With the constantly developing world, new technologies need to be developed to keep up. In this article, we will begin to explore the notion of one of the most versatile developments in technology. Nanosensors. Nanosensors are nanoscale devices that are used to measure physical quantities and convert those into signals that can be analyzed. Nanosensors are usually used to perform nanoscale measurements though they are not necessarily nano in size. To be considered a nanosensor, the nanodevice must either have dimensions within 10 to 100 nanometers or the distance between the analyte* and the sensor must be within the nanoscale.
The objective of these sensors is to screen and measure any chemical, mechanical, and physical changes that are related to the analyte. Nanosensors have various functions in various fields of study though they are commonly used in the medical and biomedical areas.
The importance of nanosensors varies with the task at hand. From a medical standpoint, these devices have, in a way, revolutionized modern medicine, their ability to detect and quantify data at molecular data has allowed practitioners to enhance their diagnosis or catch something early on. May it be by monitoring metabolites within body fluid to catch disease-related metabolites early on or finding the pathology of tumours within the body, nanosensors play an essential role within medicine. Furthermore, these devices can then be assimilated into other systems (e.g., labs-on-a-chip) to simplify the desired detection, and act as miniature biomedical or chemistry laboratories built on a small glass or plastic chip. Moving away from the medical standpoint, nanosensors are also implemented in defence-based applications such as detection for explosives or toxic gas.
What Makes Them So Great?
- These devices allow us to observe the world on a nanoscale giving us a better shot at being able to understand it
- Nanosensors are small, durable, and portable
- These devices cause minimum disruption to the analyte allowing us to get a closer and better understanding of its real state and nature
- These are capable of performing multiple functions simultaneously
- They have a lower power consumption and higher accuracy than generic devices
Okay, now that we’ve established that they’re great, now let’s understand how they work
There are multiple different variants of nanosensors co-relating to their respective function. However, for understanding they’re working, we will take a look at two types of nanosensors, chemical and mechanical.
Chemical nanosensors work by measuring the change in the electrical conductivity of the nanomaterial once an analyte has been detected. Nanotubes and nanowires would serve as excellent examples of chemical nanosensors as they can act both as electrical wires and transducers*
Mechanical nanosensors work the same way, by detecting a change in electrical conductivity of the nanomaterial but using a different mechanism. These nanomaterials change their electrical conductivity when the material is physically manipulated, inflicting a detectable response. E.g., If a molecule of NO2 (Nitrogen Dioxide) is passed through a carbon nanotube, then it will take away an electron from the nanotube to complete its valence shell, and in turn, the transfer would create an electrical impulse which would be analyzed and noticed by the nanosensor as it is now less conductive.
So what are you saying…?
To generalize the idea, nanosensors work by looking for either a change or differentiation in/about the analyte. E.g., nanosensors being used for purposes of toxic gas detection tend to look for distinction in the mass of the atoms of gas.
The signals given off by nanosensors are measured similar to standard DC current, though since the current given off by these little guys is also nano, it is deficient in voltage; thus, usually requires the installation of special software and equipment to analyze it
Nanofabrication is the process of producing…well anything nano. Nanosensors are also produced using the process of nanofabrication. As of today, there are mainly three forms, and a billion hypothesize of nanofabrication used in the production of Nanosensors:
- Top-down lithography: Top-down lithography is the most common way used to produce nanosensors. Top-down lithography is similar to what Michelangelo did when he sculpted the statue of David. He took a large lock of some material and carved it out into the desired form, similarly, in top-down lithography, the production starts upon taking a larger block of material and carving it into the desired form
- Bottom-up method: This method involves assembling the sensors out of individual atoms or molecules. This consists of moving atoms of a particular substance one by one into specific positions
- Self Assembly: Self-assembly is also known to be the fastest method of nanofabrication. This involves “growing nanosensors.” As the name implies, self-assembly is a process in which a system with preexisting components forms an organized structure or pattern as a result of local interactions without external direction.
Everything has its flaws
The flaw with nanofabrication tends to be the fact that the equipment involved and the general process is costly or takes a long time. If one chooses the lithographic method to produce sensors, then the production will be efficient though the process would be expensive. On the flip side, if one decides to indulge in the bottom-up method, the output would be cost-efficient but would take a long time. The molecular self-assembly process is a process that cannot be directly controlled, which may arise issues.
Potential Ideas For Improvement:
Before we begin diving into possible improvement ideas, we need to establish what it is that is causing all those flaws. Why does the top-down process cost so much? Why does bottom-up take too much time? These may come off as general questions though we need to look at their fine print. I believe that once we establish the fine print for these processes, we should begin trying to process the “pros” from these different methods and assimilate them into one efficient method, or stage them. By “staging” them, I mean to imply using different techniques for different stages for production.
Some cool past developments:
- Scientists were able to capture the presence of a cirrhotic liver’s biomarker in a patients breather using nanosensors to act as transducers
- Scientists were able to detect the signs and symptoms of breast cancer from a blood culture eight months before visible signs
- Nanosensors have previously been known to be able to detect the presence of a tumour using fluorescence characteristics of CdSe (cadmium selenide) quantum dots
Analyte: a substance whose chemical constituents are being identified and measured
Transducer: a device that converts variations in a physical quantity, such as pressure or brightness, into an electrical signal, or vice versa.