Sensors and

Instrumentation Digital Assignment Topic: Nanoelectronics

– Role of nanosensors

By:

Rishu Mishra 15BEC0187 - (TA1)

- Role of nanosensors

Introduction:

Nanoelectronics refer to the use of nanotechnology in electronic components. The term covers a diverse set of devices and materials, with the common characteristic that they are so small that inter-atomic interactions and quantum mechanical properties need to be studied extensively. Some of these candidates include: hybrid molecular/semiconductor electronics, one-dimensional nanotubes/nanowires, or advanced molecular electronics.

Nanosensors are any biological, chemical, or surgical sensory points used to convey information about nanoparticles to the macroscopic world. Their use mainly includes various medicinal purposes and as gateways to building other Nano products, such as computer chips that work at the nanoscale and Nano robots. There are several ways being proposed today to make nanosensors

Nanoelectronics increase the capabilities of electronic devices such as improving the display screens on electronics devices by decreasing the weight and thickness of the screens and reducing the consumption of power There are many approaches to Nano electronics. Few of them includes, Nanofabrication which involves transistor operation based on a single electron. Molecular electronics, in which a molecular level diode / transistor might be synthesized by organic chemistry. Nanoionics, which deals with the transport of ions and Nano photonics, deals with the behavior of light on the nanoscale. Nanosensors, convey information about nanoparticles. Many scientific breakthroughs in Nanotechnology has been contributed by Nanosensors. Different types of sensors are built from nanomaterials to detect chemical vapors, to detect range of chemical vapors, to sense bacteria or viruses, to detect single molecules, to help pharmaceutical companies in production of drugs. The Uses of Nanosensors: Scientists and engineers are collaborating across disciplines to develop and network miniaturized intelligent nanosensors that can rapidly and remotely detect change in their surroundings. These sensors have a wide range of potential applications: environmental, medical, military and transportation.

Current high-technology production processes are based on traditional top down strategies, where nanotechnology has already been introduced silently. The critical length scale of integrated circuits is already at the nanoscale (50 nm and below) regarding the gate length of transistors in CPUs or DRAM devices.

1. Computers: Nanoelectronics holds the promise of making computer processors more

powerful than are possible with conventional semiconductor fabrication techniques. A number of approaches are currently being researched, including new forms of nanolithography, as well as the use of nanomaterials such as nanowires or small molecules in place of traditional CMOS components. Field effect transistors have been made using both semiconducting carbon nanotubes and with heterostructured semiconductor nanowires.

Attaching a single particle onto the end of a carbon nanotube and measuring the vibrational frequency of the nanotube both with and without the particle. The discrepancy between the two frequencies also allowed the researchers to measure the mass of the attached particle. projected products most commonly involve using nanosensors to build

smaller integrated circuits, as well as incorporating them into various other commodities made using other forms of nanotechnology for use in a variety of situations including transportation, communication, improvements in structural integrity, and robotics. 2. Energy Production:

Research is ongoing to use nanowires and other nanostructured materials with the hope to create cheaper and more efficient solar cells than are possible with conventional planar silicon solar cells. It is believed that the invention of more efficient solar energy would have a great effect on satisfying global energy needs.

The average person's body could, theoretically, generate 100 watts of electricity (about 2000 food calories per day) using a Bio-Nano generator. However, this estimate is only true if all food was converted to electricity, and the human body needs some energy consistently, so possible power generated is likely much lower. The electricity generated by such a device could power devices embedded in the body (such as pacemakers), or sugar-fed Nano robots. Much of the research done on Bio-Nano generators is still experimental, with Panasonic's Nanotechnology Research Laboratory among those at the forefront.

3. Medical Diagnostics:

There is great interest in constructing Nano electronic devices that could detect the concentrations of biomolecules in real time for use as medical diagnostics, thus falling into the category of Nano medicine. A parallel line of research seeks to create Nano electronic devices which could interact with single cells for use in basic biological research. These devices are called nanosensors. Such miniaturization on Nano electronics towards in vivo proteomic sensing should enable new approaches for health monitoring, surveillance, and defense technology. Medicinal uses of nanosensors mainly revolve around the potential of

nanosensors to accurately identify particular cells or places in the body in need. By measuring changes in volume, concentration, displacement and velocity, gravitational, electrical, and magnetic forces, pressure, or temperature of cells in a body, nanosensors may be able to distinguish between and recognize certain cells, most notably those of cancer, at the molecular level in order to deliver medicine or monitor development to specific places in the body

One example of nanosensors involves using the fluorescence properties of cadmium selenide quantum dots as sensors to uncover tumors within the body. By injecting a body with these quantum dots, a doctor could see where a tumor or cancer cell was by finding the injected quantum dots, an easy process because of their fluorescence. Developed Nano sensor quantum dots would be specifically constructed to find only the particular cell for which the body was at risk. A downside to the cadmium selenide dots, however, is that they are highly toxic to the body.

Another use of nanoparticles is in the detection of volatile organic compounds (VOCs). Researchers have found that by embedding metal nanoparticles made of substances such as gold in a polymer film, you create a VOC Nano sensor. 4. Chemical sensors:

They too, have been built using nanotubes to detect various properties of gaseous molecules. Carbon nanotubes have been used to sense ionization of gaseous molecules while nanotubes made out of titanium have been employed to detect atmospheric concentrations of hydrogen at the molecular level. Many of these involve a system by which nanosensors are built to have a specific pocket for another molecule. When that particular molecule, and only that specific molecule, fits into the Nano sensor, and light is shone upon the Nano sensor, it will reflect different wavelengths of light and, thus, be a different color in a similar fashion, Flood et al. have shown that supramolecular host-guest chemistry offers quantitative sensing using Raman scattered light as well as SERS.

5. Sensors using semiconductor nanowire detection elements: These sensors are capable of detecting a range of chemical

vapors. When molecules bond to nanowires made from semiconducting materials such as zinc oxide, the conductance of the wire changes. The amount that the conductance changes and in which direction depends on the molecule bonded to the nanowire. For example, nitrogen dioxide gas reduces how much current the wire conducts, and carbon monoxide increases the conductivity. Researchers can calibrate a sensor to determine which chemical is present in the air by measuring how the current changes when a voltage is applied across the nanowire.

6. Nano cantilevers:

These devices are being used to develop sensors that can detect single molecules. These sensors take advantage of the fact that the Nano cantilever oscillates at a resonance frequency that changes if a molecule lands on the cantilever, changing its weight. Coating a cantilever with molecules, such as antibodies, that bond to a particular bacteria or virus determines what bacteria or virus will bond to the cantilever.

Production Methods: 1. There are currently several hypothesized ways to produce nanosensors. Top-down

lithography is the manner in which most integrated circuits are now made. It involves starting out with a larger block of some material and carving out the desired form. These carved out devices, notably put to use in specific microelectromechanical systems used as micro sensors, generally only reach the micro size, but the most recent of these have begun to incorporate Nano sized components.

2. Another way to produce nanosensors is through the bottom-up method, which involves assembling the sensors out of even more minuscule components, most likely individual atoms or molecules. This would involve moving atoms of a particular substance one by one into particular positions which, though it has been achieved in laboratory tests using tools such as atomic force microscopes, is still a significant difficulty, especially to do en masse, both for logistic reasons as well as economic ones. Most likely, this process would be used mainly for building starter molecules for self-assembling sensors.

Figure 1.Credit: Courtesy of R. Bashir and M. A. Alam of Purdue University; image drawn by Seyet, LLC

(A) An example of a DNA molecule used as a starter for larger self-assembly. (B) An atomic force microscope image of a self-assembled DNA Nano grid. Individual DNA tiles self-assemble into a highly ordered periodic two-dimensional DNA Nano grid. 3. The third way, which promises far faster results, involves self-assembly, or “growing”

particular nanostructures to be used as sensors. This most often entails one of two types of assembly. The first involves using a piece of some previously created or naturally formed nanostructure and immersing it in free atoms of its own kind. After a given period, the structure, having an irregular surface that would make it prone to attracting more molecules as a continuation of its current pattern, would capture some of the free atoms and continue to form more of itself to make larger components of nanosensors.

Economic Impacts: First, however, Nano sensor developers must overcome the present high costs of production in order to become worthwhile for implementation in consumer products. Additionally, Nano sensor reliability is not yet suitable for widespread use, and, because of their scarcity, nanosensors have yet to be marketed and implemented outside of research facilities. Consequently, nanosensors have yet to be made compatible with most consumer technologies for which they have been projected to eventually enhance. Social Impacts: The advancement in detecting and sensing different biological and chemical species with increased capacity and accuracy may transform societal mechanisms that were originally designed on uncertainty and imprecise information.

For example, the ability to measure extremely low amounts of air pollutants or toxic materials in water raises questions and dilemmas of risk thresholds especially if the advancement of such technologies outpaces the ability of the public to respond. As another example, medical sensors will not only help in diagnoses and treatment but may also predict the future profile of an individual. This will add to the information used by health insurance companies to grant or deny coverage. Other social issues resulting from the widespread use of nanosensors and surveillance devices include privacy invasion and security issues.