Page 22 - MSAM-3-2

Materials Science in Additive Manufacturing Functional materials for AM

of 10 nW and 8.3 mV, respectively, after a thousand bending atoms, carbon nanotubes (CNTs) with a cylindrical
cycles at 35 K. Figure 6B illustrates the manufacturing structure, and fullerenes with a spherical shape. These
124
process and the complete structure of the flexible TEG. This materials find wide applications in various fields, such
research indicates the potential for printing TEGs on paper, as microelectronics, electrochemical biosensors, strain
which is widely used in various industries, thus enhancing sensors, and chemical sensors. 131,132 At present, the general
the scalability of TEGs. Furthermore, Mytafides et al. manufacturing methods for carbon-based materials are
130
fabricated TEGs using ink dispensing with single-walled chemical vapor deposition (CVD) and arc discharge.
carbon nanotube (SWCNT) material. The resulting TEGs However, CVD has disadvantages, such as the use of
achieved high flexibility and PF values of 308 μW/m·K and numerous solvents, complex manufacturing processes,
-2
258 μW/m·K for the p-type and n-type film, respectively. and high costs. The arc discharge method may also
-2
The materials used were SWCNTs/sodium dodecylbenzene be susceptible to impurities and material wastage.
133
sulfonate and SWCNTs/cetyltrimethylammonium bromide. Therefore, various printing techniques such as DIW, binder
These TEGs maintained stability even in encapsulated jetting, inkjet printing, spray coating, FDM, and SLS have
conditions, demonstrating the potential for advancing been developed to address these problems. These methods
TEG technology by adopting new materials and producing offer advantages such as simplification of processes,
durable TEGs for applications in extreme conditions. precise structure printing, minimal material wastage, and
Figure 6A depicts the structural composition, flexibility, and rapid prototyping. However, challenges remain, including
overall construction of the fabricated TEGs. high porosity, weak connections between layers, and
ensuring the production of high-quality materials.
134
3.6. Carbon-based materials Recent advances in 3D printing technology for carbon-
Carbon-based materials are compounds consisting of based materials are summarized in Table 7, with improved
carbon atoms, with properties varying according to their performance and applications in sensor and battery.
chemical structure. They generally exhibit lightweight,
high strength, electrical and thermal conductivity, and 3.6.1. Carbon-based sensors
chemical stability. Examples of carbon-based materials Carbon-based chemical and strain sensors have
include graphene, which consists of widely spread carbon revolutionized modern sensing technology. Chemical

A B

Figure 6. Applications of thermoelectric materials. (A) Fabrication of an all-carbon, fully printed, and flexible thermoelectric generator, including
its structure, flexibility, and overall composition. Images reproduced with permission from Mytafides et al. Copyright 2021 © American Chemical
130
Society. (B) Schematic diagram illustrating the fabrication process and the resulting transparent paper-based flexible thermoelectric generator. Images
reproduced with permission from Zhao et al. Copyright © 2019 American Chemical Society. Abbreviations: OTEG: Organic thermoelectric generator;
124
PTFE: Polytetrafluoroethylene; TE: Thermoelectric.
Volume 3 Issue 2 (2024) 16 doi: 10.36922/msam.3323