Nanosensors: The Future of Technology

When you typically hear about nanotechnology, you might think of tiny robots that can do just about anything. Perhaps that idea is not too far off from reality…

7 min readMar 31, 2019

Nanotechnology is being proposed as a solution for many of the world’s most complex problems, such as making high efficiency solar cells, creating a cure for cancer, and even decontaminating our water sources. These are all incredible claims, but to understand what makes nanotechnology so brilliant, we must know what nanotechnology really is.

By definition, nanotechnology is the design, production, and application of devices, structures, and systems at the nanoscale. This definition may seem confusing, as it is hard to understand how small nanotechnology really is. One nanometer (nm) is defined as one-billionth of a meter. In fact, a nanometer is so small, it would only take a line of 10 hydrogen atoms to be as long as seven nanometers.

The image showcases the true scale of a nanometer. Taken from: The Australian Academy of Science.

When did we first start using nanotechnology?

At this point, you may be thinking, “How can we work, let alone make technologies at such a small size?” Well, it may surprise you that humans had used nanoparticles in the 4th century CE, with glass. The Romans managed to create gold and silver particles to be as little as 50 nm wide, and infused them into the glass. When the cup had light absorbed by larger gold particles, it would turn red, and it would turn green when light was absorbed by the smaller silver particles.

Both colour variations of the Lycurgus Cup, shown in both the red and green variants. Taken from: The British Museum

Now that our scientific and technological capabilities have far exceeded those of the Romans back in the 4th century, we can use nanotechnologies to create new innovations in all fields. One modern application of nanotechnology is through the use of nanosensors.

Nanosensors, an overview:

What exactly is a nanosensor? Think of a normal sensor, a device that can respond to a property. In your everyday life, it could be the IR sensor in a TV remote, a blood pressure or heart rate monitor, or maybe even a smoke detector. All of these respond to stimuli and return a specific result, but they are nowhere near being on the nanoscale.

Now imagine the smoke detector, but only 15 nm wide. It can detect the concentrations of various gases, with multiple times the accuracy of the typical smoke detector. When combined with millions of other similar sensors, it can be placed onto wearable technology and monitor clean air around you. This is an example of what a nanosensor is like, simply a sensor at the nanoscale.

The image above is a diagram of a nanosensor responding to low concentrations of ammonia and water. Taken from: Royal Society of Chemistry

Nanosensors may be new and cool, but why are they so important?

The importance of nanosensors can not be understated, as by using them, we can monitor bacteria in a patient, keep track of nitrous oxide emissions in vehicles, detect instabilities within nuclear reactors, and even keep solar cells clean. By giving us access to all this data, and performing these important tasks, nanosensors are essential towards improving human quality of life, the Earth’s condition, and furthering technology as a whole.

Composition:

Nanosensors are made up of various nanomaterials, with the most important factor in a material’s effectiveness being electrical conductivity. The most common nanomaterials by far, are all variants, or allotropes — a different physical form of an element — of carbon. The materials most often discussed are graphene and carbon nanotubes. When in these forms, carbon is very conductive to electricity, and makes for a great nanomaterial. Titanium dioxide and silicon are other substances that have also shown effectiveness.

Carbon nanotubes and graphene are made up of a hexagonal lattice formation of carbon atoms. These are incredibly strong and electrically conductive. Taken from: Science Daily

There are two main types of nanosensors, chemical and mechanical…

As the name suggests, chemical nanosensors are used to detect and analyze chemicals and their properties. They work by making use of changes in the analyzed substance’s electrical conductivity. Nanomaterials such as carbon nanotubes respond to these changes, and reduce their conductivity based on the substance. These materials specifically, are very efficient sensors, as they can both convert changes into an electrical current and act as the wire to transmit the current at the same time. Mechanical nanosensors in comparison, change their conductivity as a response to when the nanomaterial is interacted with, something that we can detect. These can be recorded through capacitors.

Nanofabrication:

As humans it is hard for us to imagine us working at a level so small that we can not even see it with our own eyes. However, that does not mean scientists have not found ways to create nanomaterials and nanosensors, or using the official term, nanofabrication. There must be over a dozen of ways to produce such materials, so I will be going over the three main methods of production.

The first method is called atomic layer deposition, where a thin film is slowly deposited onto an underlying substance, or substrate, which acts as a platform. The film is deposited atom by atom, within something known as a reaction chamber.

The image above showcases the atomic layer deposition cycle, of depositing the various materials on the substrate. Taken from: ctech Nano Coating Technologies

The second method is nanolithography, which is essentially printing out or sculpting away at the particles until the desired result is achieved. Using optical lithography, different wavelengths are used to change the solubility of specific particles, so they can be “washed away” in a liquid solution. Additionally, using electron-beam lithography, we can remove materials with an accuracy of under 10 nm with a similar method.

The third method is known as self-assembly, and is easily the most futuristic. A good comparison would be how Iron Man’s suit can move and assemble itself upon request. Self-assembly uses the chemical and electrical properties of a substance to arrange them into the wanted material or form. This technology is still primitive, however it seems to have the greatest potential.

A chemical solution can be used for self-assembly, arranging the nanomaterials in the desired form using its chemical properties.

If nanotechnology is so brilliant, why do we not see it more often?

A primary reason for us not using nanotechnology in our everyday lives is the fact that nanofabrication has many problems that make it difficult to create nanomaterials.

The materials used in nanofabrication need to be extremely pure, and sourcing and isolating pure elements can be extremely expensive.
The equipment for a small scale atomic layer deposition or nanolithography setup may cost between $600,000 to a few million USD.
The process of fabrication takes a very long time, with only about 200–300 nm of film being deposited per hour using atomic layer deposition. Lithography is slow in a similar manner, not yet fit for mass production.

An image of the nanofabrication process within a laboratory. Taken from: King Abdullah University of Science and Technology

Are there any ways to solve these issues?

Over the course of learning more about nanofabrication as a whole, I have been trying to think of solutions to the issues we currently face when it comes to the processes. As I am not an expert on the subject, I can not vouch for the viability of my ideas, and only provide them.

I will be tackling each of the problems I have listed above, and attempt to think of a reasonable solution for them.

In regards to the sourcing of pure elements, this will always be a difficult process, as even if scientists attempt to purify the element with a chemical solution, residue will remain. My idea is a potential solution to the residue problem, described as the following: The specific molecules and can be heated through a beam which would then be removed through an electromagnet. This has been tested in relation to other technologies, but it may also work for nanotechnology.
Cost of production will go down as the technology develops and becomes more prevalent. Once nanotechnology becomes more mainstream, perhaps governments can further support laboratories in equipment expenditures as well.
When it comes to the time taken by nanofabrication, the best solution may be to develop upon or try new methods of it. One such method which may be plausible is creating moulds for specific nanosensors or nanomaterials, and attempt to “spray the nanoparticles” onto them. Similar methods are already being used, except they involve using stencils and cutting out the right pieces. Though my proposed solution would be much faster, it may lead to the wastage of material, which should be an important consideration.

A nanoscopic electromagnet made of graphene may be capable of pulling away residue particles in the nanofabrication process. Taken from: Graphene-Info

Takeaways and Good Sources:

In the past few decades, the way we treat nanotechnology has turned from a far off fantasy into a potential reality in the near future. Although our research and development will still take many more years to refine, our current progress has been outstanding, and is working to solve some of the world’s largest problems, despite their nanoscopic size.

When it came to all this research and information, I found many good sources that provide deep and useful insight that explain the ins and outs of all things related to nanotechnology. Here they are: