A Guide to Understanding Nanosensors
Nowadays, the term “nanotechnology” is thrown around a considerable amount. But what does nanotechnology really mean?
Nanotechnology simply refers to the use of technology at the nanoscale: commonly considered between 1 and 100 nanometers (nm). To put this into perspective, a sheet of paper has a width of 100,000 nanometers which is not nearly small enough to be at the nanoscale!
Within the nanotechnology field, there are many subcategories — one of which being nanosensors. To comprehend what a nanosensor is, you must first understand the purpose of a sensor. A sensor is a device that detects movement and responds by recording it and conveying it to another electronic device.
Nanosensors are essentially the result of combining nanotechnology with sensors. A nanosensor can be defined as a device that communicates information about the behaviour of particles (at the nanoscale level) to the macroscopic level — where it is visible to the naked eye.
Now that we know what nanosensors are, let's figure out how they work!
How do Nanosensors Work?
There are two major types of nanosensors: mechanical nanosensors and chemical nanosensors. Mechanical nanosensors identify movement while chemical nanosensors test for chemical concentrations. Both nanosensors work by detecting changes in the electrical conductivity of a material.
Mechanical nanosensors are made up of nanomaterials. Whenever a nanomaterial is physically manipulated, its electrical conductivity changes. This change invokes a response that can be measured using an attached capacitor because the physical change causes a quantifiable change in capacitance.
Chemical nanosensors are also made up of nanomaterials. The electrical conductivity of the nanomaterial is reduced whenever a molecule adsorbs to it. Chemical nanosensors test the electrical conductivity of the nanomaterial and measure it whenever they detect this change. Some examples of chemical nanosensors include nanowires and nanotubes.
Once the nanosensor has detected a change and measured its magnitude, the nanosensor then will transmit the information to the macroscopic level where we can make decisions based on the findings.
Why are Nanosensors Important?
Compared to the conventional sensors that are commonly used right now, nanosensors are far superior because of many reasons (to name a few):
- Nanosensors are significantly smaller making them more portable
- Because they are so small, they make less of an impact on the phenomenon being measured
- They require less power to function
- Nanosensors have greater sensitivity which allows them to be more accurate
- Nanosensors have a faster response which enables the possibility of real-time analysis
The aforementioned benefits of nanosensors bring us new kinds of possibilities at the nanoscale level (to name a few):
- Detecting airborne chemicals — chemical nanosensors enable the monitorization of chemicals in the air. This could help detect dangerous chemicals or help measure the level of pollution in the air and inform scientists of how to react accordingly.
- Measuring temperature — nanosensors allow us to measure the temperature of living cells and nanofluids. Using nanothermometers, measuring the temperature of living cells which could reveal how particles at the nanoscale level react compared to a bulk material. Nanofluids heating up in electronics has become a problem, and nanosensors can help to detect this.
- Detecting viruses — scientists have developed a nanosensor that is able to detect if someone has a virus. It works by simply having the person breathe on the nanosensor. The nanosensor will then be able to inform the person of the disease(s) that they may have. This is a breakthrough for medicine because it prevents the misdiagnosing of patients and quickly diagnoses them allowing treatment to start immediately.
Nanosensors are important because they help to bridge the gap between the nanoscopic world and the macroscopic world. We now are able to interact with and understand the particles at the nanoscale better than ever before. Nanosensors are opening doors to technological advancements in a variety of topics helping to solve some of the problems on Earth at the moment.
How are Nanosensors 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 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 slowly create a 3D image. It is the same process for building a nanosensor using the top-down method. The method commences with a bulk of material which is referred to as “bulk” in the picture above. The atoms within the material are removed one-by-one in order to eventually create a nanosensor.
Another method for building a nanosensor is the 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 the case of the bottom-up method, atoms are placed one-by-one to build a nanosensor which is illustrated by the right side of the picture above.
But why are scientists trying to improve the nanofabrication process?
Problems with Nanofabrication
One problem for both the bottom-up method and the top-down method is that they are very tedious and time-consuming making it hard for any mass production of nanosensors. Although the top-down method works well when trying to convert materials to microscale dimensions, it is much more difficult to convert materials to nanoscale dimensions. The bottom-up method is very expensive and economically inefficient due to the cost of the required equipment. Nonetheless, it is the preferred method of nanosensor production.
So how can these problems be fixed?
Potential Solutions
Presently, a new method of nanofabrication is being developed based off of the bottom-up nanofabrication method. The new method is called molecular self-assembly (MSA). It works by programming the desired structure (by understanding how each molecule will chemically interact with one another) into the shape and functional groups of the molecules. The molecules then arrange themselves into the desired nanoscale structure without any external guidance. This breakthrough offers the opportunity of mass producing nanosensors since it solves the problem of being so tedious for people to do manually. As George Whitesides, a chemist at Harvard University, put it, “Self-assembly provides a very general route to fabricating structures from components too small or too numerous to be handled robotically.”
Another potential solution for the problems of nanofabrication that would be much easier is combining parts of both the bottom-up nanofabrication method and the top-down nanofabrication method. Doing this could potentially the production of nanosensors more cost-efficient as well as a much less time-consuming process.
Thank you for taking the time to read about my findings on nanosensors. I hope you have learned something new! If you are looking to do some more of your own research on nanosensors and nanotechnology, I recommend (and also used as sources):
