Nanotechnology & Nanosensors

Measuring less than one ten thousandth of a millimetre and working in real time, nanosensors are technological trailblazers due to their radical and groundbreaking abilities.

In 2014, Fernando Patolsky developed a sensor that could detect the scent of molecular explosives better than a detection dog — and if that was six years ago, just imagine the possibilities now!

To read more about this breakthrough, click here.

Now, let’s take a closer look at nanosensors…

What exactly is a nanosensor?

A nanosensor can be simply defined as a minuscule version of a sensor, which detects and measures specific properties and bears data to be analyzed. There are two unique characteristics of a nanosensor: at least one of its dimensions measure between 10 and 100 nanometers, and they can detect particles on the nano-scale.

The nano-scale

“What is the nano-scale?” you may ask. Well, the term basically denotes something of a size measurable in nanometers or microns. To give you an idea of how utterly tiny a nanometer is, try to wrap your head around this; a single sheet of paper is 100,000 nanometres thick. Insane, right?!

The importance of nanosensors

There are several reasons that nanosensors are of great significance and influence, especially in the modern day. Essentially, they are the future in technological advancement, offering extremely beneficial modifications to various industries such as medical, military and environmental. They also open up many opportunities to further develop similar technology in the future, benefitting mankind. Here’s a rundown of why these tiny sensors are capable of making such a huge impact.

Nanosensors are:

• Accurate
• Portable
• Light-weight
• Power-saving
• Fast
• Efficient, as they are portable and can work in real time
• Capable of detecting inorganic, organic or biological materials
• Able to recognize and respond to particular molecules

They are important to the medical industry because :

• They allow doctors to quickly detect illness and disease by simply sampling blood or saliva
• They offer sensitive diagnosis and precise detection at an early stage
• They are less invasive than conventional methods and thus result in lower risk
• They allow for easy, safe, and quick on-site testing, even if there’s no lab

They are important to the military because they can :

• Detect explosives
• Distinguish gases
• Recognize existing toxic gases
• Alert the user when they are in danger
• Monitor soldiers’ health and vitals

Moreover, the military can benefit from nanosensors the same way that the medical industry can, as they too require some of the same needs.

They are important to the environment and us because :

• They can detect pollutants in the air, therefore paving the way for air quality improvement
• They can detect bacterial contamination during the packaging, distribution or storage of food
• They can detect chemicals, microbes and bacteria in water to monitor water quality
• They have the ability to work in real-time, a treasured property of environmental monitoring applications

“Nanomaterials are also easily customizable; their size, structure, and composition all influence their properties, and together, these variables produce a nearly endless array of combinations.” - Laurel Hamers, Centre for Sustainable Nanotechnology

Hence, nanosensors are not only going to accelerate the development of technology use in a wide range of professions, but also lead the way for a boundless scope of new opportunities (on the nano-scale of course) in the coming generation.

How nanosensors work according to their class

To put it simply, nanosensors detect changes in their environment and interact with their nano-components to create electrical signals from the observed material in order for them to be analyzed.

However, more specifically, although there are many different sorts of nanosensors, there are two classes of nanosensors, each with unique sensing mechanisms. They’re called chemical nanosensors and mechanical nanosensors.

Chemical nanosensors measure the change in the electrical conductivity of the nanomaterial, once the chemicals of the substance that’s being tested have been detected. There are two components : the receptor and the physiochemical transducer. They work together to deduce the type or the concentration of a chemical substance.

THE PROCESS :

1. The receptor checks the composition of the chemical reaction in the sampled material or process and speeds it up (acting as a catalyst)
2. The receptors interacts with the transducer, which gathers its information and sends an electrical signal to the signal amplifier
3. The signal is amplified from the transducer and an output signal is sent
4. The signal is finally analyzed detected

Similarly, mechanical sensors tend to measure electrical changes as well.

Mechanical nanosensors are sensitive to changes in mechanical properties, what is to say physical properties that a material exhibits upon the application of forces (although not in all cases). They play an important role in molecular detection and other biomedical applications. A few examples of where a mechanical nanosensor would be used are to measure variables such as pressure, volume levels, velocity, temperature, acceleration, position, force, pressure or flow.

Next, let’s take a look at how nanosensors and other nano-structures are built, also known as the process of nanofabrication.

Nanofabrication

Producing such an intricate, high-technology device like a nanosensor is no less complex as it would seem. For that reason, there are numerous existing methods in nano-fabrication. However, they do fall under two main groups of methods : top-down and bottom-up nano-manufacturing.

The two methods of nanofabrication

Top-down nanofabrication basically involves a process of taking a large chunk of material and removing the unneeded parts of the material until you end up with the desired size and shape. Common top-down methods include different sorts of lithography, such as nanoimprint, optical and electron beam lithography, although the most conventional technique is photolithography. Photolithography is where you transfer previously made shapes from a template onto a surface using lights. There is also nanolithography, where the necessary part of the nano-material is shielded by a mask and the rest is etched away.

The process of nanolithography.

Bottom-up fabrication on the other hand works differently. Chemical and physical forces are used in order to put together simple units into a bigger structure, imitating biological processes in nature. This is where singular atoms pile onto each other, finally forming molecules. As you can tell, there are a variety of ways to go about doing anything involving nanofabrication!

Problems with nanofabrication

With nanotechnology, one of the main problems remains the cost. The same thing goes with nanosensors and consequently nanofabrication. But other than the general expense of the whole process, each method of nanofabrication also holds their own disadvantages and challenges.

Disadvantages of top-down nanofabrication

Firstly, top-down nanofabrication methods produce quite a lot of waste and often require a fair amount of energy. To add to that, the chemicals that are used during the process can sometimes be extremely toxic. Among other problems, the structures that turn out from a lot of top-down methods are usually unique and therefore not easy to replicate. So, if there were a need to create multiple copies of a device for a certain use, this would likely cause a problem. On top of that, top-down methods can be time-consuming and resource-intensive.

…and bottom-up nanofabrication

Similarly, bottom-up approaches are time-consuming — although they have been proven to cause less defects in the nanostructure compared to other top-down methods. The problem with bottom-up nanofabrication is that some aspects of the method are still not fully understood and therefore cause its reliability to be questioned.

How I think the nanofabrication process could be improved

The integration of solar-power

Nanosensors are known to use less energy than other conventional devices that would be used in their place, but that’s not to say that they don’t use any energy. For that reason, I think it would be brilliant if processes in nanofabrication could make use of solar energy! As it turns out, solar powered sensors actually do exist. In fact, a company named Unitronic has released a wireless, solar-powered sensor called the Unitronic Solar CO SensorSo (as mentioned on eeNews), which monitors the concentration of carbon monoxide. As the use of solar power has already been proven to function in sensors, this can be applied to nanosensors because their size is one of the only characteristics that sets them apart from regular sensors. This would not only be great for the environment, but overtime, they would be able to pay for themselves. This means that even the issue of cost would be addressed!

Giving nanosensors the ability to identify normal bodily functions

Another thing that I think could be improved is the sensor itself and its capabilities. When certain sensors are used for medical purposes, they can detect things in the body and classify them as a threat to the patient when they’re really within a normal range for the patient’s pre-existing condition. The reason for this is their ability to execute early detection. For instance, a nanosensor could detect micro tremors in the body that would have been dealt with on its own, but instead cause reason to believe that they require unnecessary, harsh treatment. That’s why I think that nanosensors should be able to identify normal bodily functions so that it doesn’t detect everything that it finds. Given that the human body and its functions are so diverse, there should be technology that helps deem these sorts of bodily functions normal. This would help make sure that only the most worrisome abnormalities would be detecting rather than providing excessive information or “false alarms” which could frighten patients.

Overall, I think nanosensors have the ability to offer some truly innovative solutions to the diverse problems in our world. Although there are barriers that may cause limits to their potential, like any problem, I believe that these barriers will eventually be overcome with new technology and futuristic ideas. I hope that you have enjoyed learning about this topic as much as I did, and I urge you to continue to dive deeper into the world of not only nanosensors but nanotechnology as a whole.