Nanosensors: Small but mighty

7 min readMar 3, 2020

Technology has shrunk considerably over the past years. Scientists are now working on a technological breakthrough in the nanoscale.

Nanotechnology is exactly what the word sounds like, the use of technology at the nanoscale(around 10–100 nanometers). Today, this new technology is used to manipulate matter at a molecular or atomic level to produce devices with new extraordinary properties

To put this into perspective, imagine a very tall human standing on the earth, with a head that reaches the International Space Station (431 km high). The giant is reaching down with his hand (30 km across) to build “objects using materials between the size of a grain of sand [.25 mm] and an eyeball [2.5 cm].”

What are Nanosensors?

So… what are these “invisible” sensors? Before that, let’s start at the macroscopic scale. Today, portable technologies such as smartwatches carry the amazing ability to measure different bodily functions such as temperature and heart rate. They contain sensors because of how they detect and respond to some type of input from the physical environment. In these nanosensors, they are capable of different signals, including biomedical, electrical, optical, physical and mechanical signals.

But unlike regular sensors, nanosensors are microscopic. They are so small that the radius of a strand of hair is 10,000 times bigger than a nanosensor. They’re so small, that microscopes you use in your classrooms can’t see them and the nanoscale is used to measure them.

Nanoscale: the dimensional range of approximately 1 to 100 nanometers.

Why should I care about something that I can’t even see?

Regardless of your interest or disinterest in nanotechnology, it is important to realize the potential they have at changing the world. They’re almost better than regular sensors in every way, reducing the size of a sensor equates to faster response time, better signal to noise, increased data density, and having less impact on the variable being measured, which leads to more accurate data. These sensors also have the portability to be placed almost anywhere.

The possibilities for nanosensor technologies are endless, with various medical, environmental, societal, and many more opportunities at hand.

Medical:

Scientists can insert nanosensors into the bloodstream and the special properties of the nanosensor detect blood-borne biomarkers. The data that is detected would then be sent to another device wirelessly. Imagine getting a notification for when your body senses a harmful disease, so you can get treatment before you face any symptoms. Doctors and researchers can use the data obtained for cancer research and understand the health of a patient.

Environmental:

These sensors can be placed in the environment by helping to analyze environmental samples and monitor the environment’s well-being. Some nanosensors can be used for the detection of trace amounts of metals, phosphates, nitrates, and pesticides in water samples. It can also be used to trace pollutants in the air, and report that information back to scientists who then can see what the air actually has in it. Because how fast it can detect data and send the data to a monitor, it helps monitor an environment in real-time tremendously.

Societal:

Nanosensors can be placed in refrigerators to monitor food inside and notify users if an item is nearing expiration, has expired or has grown mold(no one likes rotten food). Heart rate sensors can be implemented on smart watches or phones(Textile-Based Nanosensor) to monitor and present users with information about their heart rate. They can be placed in a pool to monitor bacteria amount, chlorine concentration and other aspects that may harm the user if not treated.

How do these nanosensors work?

In a nutshell, nanosensors function like how your nervous system does. When you touch something cold, your nerves send an electric signal to your brain to register the coldness. Similarly, these nanosensors replicate that. Most nanosensors work by measuring the different electrical changes in the sensor materials it’s built to work with. For example, when a bio-substance meets the bioelectrical bioreceptor, the bioreceptor sends different signals to the transducer, which converts them into electrical signals. These signals come out as quantitative results for the computer where the data is received.

Chemical nanosensors work by measuring the change in the electrical conductivity of the nanomaterial once an analyte (a substance whose chemical constituents are being identified and measured) has been detected. Lots of nanomaterials have high electrical conductivity. This will reduce upon binding or adsorption (the process by which a solid holds molecules of a gas or liquid or solute as a thin film) of a molecule. The nanosensor detects this change and then measures it. Some examples of this type of sensor are nanotubes and nanowires.

One of the most common nanosensors is the bioelectrical biosensor, which is used to detect different analytes. It all starts when analytes and biomolecules (the molecules produced by organisms) encounter and meet the bioreceptor. The bioreceptor sends signals to the transducer, which converts them into measurable and quantifiable electrical signals. These signals are then amplified and sent to a signal processor. The signal processor processes the electrical signals and displays the results in an understandable manner.

How are they built?

Currently, to build nanosensors, there are two dominant methods: the top-down nanofabrication and the bottom-up nanofabrication.

First, let’s start with the top-down method which can be compared to an artist creating a sculpture. The artists will construct this “sculpture” of a nanosensor from the top of the structure to the bottom. The artist starts off with a block of material and a tool to carve the block with. They slowly shave off bits of the material to create a 3D image. The method commences with a bulk of nanomaterial and then the atoms within the material are removed one-by-one in order to eventually create a nanosensor. Nanolithography is one of the most commonly used forms of Top-down fabrication. It is the process of printing, writing, and etching patterns onto nanostructures. Essentially, chemicals are applied to the nanostructure and precise waves of light/electrons/x-ray/ultraviolet light damage the chemical to print patterns.

The second nanofabrication technique is called a bottom-up method. The bottom-up method can be compared to building a brick wall. In order to build a brick wall, a builder must place each brick one-by-one in its place. In this case, in the construction of a nanosensor, the bricks are the atoms that are placed one-by-one to build the nanosensor.

The problems and solutions to the nanofabrication process?

As with anything, there will always be room to grow and improve.

There are a few main issues that tend to arise when mentioning the idea of nanofabrication. This includes:

Cost (too expensive and wasteful) — Top-down: Because scientists will start with a large portion of nanomaterials(expensive) which they will take pieces of the nanomaterial little by little, this process uses a lot of energy and toxic chemicals. Not only that but there is a lot of waste, it is time-consuming, and it isn’t a process you can replicate with 100% accuracy all the time.

Time (lengthy) — Bottom-up: the time-consuming nature of placing the atoms one at a time in building the nanostructure. Furthermore, one main concern involves the fact that in order for nanomachines to self-assemble in the fashion fictionalized by science-fiction writers, many obstacles will need to be overcome such as certain principles of physics. However, this should not take away the fact that the bottom-up approach has been immensely effective, allowing techniques like the implementation of self-assembly quantum dots to surpass many of its top-down counterparts.

In short and in other words, Top-down is harder to perform, as it is etching away material with precision. On the other hand, bottom-up is harder to design and program as it utilizes self-assembly.

Both the top-down approach and the bottom-up approach have advantages. In order to enhance the nanofabrication process, however, I think that Companies and industries should start utilizing the bottom-up approach instead of the top-down lithography method more. In the future, nanotechnology is only going to get smaller and smaller. The bottom-up approach allows you to work with very small nanostructures with high precision. It also is very economical for companies because it creates little to no less nanomaterial waste. In other words, I think that creating less waste and reducing the cost is worth the extra time required when using the bottom-up approach.

In addition, I think that the manufacturing of nanosensors is quite difficult due to the fact of their sheer tininess. My idea of improving this process is to use components that bind very well to each other. This would quickly and easily put together the sensors. Another idea is to coat the sensor in a stimulant and the wires will detect how the stimulant reacts to its environment. There could be a single base nanosensor and they would be attributed specific jobs by the material coated over the sensor.