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Materials Science in Additive Manufacturing Functional materials for AM

Table 5. Comparison of materials and fabrication methods for piezoelectrics
3D printing Material Applications Description References
method composition
FDM Cellulose Energy Harvester An all-3D-printed pyro-piezoelectric nanogenerator using cellulose nanocrystals is 115
nanocrystal, and sensors introduced for self-powered cardiorespiratory monitoring, facilitating non-invasive
CNT health tracking.
DIW PVDF, MoS Energy Harvester 3D printing and 2D MoS2 nanofillers enhanced PVDF-based sensors, achieving a 116
2
and sensors piezoelectric coefficient of 48.4 pC N , approximately 8.2 times higher than as-cast
-1
PVDF for advanced precision applications.
DIW P (VDF-TrFE), Sensors A fully printed piezoelectric pressure sensor demonstrated in this work achieves 117
BaTiO a stable output of approximately 2.5 V at 30 kPa over 2000 seconds with minimal
3
variation and is effectively employed in a prosthetic hand to discern the tactile
hardness of various objects.
DLP PZT, SiOC Piezo actuators The described multi-material additive manufacturing technique crafts intricate 3D 118
robotic metamaterials with piezoceramic, metallic, and structural elements, enabling
small-scale devices capable of complex motions and integrated sensing for advanced
robotic and transducer applications.
Abbreviations: CNT: Carbon nanotube; DIW: Direct ink writing; DLP: Digital light processing; FDM: Fused deposition modeling; PZT: Lead zirconate
titanate; PVDF: Polyvinylidene fluoride; SLA: Stereolithography; SLS: Selective laser sintering.

A hybrid thermoelectric-piezoelectric nanogenerator, control. These capabilities underline the significance of the
utilizing cellulose nanocrystals to harvest mechanical inverse piezoelectric effect in various technological fields.
and thermal energy, was fabricated using FDM. This 3D A robotic metamaterial utilizing DLP technology
printing methodology reduces the number of processing has been fabricated, featuring multi-degree-of-freedom
steps required for multilayer fabrication while maintaining movements. This robotic metamaterial is designed as a
excellent stability and performance. The fabricated sensor micro 3D lattice structure that integrates piezoelectric,
exhibits superior mechanical energy harvesting and can conductive, and structural elements. It can undergo
accurately detect heartbeats and respiration regardless numerous deformation modes, including twisting, shear,
of time and location without an external power source. normal deformation, and combinations and amplifications
Furthermore, the device facilitates noninvasive monitoring of these modes. Such robotic metamaterials surpass
of cardiorespiratory status, representing an advancement in the limitations of natural piezoelectric crystals and are
the development of human-machine interfaces through its expected to directly influence the development of future
self-powered operation (Figure 5B). Sensors fabricated micro-robots and transducers. 118
115
using DIW with MoS -enhanced PVDF demonstrated 3D printing of piezoelectric materials allows for the
2
a piezoelectric coefficient (d ) of 48.4 pC N , which is precise fabrication of complex shapes and structures,
−1
33
approximately eight times higher than that of sensors applicable in various fields such as energy harvesters
116
produced through casting. In addition, a fully printed and and sensors. This technology enables the design of
PDMS-packaged piezoelectric sensor using P(VDF-TrFE)- multifunctional sensors with integrated capabilities. In
BaTiO was fabricated through DIW. The fabricated sensor addition, 3D printing facilitates the structural optimization
3
was successfully attached to a prosthetic hand, enabling it to of lightweight actuators. However, products manufactured
detect dynamic tactile data and identify objects. 117 through this method may have reduced durability compared
3.4.2. Piezo actuators to those produced by traditional methods, and minor
defects that occur during the printing process can lead to
The inverse piezoelectric effect converts external electrical performance degradation. Consequently, further research
signals into mechanical energy, leading to the physical and development are needed to enhance the piezoelectric
deformation of piezoelectric materials. When voltage is efficiency and durability of these materials, addressing the
applied, the material’s crystal structure deforms, slightly challenges inherent in the 3D printing process to ensure
changing its dimensions. The extent of this expansion or reliable and robust performance in practical applications.
contraction is influenced by the magnitude and direction
of the applied voltage and the type of material. This precise 3.5. Thermoelectrics
control over deformation is utilized in applications such Thermoelectrics directly transform the temperature
as precision positioning, vibration generation, and fluid difference into electric current and vice versa using the

Volume 3 Issue 2 (2024) 14 doi: 10.36922/msam.3323