The field of nanophotonics examines the interactions between light and matter on a very small scale, known as the nanoscale. It encompasses a variety of complex physical phenomena that are beyond the limitations of diffraction and offers novel prospects for applications in optical switching, light absorption, luminescence, sensing and media transmission technologies.
What is the mechanism behind nanophotonic sensors?
Nanophotonic sensors utilize the interactions between light and matter to detect physical, chemical or biological occurrences at extremely small scales. These structures can be made from a variety of materials, including metals, semiconductors and dielectrics. When light interacts with these devices, it can be absorbed, scattered or reflected. The way that light interacts with the structures depends on the properties of the material, as well as their size and shape.
These sensors have demonstrated significant potential in biosensing, surpassing the limitations of existing bioanalytical techniques in terms of affordability, ease of use, sensitivity and compactness. They are capable of detecting alterations in the refractive index or optical absorption of a nanostructure. The refractive index of a material is a measure of how much light is bent as it passes through the material. The interaction between light and the nanostructure leads to alterations in the refractive index or optical absorption, which can be detected by observing variations in the resonance wavelength or transmission level of the sensor.
Infrared-guided-wave nanophotonic sensors utilize the detection of evanescent fields to recognize biological analytes. The disturbances created by these substances in the surrounding environment can be identified by measuring alterations in the cladding's optical absorption or refractive index. This allows for the identification and measurement of the presence and amount of the desired substance. Nanophotonic sensors can also be used to detect changes in the electrical properties of a material. This can be done by measuring the way that light interacts with the material when an electric field is applied.
How do nanophotonic sensors compare with other similar sensors?
Nanophotonic sensors can be compared with other similar sensor types such as electrical, chemical and fiber optical sensors. Electrical sensors rely on changes in electrical properties like conductivity, capacitance or resistance to detect a target element. Examples include pH meters (measure acidity), strain gauges (measure pressure or force) and gas sensors (detect presence of specific gases). Chemical sensors use chemical reactions to detect specific molecules. Examples include biosensors (detect biological molecules like enzymes or antibodies) and electrochemical sensors (measure changes in ionic activity). Fiber optic sensors (use light traveling through fibers for various measurements) and surface plasmon resonance (SPR) sensors (detect changes in biomolecule binding on a metal surface). Here are the advantages and disadvantages of nanophotonic sensors in comparison to these sensors:
Advantages:
- High sensitivity: Nanophotonic sensors can detect incredibly minute changes in their environment due to their interaction with light at the nanoscale. This allows them to pick up on very faint signals, making them ideal for applications like early disease detection or trace gas identification.
- Low limit of detection (LOD): Following from the high sensitivity, nanophotonic sensors can achieve very low LODs, meaning they can detect extremely small quantities of a target analyte. This is crucial for applications where even tiny amounts can have a significant impact, like biomolecule detection in medical diagnostics.
- Small size and miniaturization: The ability to manipulate light at the nanoscale allows for incredibly compact sensor designs. This makes them perfect for integration into microfluidic chips or other miniaturized devices.
- Multiplexing capability: Nanophotonic sensors can be designed to detect multiple analytes simultaneously. This is achieved by incorporating different functionalities within the sensor structure, allowing for a broader range of detection in a single platform.
- High stability and immunity to EMI: Nanophotonic sensors are generally less susceptible to electromagnetic interference (EMI) compared to electrical sensors. This makes them more reliable for use in environments with electrical noise.
Disadvantages:
- Fabrication complexity: Manufacturing nanophotonic sensors often involves complex and precise techniques like nanofabrication. This can make them more expensive to produce compared to some traditional sensors.
- Limited range of analytes: While some nanophotonic sensors can be designed for broad detection, some may be highly specific to certain types of analytes. This can limit their applicability in some situations.
Applications of nanophotonic sensors
Nanophotonic sensors find diverse uses in the fields of food safety, healthcare, pharmaceuticals, environmental monitoring and the forensics sector. Deployment for food analysis is increasing due to their affordability, rapid detection, heightened sensitivity and specificity. These sensors have the ability to identify impurities from different types of food, making them a flexible instrument in the food processing business.
Nanophotonic sensors made with nanoplasmonic materials can be employed to track cell proliferation in living cells. The sensors are covered with a layer of silicon dioxide and gold, which function as optical antennae to perceive alterations in nanoplasmonic resonances resulting from cell attachment. Such sensors have the ability to detect and monitor cell growth without the use of chemical labels. This preserves the viability of the cells and offers a platform for long-term monitoring that does not require labeling.
Evanescent sensing-based nanophotonic biosensors have become promising options in the field of environment monitoring systems. This is because they possess the ability to detect without the need for labels and exhibit a high level of sensitivity. Moreover, these sensors have the capability to detect minuscule quantities of contaminants, rendering them an optimal instrument for early warning systems. Nanophotonic sensors also present a viable and advantageous approach for the quick and precise detection of viral infections.
Conclusion
Nanophotonic sensors employ the interactions between light and matter to detect physical, chemical or biological events at nanoscale level. When light comes into contact with these structures, it can either be absorbed, scattered or reflected. They offer a powerful and promising technology for various sensing applications. Their high sensitivity, miniaturization capabilities and potential for multiplexing make them attractive for future advancements in fields like healthcare, environmental monitoring and food safety. However, their fabrication complexity and potentially limited range of analytes are aspects to consider when choosing the most suitable sensor for a specific application.
