Nanosensors and the “internet of nanothings”

March 4th, 2019, Published in Articles: EngineerIT, Featured: EngineerIT

With the internet of things (IoT) expected to comprise 30-billion connected devices by 2020, one of the most exciting areas of focus is on nanosensors capable of circulating in the human body or being embedded in construction materials. Once connected, this “internet of nanothings” (IoNT) could have a huge impact on the future of industrial production, medicine, architecture, agriculture and drug manufacture.

Nanotechnology is defined as a technique used to enable the development of different devices at a scale ranging from one to many nanometres. A nanometre is 0,000001 of a millimetre, almost impossible to visualise.

The internet of nanothings is an interconnection between different nanodevices within existing networks. The nanomachine is basically integrated in order to execute various tasks. The difference is that it can connect components that are not possible to be connected with the conventional IoT. Nanosensors are being utilised for tracking various activities on a regular basis and monitoring various parameters in a very accurate manner.

The IoNT architecture includes various components such as:

  • Nanonodes: It is basically a device with the responsibility of executing the computational task as well as data transmission over very short distance networks with minimum use of memory.
  • Nanorouters: These have very large computation ability compared with nanonodes. They act as devices that aggregate the data supplied by the nanonodes.
  • Interface devices: This is a component that executes the task of aggregation of information is coming from nanorouters.
  • Gateway: This component is responsible for connecting entire nanothings to networks.

Research into nanosensors goes back to nature. As environmental pollution becomes an ever-greater concern, scientists are searching for new ways to monitor levels of potential contaminants. While there are already methods to monitor many pollutants, environmental chemists are designing nanomaterials that can detect these contaminants more inexpensively, efficiently, and selectively than old-school sensors. The small-scale structures are appealing because they are so tiny but have a very high surface area to volume ratio.

In a chemical sensor, increased surface area means more exposure to the target compound and greater ability to detect its presence at low concentrations. Nanomaterials, with their very fine structure, take this concept to an extreme level. Their increased surface area makes them both more efficient and more powerful. The nanoscale of this technology also means that it has ultra-low power consumption.

Nanomaterials are also easily customisable; their size, structure, and composition all influence their properties, and together, these variables produce a nearly endless array of combinations.

Fig. 1: Nanomaterials are easily customisable; their size, structure, and composition all influence their properties, and together, these variables produce a nearly endless array of combinations.

Scientists at the University of California-Berkeley drew inspiration from turkey skin, which changes colours when the animal becomes stressed or excited because it contains proteins arranged in nanostructured bundles. These researchers created a synthetic replica of the turkey skin’s nanoscale structure using phage, viruses that infect bacteria. They engineered the phage to recognise and bind to a specific compound; then, under the right chemical conditions, the phage assembled into a thin layer of nanostructured bundles. When the target compound was present in the atmosphere, it bound to the sensor and caused the nanobundles to change their spacing just as they had in the turkey skin. The result: a colour change in the detector’s surface, precisely quantified using an iPhone app that converts colour into a discrete value.

Despite the promise of sensors like these, more traditional methods for detecting the presence of certain molecules will likely stick around for a while. They’ve been more thoroughly tested than these cutting-edge nanosensors, and they’re ingrained into our society, used in devices found around us every day. For example, if you’ve ever had the airport security swab your hands in the airport security line, you’ve provided data for a major application of sensing technology. In the USA the Transport Security Agency (TSA) uses a technique known as ion mobility spectrometry (IMS) to detect trace residues of dangerous materials on the hands of travellers. IMS separates out molecules based on the speed with which they travel through a gas-filled chamber; molecules can be identified based on their relative mobility. Like nanosensors, IMS-based sensors can be portable and easy to use. However, nanosensors bring a higher level of specificity, sensitivity, and flexibility that traditional sensors lack, giving them the potential to greatly advance our environmental monitoring capabilities.

Already back in 2003, the George Washington University’s Professor David Nagel (PhD) said at a sensor conference that the trend toward the small began with the miniaturisation of macro techniques, which led to the now well-established field of microtechnology. Electronic, optical, and mechanical microtechnologies have all profited from the smaller, smarter, and less costly sensors that resulted from work with integrated circuits (ICs), fibre optics, other micro-optics, and micro-electromechanical systems (MEMS). As we continue to work with these minuscule building blocks, there will be a convergence of nanotechnology, biotechnology, and information technology, among others, with benefits for each discipline. Substantially smaller size, lower weight, more modest power requirements, greater sensitivity, and better specificity are just a few of the improvements we’ll see in sensor design.

Prof Nagel’s assertions that sensor design will fast move ahead is seen almost every day. The notion of smaller devices requiring less energy to operate was accelerated by the IoT. A recent example is how more MEMS packages are replaced and their functions taken over by a multi-sensor Nanusens chip using standard complementary metal-oxide-semiconductor (CMOS) plus a very simple and low-cost post-process to build MEMS sensors inside. This resulted in a cost advantage, leveraging the economy of scale behind CMOS, plus the ability to build sub-micron features and located attached to the electronics achieving small sizes, together with high performance and extreme reliability.

The Nanusens chip only increases slightly with every additional sensor function to accommodate additional control electronics. In addition, far less PCB estate is needed for the tiny, single chip solution compared to the PCB estate required for several MEMS packages. All this freed-up space can be used to increase the size of the battery or add a supercapacitor to extend the operational life and a better user experience.

When the IoT was first hyped, the sensor industry realised they were not right there to take advantage of the market opportunity. They have since fast moved ahead with very innovative developments. We have seen this at the CSIR with some exciting sensor developments ready to be industrialised. It is perhaps the development of the battery, or perhaps better expressed as the energy storage device, that need the push now.

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