Piezoelectric ceramics are currently of considerable interest for their capabilities of converting compressive/tensile stresses to an electric charge, or vice versa. Because ceramics cannot be cast and machined easily, additive manufacturing (AM) processes (3D printing technology) open an effective pathway in geometrical flexibility. However, the piezoelectric properties limit the application of printed ceramics. This work demonstrates that a piezoelectric-composite slurry with BaTiO 3 nanoparticles (100nm) can be 3D printed using Mask-Image-Projection-based Stereolithography (MIP-SL) technology. After a post-process, the density of 5.64g/cm 3 was obtained, which corresponds to 93.7% of the density of bulk BaTiO 3 (6.02 g/cm 3 ). The printed 1 Zeyu Chen and Xuan Song contribute equally to this paper 2 ceramic exhibits a piezoelectric constant and relative permittivity of 160 pCN -1 and 1350respectively. An ultrasonic transducer with printing focused piezoelectric element was fabricated to realize the energy focusing and ultrasonic sensing. A 6.28MHz ultrasonic scan was achieved by the transducer and successfully visualized the structure of a porcine eyeball.
Bioinspired
hydrogels have promising prospects in applications
such as wearable devices, human health monitoring equipment, and soft
robots due to their multifunctional sensing properties resembling
natural skin. However, the preparation of intelligent hydrogels that
provide feedback on multiple electronic signals simultaneously, such
as human skin receptors, when stimulated by external contact pressure
remains a substantial challenge. In this study, we designed a bioinspired
hydrogel with multiple conductive capabilities by incorporating carbon
nanotubes into a chelate of calcium ions with polyacrylic acid and
sodium alginate. The bioinspired hydrogel consolidates self-healing
ability, stretchability, 3D printability, and multiple conductivities.
It can be fabricated as an integrated strain sensor with simultaneous
piezoresistive and piezocapacitive performances, exhibiting sensitive
(gauge factor of 6.29 in resistance mode and 1.25 kPa–1 in capacitance mode) responses to subtle pressure changes in the
human body, such as finger flexion, knee flexion, and respiration.
Furthermore, the bioinspired strain sensor sensitively and discriminatively
recognizes the signatures written on it. Hence, we expect our ideas
to provide inspiration for studies exploring the use of advanced hydrogels
in multifunctional skin-like smart wearable devices.
A reduction in the particle size is expected to improve the properties and increase the application potential of high-entropy alloys. Therefore, in this study, a novel sol–gel autocombustion technique was first used to synthesize high-entropy alloys. The average grain size of the prepared nanocrystalline CoCrCuNiAl high-entropy alloys showed was 14 nm with an excellent and uniform dispersion, exhibiting a distinct magnetic behavior similar to the superparamagnetic behavior. We show that the metal nitrates first form (Co,Cu,Mg,Ni,Zn)O high-entropy oxides, and then in situ reduce to CoCrCuNiAl high-entropy alloys by the reducing gases, and the chelation between citric acid and the metal ions and the in situ chemical reactions are the dominant reaction mechanisms. We demonstrate that the sol–gel autocombustion process is an efficient way to synthesize solid solution alloys eluding the restriction of a high mixing entropy.
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