Electrochemical discharge machining (ECDM) is a spark-based micromachining method especially suitable for the fabrication of various microstructures on nonconductive materials, such as glass and some engineering ceramics. However, since the spark discharge frequency is drastically reduced as the machining depth increases ECDM microhole drilling has confronted difficulty in achieving uniform geometry for machined holes. One of the primary reasons for this is the difficulty of sustaining an adequate electrolyte flow in the narrow gap between the tool and the workpiece, which results in a widened taper at the hole entrance, as well as a significant reduction of the machining depth. In this paper, ultrasonic electrolyte vibration was used to enhance the machining depth of the ECDM drilling process by assuring an adequate electrolyte flow, thus helping to maintain consistent spark generation. Moreover, the stability of the gas film formation, as well as the surface quality of the hole entrance, was improved with the aid of a side-insulated electrode and a pulse-power generator. The side-insulated electrode prevented stray electrolysis and concentrated the spark discharge at the tool tip, while the pulse voltage reduced thermal damage to the workpiece surface by introducing a periodic pulse-off time. Microholes were fabricated in order to investigate the effects of ultrasonic assistance on the overcut and machining depth of the holes. The experimental results demonstrated that the possibility of consistent spark generation and the machinability of microholes were simultaneously enhanced.
We present a novel technique for realizing an electrical circuit composed of organic devices on a highly flexible, stretchable, and patchable freestanding substrate, using a photo-curable polyurethaneacrylate (PUA) mixture. Substrate structure was designed under consideration of enhanced mechanical strength in addition to flexibility, stretchability, and adhesive properties. The designed components facilitate the fabrication of highly flexible and stretchable electrodes without additional photolithography or patterning processes, and the fabricated organic circuits are substantially free from structural stress and strain induced from the substrate deformation. High flexibility and adhesive properties also enable mounting of the organic circuits onto nonflat surfaces with conformal contact. In addition, high light transmissivity of PUA suggests strong potential for a wide range of optoelectronic applications. We anticipate that these results will be applied to the development of various flexible, stretchable, and patchable organic devices, which can lead to further applications in many fields of science and engineering.
Real‐time active control of the handedness of circularly polarized light emission requires sophisticated manufacturing and structural reconfigurations of inorganic optical components that can rarely be achieved in traditional passive optical structures. Here, robust and flexible emissive optically‐doped biophotonic materials that facilitate the dynamic optical activity are reported. These optically active bio‐enabled materials with a chiral nematic‐like organization of cellulose nanocrystals with intercalated organic dye generated strong circularly polarized photoluminescence with a high asymmetric factor. Reversible phase‐shifting of the photochromic molecules intercalated into chiral nematic organization enables alternating circularly polarized light emission with on‐demand handedness. Real‐time alternating handedness can be triggered by either remote light illumination or changes in the acidic environment. This unique dynamic chiro‐optical behavior presents an efficient way to design emissive bio‐derived materials for dynamic programmable active photonic materials for optical communication, optical coding, visual protection, and visual adaptation.
We report a mesogenic
compound which introduces nematic liquid
crystal (LC) ordering into the benzothienobenzothiophene (BTBT) family
of LCs, creating a new class of LC semiconducting materials which
respond in a facile way to anisotropic surfaces, and can, thereby,
be effectively processed into highly oriented monodomains. Measurement
on these domains of the electrical conductivity, with in situ monitoring
of domain quality and orientation using LC birefringence textures
in electroded cells, brings a new era of precision and reliability
to the determination of anisotropic carrier mobility in LC semiconductors.
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