A tuning fork gyroscope with drive-sense orthogonal thin-walled holes for high sensitivity.

A tuning fork gyroscope (TFG) with orthogonal thin-walled round holes in the driving and sensing directions is proposed to improve sensitivity. The thin walls formed by through holes produce stress concentration, transforming the small displacement of tuning fork vibration into a large concentrated strain. When piezoelectric excitation or detection is carried out here, the driving vibration displacement and detection output voltage can be increased, thereby improving sensitivity. Besides, quadrature coupling can be suppressed because the orthogonal holes make the optimal excitation and detection positions in different planes. The finite element method is used to verify the benefits of the holes, and the parameters are optimized for better performance. The experimental results show that the sensitivity of the prototype gyroscope with a driving frequency of 890.68 Hz is 100.32 mV/(°/s) under open-loop driving and detection, and the rotation rate can be resolved at least 0.016 (°/s)/Hz, which is about 6.7 times better than that of the conventional TFG. In addition, the quadrature error is reduced by 2.7 times. The gyroscope has a simple structure, high reliability, and effectively improves sensitivity, which is helpful to guide the optimization of piezoelectric gyroscopes and derived MEMS gyroscopes.

Numerical Study of Air Flow Induced by Shock Impact on an Array of Perforated Plates.

This study is focused on the propagation behavior and attenuation characteristics of a planar incident shock wave when propagating through an array of perforated plates. Based on a density-based coupled explicit algorithm, combined with a third-order MUSCL scheme and the Roe averaged flux difference splitting method, the Navier-Stokes equations and the realizable k-ε turbulence model equations describing the air flow are numerically solved. The evolution of the dynamic wave and ring vortex systems is effectively captured and analyzed. The influence of incident shock Mach number, perforated-plate porosity, and plate number on the propagation and attenuation of the shock wave was studied by using pressure- and entropy-based attenuation rates. The results indicate that the reflection, diffraction, transmission, and interference behaviors of the leading shock wave and the superimposed effects due to the trailing secondary shock wave are the main reasons that cause the intensity of the leading shock wave to experience a complex process consisting of attenuation, local enhancement, attenuation, enhancement, and attenuation. The reflected shock interactions with transmitted shock induced ring vortices and jets lead to the deformation and local intensification of the shock wave. The formation of nearly steady jets following the array of perforated plates is attributed to the generation of an oscillation chamber for the inside dynamic wave system between two perforated plates. The vorticity diffusion, merging and splitting of vortex cores dissipate the wave energy. Furthermore, the leading transmitted shock wave attenuates more significantly whereas the reflected shock wave from the first plate of the array attenuates less significantly as the shock Mach number increases. The increase in the porosity weakens the suppression effects on the leading shock wave while increases the attenuation rate of the reflected shock wave. The first perforated plate in the array plays a major role in the attenuation of the shock wave.

High-Throughput, Off-Chip Microdroplet Generator Enabled by a Spinning Conical Frustum.

Although droplet-based microfluidics has been broadly used as a versatile tool in biology, chemistry, and nanotechnology, its rather complicated microfabrication process and the requirement of specialized hardware and operating skills hinder researchers fully unleashing the potential of this powerful platform. Here, we develop an integrated microdroplet generator enabled by a spinning conical frustum for the versatile production of near-monodisperse microdroplets in a high-throughput and off-chip manner. The construction and operation of this generator are simple and straightforward without the need of microfabrication, and we demonstrate that the generator is able to passively and actively control the size of the produced microdroplets. In addition to water microdroplets, this generator can produce microdroplets of liquid metal that would be difficult to produce in conventional microfluidic platforms as liquid metal has high surface tension. Moreover, we demonstrate that this generator can produce solid hydrogel microparticles and fibers using integrated ultraviolet (UV) light. In the end, we further explore the ability of this generator for forming double emulsions by coflowing two immiscible liquids. Given the remarkable abilities demonstrated by this platform and the tremendous potential of microdroplets, this user-friendly method may revolutionize the future of droplet-based chemical synthesis and biological analysis.

The application of a non-doped composite hole transport layer of [MoO3/CBP] n with multi-periodic structure for high power efficiency organic light-emitting diodes.

A non-doped multi-periodic structure of composite hole transport layer of [MoO3/CBP] n was applied to organic light-emitting diodes. All devices with such hole transport layers showed low turn-on voltage of about 3 V, ultra-high luminance of >110 000 cd m-2, high current efficiency of >50 cd A-1, and high EQE of more than 15%. The optimized device exhibited power efficiency increase of 66% and 18% relative to the single periodic and doped structure OLEDs. The achievement of the reduced driving voltage and improved power efficiency can be attributed to the significantly enhanced hole injection and transport induced by the multi-periodic structure of composite hole transport layer, which was demonstrated via a series of hole-only devices. For improved hole injection and transport mechanism, we also provided a detailed discussion in combination with atomic force microscopy measurements.

Rational design of quinoxaline-based bipolar host materials for highly efficient red phosphorescent organic light-emitting diodes.

Two novel bipolar carbazole/diphenylquinoxaline-based host materials 3-(2,3-diphenylquinoxalin-6-yl)-9-phenyl-9H-carbazole (M1) and 3-(4-(2,3-diphenylquinoxalin-6-yl)phenyl)-9-phenyl-9H-carbazole (M2) have been rationally designed and synthesized. The phenyl spacer between the functionalized quinoxaline moiety and the carbazole moiety is also introduced to investigate its influence on their photophysical properties. The chemical structures, and thermal, photophysical and electrochemical properties of the two host materials were characterized and explored in detail. Red phosphorescent light-emitting diodes with M1 and M2 as hosts were prepared to explore their electroluminescent properties. Both M1 and M2 host-based red devices exhibit outstanding electroluminescent performance. For example, two red devices all realize good red emission with the maximum at 594 nm, the maximum external quantum efficiency and luminance can reach 14.66% and 28 619 cd m-2 for M1-based devices and 15.07% and 28 818 cd m-2 for M2-based devices, indicating compounds M1 and M2 designed in this work have potential applications in the development of high-performance monochrome and white OLEDs.