Simulation and Experiment on Droplet Volume for the Needle-Type Piezoelectric Jetting Dispenser

The needle-type piezoelectric jetting dispenser is widely applied in the microelectronics packaging field, and it is important to control the droplet size to ensure that the droplet jetting process is successful. In this study, we analyzed the influences of system parameters, such as air pressure, nozzle size, needle strokes, and liquid properties, on droplet size and morphology by considering the droplet formation and separation process through a numerical simulation. An experimental platform was also designed to verify the reliability of the simulations and further analyze strategies for controlling the droplet size. We found that the droplet volume can be increased with an increase in air pressure, needle strokes, and nozzle size until the flow-stream or satellite droplets appear. On the other hand, very small values of these parameters will lead to adhesion or micro-dots. A large nozzle and needle displacement should be chosen for the high-viscosity liquid in order to produce normal droplets. The results also show the recommended ranges of parameter values and suitable droplet volumes for liquids with different viscosities, and these findings can be used to guide the droplet volume control process for needle-type jetting dispensers

Simulation and Experiment on Droplet Formation and Separation for Needle-Type Micro-Liquid Jetting Dispenser

The needle-type droplet jetting dispenser has wide applications in the field of microelectronic packaging, and for which the good quality of droplet formation and separation is the key to successful dispensing. This paper simulates the droplet jetting process which has been divided into 5 stages named backflow, growth, droplet extension, breakage, and separation, and analyses the combined effects of system parameters, such as pressure, viscosity, needle stroke, and nozzle diameter, on the changes of morphologies of ejected droplets, which is verified by experiments. The simulation and experiment results show that a higher driving pressure is quite suitable for the high-viscosity liquid to form normal droplets by avoiding adhesion. When increasing the needle stroke, the pressure should also be lowered properly to prevent the flow-stream. Besides, the nozzle with a large diameter is much more likely to cause sputtering or satellite-droplet problems. The results have a great significance for guiding the parameter settings of the needle-type dispensing approach

The microstructure and ferroelectric property of Nd-doped multiferroic ceramics Bi0.85Nd0.15FeO3

The microstructures of Bi0.85Nd0.15FeO3 ceramics were investigated by using transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), convergent-beam electron diffraction (CBED) and X-ray energy dispersive spectrometry (EDS). The superstructure phase related to 1/4(hh0)(p) and 1/4(00 l)(p) diffraction spots were observed in the samples. It is found that the superstructure phase can co-exist with R3c phase in a single grain. The bright and dark field images accompanied with SAED patterns provided evidences of the superstructure phase dispersed into the matrix with R3c symmetry and evolution of the domain. The ferroelectric domain wall was observed according to the displacement of Fe3+ ions respect to Bi3+ sub-lattice in the ferroelectric R3c phase based on HRTEM observations. The space group Pnam of the superstructure was identified by combining SAED and CBED techniques. EDS measurement revealed that the concentration of Nd in the Pnam phase is higher than that in R3c phase. This might mean that the transition from R3c to Pnam structure is due to the inhomogeneous distribution of the Nd concentration and the weakened stereochemical activity of Bi3+ lone electron pair, arisen from the increase in Nd content. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved

Flexible Wearable Pressure Sensor Based on Collagen Fiber Material

Flexible wearable pressure sensors play a pivotal role in healthcare monitoring, disease prevention, and humanmachine interactions. However, their narrow sensing ranges, low detection sensitivities, slow responses, and complex preparation processes restrict their application in smart wearable devices. Herein, a capacitive pressure sensor with high sensitivity and flexibility that uses an ionic collagen fiber material as the dielectric layer is proposed. The sensor exhibits a high sensitivity (5.24 kPa−1), fast response time (40 ms), long-term stability, and excellent repeatability over 3000 cycles. Because the sensor is resizable, flexible, and has a simple preparation process, it can be flexibly attached to clothes and the human body for wearable monitoring. Furthermore, the practicality of the sensor is proven by attaching it to different measurement positions on the human body to monitor the activity signal

Fabrication of wafer-scale nanoporous AlGaN-based deep ultraviolet distributed Bragg reflectors via one-step selective wet etching

Abstract In this paper, we reported on wafer-scale nanoporous (NP) AlGaN-based deep ultraviolet (DUV) distributed Bragg reflectors (DBRs) with 95% reflectivity at 280 nm, using epitaxial periodically stacked n-Al0.62Ga0.38N/u-Al0.62Ga0.38N structures grown on AlN/sapphire templates via metal–organic chemical vapor deposition (MOCVD). The DBRs were fabricated by a simple one-step selective wet etching in heated KOH aqueous solution. To study the influence of the temperature of KOH electrolyte on the nanopores formation, the amount of charge consumed during etching process was counted, and the surface and cross-sectional morphology of DBRs were characterized by Scanning electron microscopy (SEM) and atomic force microscopy (AFM). As the electrolyte temperature increased, the nanopores became larger while the amount of charge reduced, which revealed that the etching process was a combination of electrochemical and chemical etching. The triangular nanopores and hexagonal pits further confirmed the chemical etching processes. Our work demonstrated a simple wet etching to fabricate high reflective DBRs, which would be useful for AlGaN based DUV devices with microcavity structures

Parkinson’s disease-associated ATP13A2/PARK9 functions as a lysosomal H+,K+-ATPase

Abstract Mutations in the human ATP13A2 (PARK9), a lysosomal ATPase, cause Kufor-Rakeb Syndrome, an early-onset form of Parkinson’s disease (PD). Here, we demonstrate that ATP13A2 functions as a lysosomal H+,K+-ATPase. The K+-dependent ATPase activity and the lysosomal K+-transport activity of ATP13A2 are inhibited by an inhibitor of sarco/endoplasmic reticulum Ca2+-ATPase, thapsigargin, and K+-competitive inhibitors of gastric H+,K+-ATPase, such as vonoprazan and SCH28080. Interestingly, these H+,K+-ATPase inhibitors cause lysosomal alkalinization and α-synuclein accumulation, which are pathological hallmarks of PD. Furthermore, PD-associated mutants of ATP13A2 show abnormal expression and function. Our results suggest that the H+/K+-transporting function of ATP13A2 contributes to acidification and α-synuclein degradation in lysosomes

Supplementary document for Low threshold AlGaN-based deep ultraviolet laser enabled by nanoporous cladding layer - 6799781.pdf

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