Integration of Different Graphene Nanostructures with PDMS to Form Wearable Sensors

Abstract

This paper presents a substantial review of the fabrication and implementation of graphene-PDMS-based composites for wearable sensing applications. Graphene is a pivotal nanomaterial which is increasingly being used to develop multifunctional sensors due to their enhanced electrical, mechanical, and thermal characteristics. It has been able to generate devices with excellent performances in terms of sensitivity and longevity. Among the polymers, polydimethylsiloxane (PDMS) has been one of the most common ones that has been used in biomedical applications. Certain attributes, such as biocompatibility and the hydrophobic nature of PDMS, have led the researchers to conjugate it in graphene sensors as substrates or a polymer matrix. The use of these graphene/PDMS-based sensors for wearable sensing applications has been highlighted here. Different kinds of electrochemical and strain-sensing applications have been carried out to detect the physiological signals and parameters of the human body. These prototypes have been classified based on the physical nature of graphene used to formulate the sensors. Finally, the current challenges and future perspectives of these graphene/PDMS-based wearable sensors are explained in the final part of the paper.

Keywords: graphene; nanoplatelets; reduced graphene oxide; sensors; wearable.

Figure 1

Use of different kinds of graphene nanomaterials for electrochemical [104] and strain-sensing [105] applications by integrating them with PDMS. Reproduced from Kwon, S.S., Shin, J.H., Choi, J., Nam, S., and Park, W.I., 2017. “Defect-mediated molecular interaction and charge transfer in graphene mesh–glucose sensors”. ACS Applied Materials & Interfaces, 9(16), pp. 14216–14221; “A graphene-based electrochemical device with thermoresponsive microneedles for diabetes monitoring and therapy”. Nature nanotechnology, 11(6), pp. 566–572; and Irani, F.S., Shafaghi, A.H., Tasdelen, M.C., Delipinar, T., Kaya, C.E., Yapici, G.G., and Yapici, M.K., 2022. “Graphene as a Piezoresistive Material in Strain Sensing Applications”. Micromachines, 13(1), p. 119.

Figure 2

(a) Different layers of the chip. (b) Working process of the devices [123]. Reproduced from Pu, Z., Zou, C., Wang, R., Lai, X., Yu, H., Xu, K. and Li, D., 2016. “A continuous glucose monitoring device by graphene modified electrochemical sensor in microfluidic system”. Biomicrofluidics, 10(1), p. 011910.

Figure 3

Illustration of the fabrication steps of (A) electroactive rGO-based nanocomposites and (B) flexible glucose biosensors [124]. Reproduced from Xu, M., Zhu, Y., Gao, S., Zhang, Z., Gu, Y. and Liu, X., 2021. “Reduced graphene oxide-coated silica nanospheres as flexible enzymatic biosensors for detection of glucose in sweat”. ACS Applied Nano Materials, 4(11), pp. 12442–12452.

Figure 4

Schematic diagram of the fabrication of the rGOFF/PDMS-based pressure sensors [132]. Reproduced from Jiang, X., Ren, Z., Fu, Y., Liu, Y., Zou, R., Ji, G., Ning, H., Li, Y., Wen, J., Qi, H.J., and Xu, C., 2019. “Highly compressible and sensitive pressure sensor under large strain based on 3D porous reduced graphene oxide fiber fabrics in wide compression strains”. ACS Applied Materials & Interfaces, 11(40), pp. 37051–37059.

Figure 5

Illustration of the flow of fabrication steps of piezoresistive multilayered GNP/PDMS foams [144]. Reproduced from Rinaldi, A., Tamburrano, A., Fortunato, M. and Sarto, M.S., 2016. “A flexible and highly sensitive pressure sensor based on a PDMS foam coated with graphene nanoplatelets”. Sensors, 16(12), p. 2148.

Figure 6

Schematic diagram of the structure of GQDs/PDMS-based e-skin [147]. Reproduced from Xu, Z., Wu, C., Li, F., Chen, W., Guo, T. and Kim, T.W., 2018. “Triboelectric electronic-skin based on graphene quantum dots for application in self-powered, smart, artificial fingers”. Nano Energy, 49, pp. 274–282.