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Materials Science in Additive Manufacturing Materials for 3D-printed electrodes

Hydrogels can be deformed and adhered to tissues. of the electrodes. We believe that continuous explorations
However, hydrogels are water-swellable crosslinked will give rise to flexible electrodes with higher resolutions
polymers, and the loss of water inevitably leads to and more channels, which can facilitate the delivery of
deterioration of mechanical properties, making prolonged precise and sensitive data.
use in an anhydrous environment challenging. Elastomeric
materials formed by crosslinking polymer chains exhibit In terms of technology, it is necessary to continuously
better mechanical properties and environmental stability improve the resolution and material compatibility with
without relying on solvent swelling. Thus, elastomeric 3D printing technology to meet the growing demand for
materials are more suitable for 3D printing technologies using 3D-printed flexible electrodes in various medical
such as FDM, which rely on high-temperature conditions scenarios. In addition, combining 3D printing technology
for printing and molding. Thermoplastic PU (TPU) is with photolithography and screen printing provides an
a common polymer used in FDM printing due to its impetus to the development of high-precision, multi-
excellent flexibility and stable melting temperature [142] . In channel flexible electrodes, which are promising tools for
Hu et al.’s study, TPU-based electrode filaments that can be acquiring and stimulating refined physiological signals.
used for FDM printing were prepared by mixing different Future research could also consider optimizing the
active materials (lithium iron phosphate, lithium titanate, structural design of flexible electrodes to make 3D-printed
nickel cobalt manganese oxide, or graphite) with TPU and flexible electrodes more personalized and compatible with
conductive additives in dimethylformamide (Figure 6E). clinical needs and applications.
The flexible electrodes with complex structures prepared In the future, clinical trials should be conducted to
by FDM printing exhibit excellent print stability and investigate innovative materials, technologies, and designs.
mechanical properties [143] . It is also necessary to promote the adaptation of flexible
6. Conclusion and perspectives electrodes into clinical use by improving the performance of
flexible electrodes, expanding the function of electrodes, and
Flexible electrodes serve diverse purposes in both reducing the production cost. These desirable features will
medical research and clinical practice. Extracorporeal also indirectly broaden their applications in the medical field.
flexible medical electrodes enable the monitoring of
human electrocardiographic signals for early diagnosis Acknowledgments
and risk prediction, allowing patients to receive timely
cardiovascular interventions and reducing the occurrence The authors acknowledge the support received from
of emergent cardiovascular events. Implantable flexible Microsoft Bing’s chat mode and BioRender.com. The
electrodes allow real-time transmission of electrical signals middle image in Figure 1 was created using Microsoft
within the brain and are an important component of brain- Bing’s chat mode, while other elements in Figures 1 and 2
computer interfaces. They serve diagnostic and therapeutic were created using BioRender.com.
purposes and contribute to the study of functional brain Funding
regions. Furthermore, flexible electrodes have been
explored in studies involving nerve conduit scaffolds to This work was financially supported by the National
promote tissue repair and regeneration. Key Research and Development Program of China
The continuous optimization of materials and (2021YFF1200800); Sichuan Science and Technology
improvement of manufacturing technology is significant Program (2021JDTD0001); The National Natural Science
for generating advanced medical flexible electrodes. In Foundation (32271468); Natural Science Foundation of
terms of materials, more comprehensive research on Sichuan Province (2022NSFSC1453); and Innovation
existing materials is required. For example, through doping, Research Project of Sichuan University (2022SCUH0046).
modification, and material composites, it is possible to Conflict of interest
enhance the conductivity and stability of electrically
conductive materials or the flexibility and tensile properties The authors declare no conflict of interest.
of flexible materials. In addition, we need to improve Author contributions
the processability of materials and broaden the range of
materials compatible with 3D printing technologies. At Conceptualization: Maling Gou
the same time, we also need to continually develop new Writing – original draft: Yiting Huang, Qi Zhu, Haofan Liu,
conductive materials with excellent biocompatibility and Ya Ren
cyclic stability, which can be used to create more flexible Writing – review & editing: Yiting Huang, Maling Gou, Li
electrodes for in vivo implantation and prolong the lifespan Zhang

Volume 2 Issue 4 (2023) 11 https://doi.org/10.36922/msam.2084