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International Journal of Bioprinting 3D-printed bioelectronic devices

printing and high electrical conductivity for electronic temperature (Figure 2A). 69,71–73 Their ease of printability has
functionality. Biocompatibility is also crucial for led to their use in the 3D printing of various bioelectronic
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biomedical applications. devices, including smart electronic clothes, electrodes
for soft sensor systems, wearable heaters, and haptic
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3.1. Metallic materials feedback multimodal sensor devices. Liquid metals are
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Electronic devices benefit greatly from materials with mostly 3D-printed using inkjet printing and DIW, as they
high electrical conductivity. Among the wide range of are not photocurable.
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materials, metals exhibit the highest electrical conductivity.
However, not all metals are suitable for 3D printing due to Metal nanoparticles offer unique properties compared
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their high melting temperatures. Thus, liquid metals and to bulk metals. Their nanoscale size reduces their melting
metal nanoparticles with relatively low melting points are temperature, enabling their use in diverse biomedical
commonly used in 3D printing. 69,70 applications. Highly conductive metal nanoparticles, such
as silver nanoparticles (AgNPs), silver nanowires (AgNWs),
Liquid metals have gained attention owing to their and gold nanoparticles (AuNPs) are commonly used to
flexibility in modification and their high thermal and fabricate bioelectronic devices. 79–83 For example, AgNPs
electrical conductivities. Among various liquid metals, have been employed in the fabrication of optoelectronic
gallium-based alloys, such as eutectic gallium indium devices, 62,84 flexible electrochemical biosensors, and strain
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(EGaIn) and gallium indium tin alloys (Galinstan) are sensors. 86,87 Similarly, AuNPs have been utilized for the
biocompatible, highly conductive, and stable at room biosensing platform that detects COVID-19 antibodies. 88

Figure 2. 3D printing of metallic materials. (A) 3D printing of gallium-based liquid metal via the direct ink writing (DIW) method. Reproduced with
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permission from Wiley. Copyright © 2019 Wiley. (B) 3D-printed gallium-based liquid metal to form electrodes in organic light-emitting diode array.
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Reprinted with permission from AAAS. Copyright © 2022. The Authors, some rights reserved; exclusive licensee AAAS. Distributed under a CC BY-NC
4.0 license (http://creativecommons.org/licenses/by-nc/4.0/). (C) 3D printing of graphene oxide-based ink filaments to construct a graphene aerogel
microlattice with excellent conductivity and light weight. Reproduced with permission from Springer Nature. Copyright © 2015 Nature.
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Volume 10 Issue 6 (2024) 99 doi: 10.36922/ijb.4139