The photopolymerized acrylate products, fabricated using piezoelectric inkjet three dimensional printers, can be deformed under some printing process conditions. To understand and solve this deformation problem, we focus on the drop dynamics of the acrylate resin ink before being cured by the ultraviolet light. We numerically solve the full Navier-Stokes equation with the Volume-of-fluid (VOF) method to investigate the impact, spreading, and recoiling behavior of the resin ink droplet to show how the resin ink flow characteristics result in the shape change of the products. We have successfully developed the numerical models for the analysis of the drop dynamics of the resin ink in piezoelectric inkjet three dimensional printers.
In this paper, newly designed magnetized inductively coupled plasma ion beam etcher (M-ICP IBE) is proposed. Plasma density and electron temperature were measured with respect to the magnetic flux density and to the source power. In addition, ion energy distribution and ion flux, the result of which were correlated with plasma density and electron temperature characteristics, were measured. The relationship among plasma density, electron temperature, and the diameter of a screen grid hole were also studied in order to extract optimized ion beam from the grid layer. Besides, the ion beam characteristics with respect to the screen grid voltage and to the acceleration grid voltage were investigated. Meanwhile, the dry etching characteristics of SiO2 in ICP IBE and that of M-ICP IBE were investigated. It was confirmed that the beam extracted from the grid layer in M-ICP IBE showed high ion flux even at low ion energy, where ICP IBE showed much lower ion flux. As a result, the etch rate of SiO2 in M-ICP IBE was about seven times higher than that in ICP IBE.
Abstract Engineering the coupling behavior between a functional thin film and a soft substrate provides an attractive pathway for controlling various properties of thin‐film materials. However, existing studies mostly rely on uniform deformation of the substrate, and the effect of well‐regulated and nonuniform strain distributions on strain‐sensitive thin‐film responses still remains elusive. Herein, artificially strain‐regulated elastic media are presented as a novel platform for tailoring strain‐sensitive thin‐film responses. The proposed artificial soft elastic media are composed of embedded arrays of inkjet‐printed polymeric strain modulators that exhibit a high modulus contrast with respect to that of the soft matrix. This strain‐modulating lattice induces spatially regulated strain distributions based on localized strain‐coupling. Controlling the structural parameters and lattice configurations of the media leads to spatial modulation of the microscopically localized as well as macroscopically accumulated strain profiles. Uniform thin films coupled to these media undergo artificially tailored deformation through lattice‐like strain‐coupled pathways. The resulting phenomena yield programmable strain‐sensitive responses such as spatial arrangement of ternary‐state surface wrinkles and stepwise tuning of piezoresistive responses. This work will open a new avenue for addressing the issue of controlling strain‐sensitive thin‐film properties through structural engineering of artificial soft elastic media.
A fiber-based single-walled carbon nanotube (SWCNT) thin-film-transistor (TFT) has been proposed. We designed complementary SWCNT TFT circuit based on SPICE simulations, with device parameters extracted from the fabricated fiber-based SWCNT TFTs, such as threshold voltage, contact resistance, and off-/gate-leakage current. We fabricated the SWCNTs CMOS inverter circuits using the selective passivation and n-doping processes on a fiber substrate. By comparing the simulation and experimental results, we could enhance the circuit's performance by tuning the threshold voltage between p-type and n-type TFTs, reducing the source/drain contact resistance and off current level, and maintaining a low output capacitance of the TFTs. Importantly, it was found that the voltage gain, output swing range, and frequency response of the fiber-based inverter circuits can be dramatically improved.
Elastomeric mirror is one of the main components of systems that require tunable optical characteristics, and is being applied in various devices such as optical zoom camera, electrostatic actuator, and augmented/virtual reality (AR/VR) display. Generally, to fabricate an elastomeric mirror, a metal layer is deposited on an elastomer substrate by vacuum process such as thermal evaporation, e-beam evaporation, and sputtering. However, these processes can damage the elastomeric substrate, thereby degrading the quality of the mirror surface. The metal layer formed on the elastomeric substrate is also vulnerable to small deformation, which limits applications of elastomeric mirror. In this work, we report all-solution-processed elastomeric mirror film whose constituent layers were deposited sequentially by spin coating and dip coating method. The film consists of polydimethylsiloxane (PDMS) base, aluminum (Al) mirror, and PDMS encapsulation layer. As a material of mirror layer, we selected a 'mirror ink', which composed of Al powder, organic solvent, adhesive and mainly used for screen printing. We adjusted the dilution concentration of mirror ink to make it suitable for the solution process and controlling the roughness of the coated mirror layer. In addition, there was no damage to the mirror layer against deformation due to the presence of encapsulation layer, so it can be attachable well to the curved surface. As an example of application, we demonstrated a seamless display system by placing the elastomeric mirror between two curved panels. We expect that our elastomeric mirror will be applicable to various tunable optical systems.
We have developed an approach to fabricate pixelated organic polymer light-emitting devices (OPLED) using an imprinting technique. The pixel array pattern was first defined in an insulating polymer layer on indium tin oxide glass by direct imprinting, followed by the spin-coating of OPLED polymers and cathode metal deposition. We demonstrated successful fabrication and operation of OPLED pixels of sizes from 50 μm down to 2 μm. Optoelectronic characterization is performed on these devices, and measured results show comparable device performance with OPLED pixels patterned by other methods. This fabrication scheme holds many merits such as easy to process, low-cost, high yield, expandable to flexible substrate, capable of repeated imprinting for large area arrays, and the potential to pattern submicron and nanoscale organic polymer light emitters.
This article is a study on the center frequency reconfiguration of a flexible antenna. In the case of a flexible antenna, the center frequency shifts due to parasitic components generated when the antenna is bent. In previous studies, research has been conducted to reconfigure the center frequency through a reconfiguration circuit. When using a reconfiguration circuit, it is difficult to flexibly configure all systems due to increased complexity. Therefore, in this article, we propose a flexible antenna that does not change the center frequency even when the antenna is bent through a wavy surface structure without the aid of a frequency reconfiguration circuit. By studying the parasitic component that occurs when the antenna is bent, the cause of the change in the center frequency is identified, and a structure to solve it is proposed. In order to calculate the parasitic component, an approximate model divided by the vertical component of the bending surface of the flexible antenna was used. In this article, a gating air-gap structure was proposed to realize a wavy surface, and through this, the antenna gain was increased by 1.47 dBi. In addition, through the wavy surface structure using E-textile, it was possible to reduce the frequency shift by about 86% (70–10 MHz) and improve the gain reduction by about 86% (4.4–0.63 dBi). This allows the frequency to be reconfigured in real time without additional circuitry.
Abstract A new estimation method for image sticking has been developed that can effectively eliminate the influence by the difference in long‐range non‐uniformity pattern. An 8×8 chessboard pattern was used for selective degradation, and normalization based on extracted reference and coefficient of variation were adopted for better results.
On page 3094, Y. Hong and co-workers develop a key enabling technology for stretchable displays sustaining their original pixel resolution even when stretched by using ferromagnetic conductive nickel composite electrodes and a hidden pixel structure. The hidden pixels connected via the composite electrodes are turned on under the tensile strain, thus sustaining the original pixel resolution due to the negatively strain-dependent electrical resistance of the composite electrode.
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