology and can help us save many lives in the near future.

- Trisha Daftari