Due to their unique characteristics, such as elasticity, affordability, manufacturing efficiency, and compatibility with a range of substrates, polymers are widely utilized in the manufacturing and design of sensors. Polymer chemistry has significantly assisted recent advancements in sensor technology with excellent sensitivity, specificity, and stability.
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The fields of polymer chemistry and sensor technology have seen massive development and advancement in recent years. Polymers are complex molecules made up of repeating units called monomers, and polymer chemistry is the study of the production, structure, characteristics, and uses of polymers. On the other hand, sensors are devices that can detect and identify environmental changes and transform that data into an optical or electrical signal.
Types of Polymers Used in Sensor Design
Polymers can be classified based on their properties and applications. The following are the types of polymers commonly used in sensor design and fabrication:
A category of polymers known as conducting polymers contains conjugated double bonds, which enable them to conduct electricity. Distinctive electrical and optical characteristics of these polymers have allowed them to be used in sensors. They can serve as transducers in sensors or as sensing materials.
Electroactive polymers can change their form, size, or reactivity in response to external stimuli like an electric field, temperature, or illumination. The capacity of these polymers to transform physical inputs into electrical signals has led to their use in sensors. Due to its electroactive qualities, polyethylene glycol diacrylate (PEGDA) can be utilized in pH sensors and glucose sensors.
Large amounts of water can be absorbed and retained in hydrogels (three-dimensional networks of hydrophilic polymers). These polymers have the potential for sensor applications due to their capability to expand in reaction to environmental alterations, such as pH, humidity, or the presence of certain ions.
Nanocomposite polymers include nanoscale fillers such as carbon nanotubes, graphene, or nanorods. These polymers' distinct electrical, photonic, and mechanical characteristics have allowed them to be used in sensors.
Role of Polymer Chemistry in Sensor Design and Fabrication
The development of sensors relies primarily on polymer chemistry. Due to their special characteristics, including elasticity, low cost, and flexibility, polymers are often employed in the design and manufacturing of sensors.
The synthesis of polymers with particular characteristics and configurations that can be modified for sensor applications is facilitated by polymer chemistry. The chemical structure of polymers can be altered to increase their sensitivity and selectivity towards certain analytes.
The molecular weight, shape, and functional groups of polymers can be controlled by the selection of monomers, initiators, and reaction conditions, which in turn, affects the sensor performance.
Polymers can be made more sensitive by adding chemical groups or moieties to the polymer backbone, a process known as functionalization. Polymers can be altered by incorporating different functional groups, such as amino, carboxyl, and hydroxyl. The immobilization of detecting molecules, including enzymes, antibodies, and DNA, using these functional groups can improve the accuracy and precision of sensors.
The fabrication of nanocomposite polymers is also significantly influenced by polymer chemistry. These nanocomposite polymers can be customized for certain sensor applications because of their distinctive mechanical, optical, and electrical characteristics. The sensor manufacturing and design field has been completely transformed by polymer chemistry, which has made it possible to develop sophisticated sensors.
Applications of Polymer Chemistry in Sensor Design and Fabrication
Polymer chemistry has a significant impact on the design and fabrication of sensors for various applications. By polymer chemistry, the choice of polymer can be modified to meet specific sensing requirements.
The advancement of biosensors, which are utilized to identify biological molecules like proteins, DNA, and enzymes, has been significantly assisted by polymer chemistry. Polyethylene glycol (PEG), which is biocompatible and can be altered to immobilize biomolecules, is one of the most frequently used polymers in biosensors. Additionally, due to their electroactive characteristics, conducting polymers like polypyrrole (PPy) and polyaniline (PANI) can be used as transducers in biosensors.
Polymer chemistry also plays an essential part in the development of gas sensors, which are used to detect carbon monoxide, nitrogen oxide, and hydrogen gases. Conductive polymers such as polypyrrole (PPy) and polythiophene (PTh) can be doped with gas-sensitive molecules to increase their selectivity towards certain gases.
Humidity sensors, which are used to gauge environmental humidity levels, are influenced by polymer chemistry. Absorbing water vapors enables hydrophilic polymers like polyethylene oxide (PEO) and polyvinyl alcohol (PVA) to serve as humidity sensors.
Polymer chemistry has also contributed to the development of temperature sensors used to measure environmental temperature fluctuations. Thermos-responsive polymers such as poly (N-isopropylacrylamide) (PNIPAAm) with reversible phase transition capabilities can be employed in temperature sensors.
Elastomeric polymers such as polydimethylsiloxane (PDMS) are also used in pressure sensors, which measure changes in environmental pressure due to their capacity to deform under pressure changes.
Limitations of Polymer Chemistry in Sensor Design
The use of polymers in sensor design has several limitations. Many polymers are not highly durable, especially when subjected to harsh conditions such as high temperatures, ultraviolet light, or chemicals. This can restrict their use in applications that demand long-term stability.
Moreover, while polymers can be functionalized to improve their selectivity towards specific analytes, they still could exhibit some cross-reactivity or lack of sensitivity towards molecules with identical structural properties, which limits their applicability in some applications. Lastly, achieving the necessary sensor performance could prove challenging due to the compatibility of particular polymers with specific manufacturing processes, such as thin-film deposition or lithography.
Polymer chemistry plays an essential role in developing sophisticated sensors with high sensitivity, selectivity, and durability through the development of conducting polymers, electroactive polymers, and hydrogels. The influence of polymer chemistry on sensor technology is substantial for many applications, including biosensors, gas sensors, pressure sensors, humidity sensors, and temperature sensors.
Undoubtedly, the design and fabrication of polymer-based sensors will continue to be an important field of study. New advances in polymer synthesis, fabrication, and functionalization are projected to contribute to further enhancements in sensor performance, precision, and sensitivity.
References and Further Reading
Elanjeitsenni, V. P., Vadivu, K. S., & Prasanth, B. M. (2022). A review on thin films, conducting polymers as sensor devices. Materials Research Express, 9(2), p. 022001. https://iopscience.iop.org/article/10.1088/2053-1591/ac4aa1
Liu, X., Zheng, W., Kumar, R., Kumar, M., & Zhang, J. (2022). Conducting polymer-based nanostructures for gas sensors. Coordination Chemistry Reviews, 462, p. 214517. https://www.sciencedirect.com/science/article/abs/pii/S0010854522001126
Mei, X., Ye, D., Zhang, F., & Di, C. (2022). Implantable application of polymer-based biosensors. Journal of Polymer Science, 60(3), pp. 328–347. https://onlinelibrary.wiley.com/doi/full/10.1002/pol.20210543
Ramanavicius, S., & Ramanavicius, A. (2022). Development of molecularly imprinted polymer based phase boundaries for sensors design (review). Advances in Colloid and Interface Science, 305, p. 102693. https://www.sciencedirect.com/science/article/abs/pii/S0001868622000951