In the field of soft electronics, high-resolution and transparent structures based on various flexible materials constructed via various printing techniques are gaining attention. With the support of electrical stress-induced conductive inks, the electrohydrodynamic (EHD) jet printing technique enables us to build high-resolution structures compared with conventional inkjet printing techniques. Here, EHD jet printing was used to fabricate a high-resolution, transparent, and flexible strain sensor using a polydimethylsiloxane (PDMS)/xylene elastomer, where repetitive and controllable high-resolution printed mesh structures were obtained. The parametric effects of voltage, flow rate, nozzle distance from the substrate, and speed were experimentally investigated to achieve a high-resolution (5 µm) printed mesh structure. Plasma treatment was performed to enhance the adhesion between the AgNWs and the elastomer structure. The plasma-treated functional structure exhibited stable and long strain-sensing cycles during stretching and bending. This simple printing technique resulted in high-resolution, transparent, flexible, and stable strain sensing. The gauge factor of the strain sensor was significantly increased, owing to the high resolution and sensitivity of the printed mesh structures, demonstrating that EHD technology can be applied to high-resolution microchannels, 3D printing, and electronic devices.
The
use of metal halide perovskite nanocrystals in display applications
has garnered attention owing to their excellent optoelectronic properties,
such as high color purity with an extremely narrow full width at half
maximum and high photoluminescence quantum yield. Because metal halide
perovskite nanocrystals, which are synthesized from precursor solutions,
exhibit high crystallinity, research on high-resolution patterning
has become popular owing to its cost-effectiveness and convenience
for large-area processing. Various solution-based fabrication techniques,
including lithographic approaches, electrospinning methods, and inkjet
printing, have been employed to realize perovskite micropatterns for
display applications. However, achieving high-resolution, transparent,
and stable micropatterns in a time- and cost-effective manner remains
challenging. Herein, we propose a cost-effective one-step electrohydrodynamic
(EHD) jet-printing process for high-resolution, transparent, flexible,
and stable methylammonium lead bromide/polyacrylonitrile (MAPbBr3/PAN) composite patterns and its surface nanomorphology control.
We optimized the printing ink and processing conditions to not only
generate a stable EHD jet but also ensure excellent optoelectronic
properties of the MAPbBr3/PAN composite patterns. We parametrically
observed its surface nanomorphology change from a nanoporous structure
to a dense flat surface with the fabrication temperature. The MAPbBr3/PAN composite patterns fabricated under optimum conditions
showed a high resolution of approximately 10 μm with high crystallinity,
a high transmittance above 95% at visible wavelengths, and high stability
under water for more than 20 days. The stability against water was
attributed to the dense morphology formed at a processing temperature
of 80 °C. In addition, the MAPbBr3/PAN composite patterns
withstood 30,000 bending cycles with a 2 mm bending radius and 2%
strain without a decrease in the photoluminescence intensity. The
proposed EHD printing technique may open up intriguing possibilities
for the fabrication of water-stable, transparent, and flexible display
applications using metal halide perovskite nanocrystals.
For effective ocean energy harvesting, it is necessary to understand the coupled motion of the piezoelectric nanogenerator (PENG) and ocean currents. Herein, we experimentally investigate power performance of the PENG in the perspective of the fluid–structure interaction considering ocean conditions with the Reynolds number (Re) values ranging from 1 to 141,489. A piezoelectric polyvinylidene fluoride micromesh was constructed via electrohydrodynamic (EHD) jet printing technique to produce the β-phase dominantly that is desirable for powering performance. Water channel was set to generate water flow to vibrate the flexible PENG. By plotting the Re values as a function of nondimensional bending rigidity (KB) and the structure-to-fluid mass ratio (M*), we could find neutral curves dividing the stable and flapping regimes. Analyzing the flow velocities between the vortex and surroundings via a particle image velocimetry, the larger displacement of the PENG in the chaotic flapping regime than that in the flapping regime was attributed to the sharp pressure gradient. By correlating M*, Re, KB, and the PENG performance, we conclude that there is critical KB that generate chaotic flapping motion for effective powering. We believe this study contributes to the establishment of a design methodology for the flexible PENG harvesting of ocean currents.
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