Wearable device applications have ushered in a new era of human-computer interaction with a variety of purposes, underlying concepts, and forms. These devices have widespread uses in medical and health domains such as physiological signal assessment, athletics, and pollution detection.
Study: Synthesis of a nitrogen doped reduced graphene oxide based ceramic polymer composite nanofiber film for wearable device applications. Image Credit: magic pictures/Shutterstock.com
Developing an effective electrode with optimum dielectric permittivity for wearable device applications, however, remains a major challenge.
A recent study published in Scientific Reports addresses this issue by fabricating a piezoelectric composite nanofiber film-based electrode for novel wearable device applications.
Materials for Wearable Device Applications: Overview and Challenges
Piezoelectric composites based on polymeric materials and ceramics have gained significant interest for wearable device applications because of their excellent mechanical and electrical qualities, such as adaptability, dielectric properties, and resilience. The electrical characteristics of untreated materials can be improved by incorporating piezoelectric ceramics into composite materials.
Although piezoelectric composite materials have been successfully developed for wearable device applications, their resistive characteristics restrict their ability to improve piezoelectric capabilities. Conductive materials may be introduced into piezoelectric composites to increase their electrical characteristics, overcoming these constraints.
Two-dimensional reduced graphene oxide (rGO) is commonly used as a conductive substance in wearable device applications. It may be mixed with other materials to enhance mechanical and electrical qualities.
Consequently, incorporating rGO into piezoelectric materials can increase their piezoelectric characteristics. However, numerous defects are formed during the reduction reaction of rGO, compromising its electron transport characteristics.
These defects may be very damaging to piezoelectric-based wearable device applications since they disturb the electric field. To compensate for the reduced conductive characteristics, nitrogen may be incorporated into two-dimensional rGO, resulting in N-rGO with improved electrical properties.
Piezoelectric Nanofiber Films: The Future of Wearable Device Applications
Piezoelectric nanofiber films made from copolymer and ceramic materials have various benefits over conventional composites, including adaptability and dielectric properties. A nanofiber film is more flexible than other composites and ceramic polymers because of its large aspect ratio.
Although many techniques can be used to create piezoelectric nanofiber films for wearable device applications, the electrospinning method is commonly used because it offers several benefits over other physical production methods.
Electrospinning is a process that uses an electric field to create nanofibers of polymeric materials, ceramics, and metals. This method can create nanofibers from complicated compounds and work at low temperatures.
Moreover, highly conducting N-rGO and piezoelectric hybrid nanofibers can be thoroughly combined during the preparation procedure before electrospinning. Consequently, N-rGO doped piezoelectric composite nanofibers suitable for various wearable device applications can be easily fabricated.
Interdigital Electrodes for Wearable Device Applications
Almost all wearable device applications have a planner-type electrode structure, and traditional vertical-type electrodes cannot be used in next-generation wearable device applications. It is well established that piezoelectric nanofibrous films with planner-type electrodes offer unique electrical capabilities for a wide range of wearable device applications.
This study created interdigital planner-type electrodes and applied them on N-rGO-doped piezoelectric hybrid nanofiber films for wearable device applications.
The researchers selected the synthetic N-rGO for enriching piezoelectric composite nanofibers because it has higher conductivity than rGO. Nitrogen is essential for eliminating flaws from the rGO surface. As a result of this higher conductance, the floating electrode properties in piezoelectric composite materials can be improved.
The researchers used the conformal mapping procedure to extract various combinations of dielectric permittivity by simulating and calculating the functional dielectric properties of the as-prepared electrodes. These electrodes were also used to develop adaptable piezoelectric energy extractors for wearable device applications.
Important Findings of the Study
The floating electrode characteristics enhanced the nanofiber-based power generator created in this work and enhanced the output power. The output power was optimized by refining the manufacturing technique and the interdigital electrode architecture. The stored potential, open-circuit voltage and output power were found to be 3.78 V, 12.4 V, and 6.3 μW, respectively.
The overall dielectric permittivity of the piezoelectric hybrid nanofiber films was increased from 8.2 to 15.5 by including ceramics and N-rGO conductors. This enhanced effective dielectric constant is most likely due to enhanced electric flux intensity as a result of greater conductance.
Based on these results, it is plausible to conclude that interdigital electrodes composed of N-rGO-doped piezoelectric nanofiber films have a high potential for use in a variety of wearable device applications in the future.
Ji, J.-H. et al. (2022). Synthesis of a nitrogen-doped reduced graphene oxide-based ceramic polymer composite nanofiber film for wearable device applications. Scientific Reports. Available at: https://www.nature.com/articles/s41598-022-19234-0