What are nanosensors?
Nanosensors are an umbrella term for any device that is capable of conveying information about a particle at the nanoscale(one-billionth of a meter). Nanosensors measure physical aspects and converts them to signals that can be recorded and analyzed.
But first off how big — or in the case small is a billionth of a meter? Take a look around you, what is the smallest thing you see? If you can’t find anything look at a piece of paper. See how thin it is? Now try to imagine it 75,000 times smaller. That’s about how big a nanometer is. Another way to visualize a billionth of a meter is to look at the width of a dime compared to the diameter of Earth. Pretty small, isn’t it?
So… how are they built?
After realizing how small a nanometer is, you probably have one question, how can you build at that level? How can you manipulate a structure so small that light itself cannot reach it? Is there even a method to create at the nanoscale? The answer is surprising because there are actually several ways to interact in the nanoscale the most notable being top-down lithography, film deposition and etching.
Top-down lithography
Top-down lithography is similar to sculpting. You start off with a marble block, or in the case material of your choosing; you then proceed to eliminate the components you do not need. You continue to eliminate until you achieve your desired nanostructure. One of the most common form of top-down lithography is photolithography. This normally involves an oxidized silicon wafer which is than coated with a photoresist layer. Light is transferred with a geometric pattern onto the to photoresist, which undergoes a chemical reaction when exposed to these ultraviolet rays. It results in the layer dissappearing. The photoresist is than stripped away.
Film deposition
Have you ever seen a 3D printer? The printer starts off with a base and slowly works up depositing plastic layer by layer. Film deposition is essentially the same exact thing, you build upwards depositing atoms or molecules one at a time on a substrate to create a nanostructure.
Etching
There are two distinct types of etching, chemical wet etching, and dry etching.
- Chemical wet etching occurs is performed in a chemical fume hood lab using solvents, mixtures, acids etc.
- Dry etching utilizes reactive gases instead of liquids, these include reactive ion etching and inductively coupled plasma etching.
Problems with Nanofabrication
Nanofabrication is similar to threading a needle, it requires utmost concentration and a suitable environment to put it lightly. Contamination is a key issue, after all when the very air can result in defects a perfect environment is hard to simulate. Speaking generally as well, cost, efficiency, quality, and complexity are common issues too. Developing nanostructures costs a large amount, due to equipment, manpower, and efficiency. Nanofabrication and nanotechnology are relatively new subject areas, there are few qualified individuals or individuals at all in these respected fields. This results in lower overall quality as well as higher labor costs
Why are nanosensors important, what does it even do?
Even though the cost and development of nanosensors are so high, the ROI is definitely worth it. Nanosensors are important due to their contribution to nanotechnology, and nanostructures. Building nanostructures without nanosensors is similar to painting while your eyes are closed. Very hard to do a good job with. Nanosensors ability of detecting accurately and in realtime also has many application.
Currently, the largest application for nanotechnology is in healthcare, nanosensors are able to do a variety of things such as identifying tumors and monitoring organ health.
Identifying tumors
“One example of nanosensors involves using the fluorescence properties of cadmium selenide quantum dots as sensors to uncover tumors within the body.” In plain English researchers have developed a way to discover tumors within the body, utilizing quantum dots (a type of nanosensor). These dots bond to their targets (the tumor) and the dots fluorescence properties causes it to light up, which makes identifying the tumor simpler.
Monitoring organ health
Silicon nanowires (a type of nanosensor), is placed in IV lines in order to monitor organ health. These nanowires detect biomarkers (an indication of disease, infection, etc). This allows for constant observation of any biomarkers in real time.
Nanosensors can also detect issues in organ implants, the nanosensor is attached to the implants and is able to detect if the cells are healthy or not.
Nanosensors have a variety of application in areas such as military, and food too. They help detect dangerous gases and other substances. Companies such as Biofingers have developed a device using nanocantilever, to detect, harmful pathogens, microbes and undesired substances in food products. As well as Navy Research Laboratory Institute for Nanoscience, who are developing protective gear that uses quantum dots to identify dangerous gases. These applications are fascinating and important, and are definitely worth getting into.
But how do nanosensors work?
There are two main types of nanosensor chemical and mechanical nanosensors.
Chemical nanosensors, detect chemicals (surprise!), they work by measuring the change in electrical conductivity of the nanomaterial of an unknown substance. Examples of chemical nanosensors are nanowires and nanotubes, they convert variations into a physical quantity and then send a message once the substance has been identified. A good example is the silicon nanowires used to monitor organ health, which distinguishes between different substances.
Mechanical nanosensors are a bit different from chemical nanosensors. Although mechanical nanosensors use electrical conductivity to, the process still heavily differentiates from chemical nanosensors. The mechanical nanosensors change its electrical conductivity when the material is manipulated, this change then triggers a recorded response.
How can I improve nanofabrication?
Cleanliness is close to Godliness
When working with nanostructures another things scientists can do is to use a vacuum. Vacuums minimize oxygen atoms that may contaminate the nanostructures. Which results in fewer defects, and more efficient development.
Recent advances in technology such as Artificial Intelligence can also help improve nanofabrication. Strong AI can help streamline the process, generate new ideas, and introduce a different perspective.
There should also be better sources of information for nanofabrication. When researching on nanofabrication, many websites were poorly written and designed. This makes the information on some level inaccessible and severely stunts the growth of further innovation.
Although these are small steps, like this article has (hopefully) proven to you small things make a big difference.
In conclusion, I encourage you to think big. To think about all the things nanosensors can be used in, the innovations, technologies and billions of people and impact. But also to think small, as small as a billionth of a meter.
