Nano sensors and Nano fabrication — A World so Small, Made Big

This small piece of technology may be small but it is big when it comes to new emerging technologies out there. As we know, in our new day and age, the smaller the piece of technology, the more practical it is, and easy to use. Nanosensors are the future of our environment, medicine, and engineering. In this article, you will learn all types of information about nano sensors, such as what they are, why they are important, how they work, how they are built in terms of nanofabrication, the issues with nanofabrication, and how to improve them.

To understand what we are talking about further on, you need to understand what a nano sensor is, and how they came to be.

A nanosensor is a chemical or mechanical sensor that can be defined as a device that is capable of conveying data and information about the behavior and characteristics of nano particles at the nano scale level to the macroscopic level, visible to the naked eye.They are used to detect the minuscule presence of chemical species and nano particles, or to monitor physical parameters such as temperature, on the nano scale. Their job is to detect the presence and behaviors of nano particles or molecules. They are able to:

  • Detect types of gases in the environment
  • Types of organic molecules nearby
  • Pathogens and other Microorganisms
  • Change in PH, temperature, moisture and conductivity, pressure /flow, stress, position of nano particles, and forces
  • And more.
Subcategories that nano sensors fall under, as they observe different things.

Nanosensors measure objects in nano meters(nm), or billionths of a meter. At a scale this small, surface area greatly affects the material’s behavior than larger objects which results in properties like conductivity, reflectivity, and magnetism changing compared to larger bodies. Nanosensors detect these minuscule changes very quickly.

The term nano in nanosensor refers not to the size of the sensor (although some can be in the nano scale) but it rather signifies that the sensor itself operates at the nano scale. Nanosensors are devices that are used to measure very, very small quantities, that the human brain can not even begin to imagine.

Most researchers in the nanotechnology field spend their time working with materials between 10 and 100 nm across.To put this into perspective, a human hair is approximately 80,000- 100,000 nm wide. That is really small.

These sensors can be classified into either those that have nano scale dimensions or those that perform nano scale measurements. There are two types of nano sensors that are mainly used:

  • Active: Rely on an external power source to operate, which are able to send signals remotely.
  • Passive: Rely on factors in its environment to operate, and observations such as color, radiance, and opacity.

How is something so small in our world, be so big in an emerging world of new technologies and society?

Nanosensors are important to our increasingly advancing world in technology as it opens many new possibilities and fields of devices and new technology that further our knowledge of the world around us. This device can easily interact with particles at the nano level which helps with observing the unique processes that occur that can not be seen at the macro level. There are many positives to nano sensors that include:

Nano sensors are highly sensitive which allows for an increase of precision and accuracy.They are small, durable, light and portable; they have low power consumption; they require less of the material analyzed which causes minimum disturbance to the observed material or process; their low response time allows them to do real-time analysis which is useful in many fields; it can detect multiple things at the same time allowing for multiple functions. All of these strengths compared to other sensors give this device a lot of potential that can be used to further research and an increase of innovation in a number of fields.

As you can see, Nanosensors aid in the progression of fields such as medical technology; precision agriculture; urban farming; plant nano bionics; prognosis and diagnostics; and many industrial applications.

Some of the applications of nano sensors

A great example of a device that uses nano sensors would be this nano-sized doughnut-shaped chip that attaches to the end of the catheter could improve the way doctors peek inside our circulatory systems.

They are used:

  • To detect various chemicals in gases for pollution monitoring
  • For medical diagnostic purposes either as blood borne sensors or in lab-on-a-chip type devices
  • To monitor physical parameters such as temperature, displacement, and flow
  • As accelerometers in MEMS(micro-electromechanical system) devices like airbag sensors
  • To monitor plant signaling and metabolism to understand plant biology
  • To study neurotransmitters in the brain for understanding neurophysiology

There are many more applications to nano sensors, which is why they are so important to our evolving world in technology.

The components of a sensor system must include an analyte, sensor, transducer, and a detector, that allows for feedback from the detector to the sensor. The main goal behind the design of a sensor is to have accuracy, sensitivity and for it to be easily executed.

Chemical and mechanical nano sensors are made to detect/ measure/monitor the electrical changes of nano materials. For example, in carbon nano-based tubes, a molecule of nitrogen dioxide (NO2) is present, it will strip an electron from the nano tube, which decreases the conductivity of the nano tube; this change in conductivity is detected by the nano sensors. By treating the nano tubes with various coating materials, they can be designed to be sensitive to certain molecules and immune to others, making it easier to detect specific molecules.

An image demonstrating the working principle of CNT-based physical, chemical and biological nano sensors.

You may ask, how accurate can the nano sensors really be?

Nano sensors have been developed/ designed to the point of measurement at the single-molecule level.

How do they create any type of nanotechnology to begin with?

Nanofabrication is the design and manufacture of devices with dimensions measured in nano meters( One nano meter is a millionth of a millimeter.) This is the process in which nano sensors and other nano structures are made. There are two main methods of nano fabrication; top down fabrication and bottom up fabrication. The top down fabrication approach is a subtractive process in which existing material is reduced in complexity to produce features of a controlled shape and size that is in the nano-scale form. The bottom up fabrication approach is an additive process in which atoms and molecules are placed one by one and are used to build up the desired nano structure (e.g. nano wires, nano dots).

Basically, a material is gradually built from scratch, literally at the molecular level.

The most common type of nano fabrication process is the top down fabrication process as it has a lot of advantages such as the ability to put the desired feature / entity in an exact location, which is also called nano lithography. The top down fabrication method mostly uses etching to fabricate the nano sensors. In this process, the material is protected by a mask that is required for the nano structure, that they use to etch away any exposed material. There are many different chemical and mechanical methods to etching. This can be done chemically using acids or mechanically using ultraviolet light, x-rays or electron beams; depending on the level of resolution required for the nano structure etching of the base material.

With any manufacturing process, problems and challenges always arise, because nothing can truly be perfect.

Nano fabrication comes with many positives; for example, as the complexity of chain molecules is rearranged and reduced, a given material may become:

  • Stronger
  • More flexible
  • More durable
  • Lighter-weight
  • Better able to resist temperature extremes
  • More resistant to environmental and other types of corrosion

However, with many positives must come some negatives. What are the problems with nano fabrication to begin with?

Problems with the approaches of nano fabrication arise, as nothing can be perfect, even with a near perfect product. A logistical problem is that equipment/facilities are becoming increasingly expensive, thus the nano-sensors themselves are very expensive, as well. That’s how the industry makes money.

The top down fabrication method is more efficient and takes less time than the bottom up fabrication method, but the problem is that the equipment is very expensive. However, the bottom up fabrication method is cost effective, but is not currently effective and takes a much longer period to fabricate the nano structure than the top down fabrication method.

Improving the bottom-up fabrication method is probably the easiest, and more efficient approach to make nano fabrication better, which is why most companies try to use this approach. Many scientists are currently working on using the bottom up fabrication method to make it self-assembling and eventually eliminate human error all together, in order to make it more efficient, and reduce the production time to a fraction. I believe that combining the better parts of both the top down and bottom up fabrication processes can be way more effective to create an even faster and more efficient process to utilize.

This can greatly increase the use of nanotechnology that is already continuously being more used in many fields which improves all quality of life and can revolutionize many new industries that work within the nano scale.

Thank you for reading my article, I hope you enjoyed learning more about nanosensors and nanofabrication:)

Sharing my insights and thoughts about the world we all live in today.