Characterization and verification of astigmatic interferometric particle imaging for volumetric droplet 3D position and size measurement

Sprays generated by atomization processes have been used in a wide range of fields. The size and spatial distribution of volumetric droplets in a spray are critical parameters in industrial applications. Astigmatic interferometric particle imaging (AIPI), an extension of the traditional interferometric particle imaging (IPI), is developed to simultaneously measure the size and 3D position of volumetric droplets in a sparse spray. Based on the generalized Huygens–Fresnel integral and the transfer matrix, the size and depth position of droplet can be respectively extracted from the fringe spacing and orientation of interferogram in AIPI. An AIPI setup is established to characterize droplets in a sparse spray generated by a nozzle with the AIPI calibration procedure adopted. The measured parameters by AIPI are compared with those obtained synchronously by digital inline holography, which is regarded as a standard measurement technique. Results show that the average deviation values of droplet size and depth position are respectively 3.8% and 6.8%. AIPI has been demonstrated with high accuracy in simultaneous 3D positions and size measurements.     

Hydrogel Microcapsules with a Thin Oil Layer: Smart Triggered Release via Diverse Stimuli

A hydrogel microcapsule with an intermediate thin oil layer is presented to achieve smart release of a broad range of cargoes triggered via diverse stimuli. A microfluidic technique is used to produce triple emulsion droplets with a thin oil layer that separates the innermost aqueous phase from the hydrogel prepolymer phase, which transforms into a hydrogel shell via photopolymerization. The intermediate oil layer within the hydrogel microcapsule acts as an effective diffusion barrier, allowing encapsulation of various small cargoes within a porous hydrogel shell until a stimulus is applied to destabilize the oil layer. It is demonstrated that diverse stimuli including chemical dissolution, mechanical stress, and osmotic pressure can be utilized to release the encapsulated cargo on-demand. In addition, osmotic pressure and the hydrogel shell thickness can be independently tuned to control the onset time of release as well as the release behavior of multi-cargo encapsulated hydrogel microcapsule. The release can be either simultaneous or selective.     

基于类水滴状微结构的微通道流动和散热性能研究

为了有效提高微通道散热器的散热性能,设计了 一种含有类水滴状微结构的微通道散热器,并采用仿真模拟方法研究了微通道内类水滴状微结构的数量和高度变化对微通道的压力损失和散热性能的影响.在热流密度为100 W/cm2,入口端流体速度为1 m/s的条件下,设计了 9组不同的含类水滴状微结构微通道.其中的5组通过改变单条微通道内类水滴状微结构的数量进行研究,得出当微结构数量为7时微通道的综合散热性能最优,其微通道底面平均温度下降了 18.42 K,散热系数提高了 37.63％.同时在微结构数量为7的基础上再次设计4组微通道,研究了微结构的高度对微通道散热性能的影响,得出当各微结构的高度沿流体流动方向逐次增高时,散热系数几乎不变,压力损失降低了 11.93％.     

催化裂化沉降器内液滴运动规律的数值模拟研究

催化裂化沉降器结焦将导致非计划停工,严重影响催化裂化装置的长周期运行.首先求取了单位时间沉降器内冷凝的油浆液滴的质量,然后利用颗粒轨道模型对液滴的运动轨迹进行模拟计算,得到液滴的停留时间、运动轨迹和分布区域.模拟计算结果表明,液滴在沉降器内的运动具有很强的随机性,不同大小的油浆液滴的停留时间不同,但大部分的液滴粘附在沉降器内壁和旋风分离器外壁上,进而缩合结焦.加强沉降器的保温可减少油气重组分的冷凝,采用"高温汽提"和"化学汽提"可减少进入沉降器的油气重组分的量,从而减少沉降器结焦.     

利用电子加速器对涤纶进行接枝改性

针对涤纶具有熔融可燃性、易引发火灾的问题,利用电子加速器对涤纶进行辐射接枝改性,研究不同辐射剂量和单体(甲基丙烯酸、丙烯酸、丙烯酰胺)对接枝率的影响,并对接枝后纤维的性能进行分析.结果表明:辐照剂量和单体浓度的适度增加可导致接枝率的升高;接枝后样品无熔滴现象,即其阻燃性能得到了改善.     

Experimental research of drop‐on‐demand droplet jetting 3D printing with molten polymer

Three‐dimensional (3D) printing technology has become an effective method for parts manufacturing and got a certain application in many fields. Now, drop‐on‐demand droplet jetting 3D printing appears as a new method of manufacturing technology which has a proven research progress for metal, colloid, and liquid resin materials. However, there are hardly any researches of droplet jetting 3D printing with molten polymer. So, considering molten polymer as the jetting material with droplet jetting method is an explorative direction. In order to attain the molten polymer droplets and achieve droplet jetting 3D printing with molten polymer, the 3D printing technology of differential melt (3DPDM) is developed independently. According to 3DPDM, a complete set of drop‐on‐demand droplet jetting 3D printer have been developed. In this work, PP (6820) was chosen as the experimental material. Under the different print parameters such as the rotation speed of screw, nozzle diameter, mechanical impact frequency, heating temperature, the space between nozzle and platform, the form, and deposition of droplets were studied. Furthermore, the optimal print parameters were summarized. By printing models with the optimal print parameters, it turned out that the 3DPDM is able to achieve drop‐on‐demand droplet jetting 3D printing with molten polymer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45933.     

On the steady‐state drop size distribution in stirred vessels. Part I: Effect of dispersed phase viscosity

Previous studies on emulsification have used the maximum drop size (d_max) or Sauter mean diameter ( ) to investigate the effect of viscosity on the drop size distribution (DSD), however, these parameters fall short for highly polydispersed emulsions. In this investigation (Part I), the steady‐state DSD of dilute emulsions is studied using of silicon oils with viscosities varying across six orders of magnitude at different stirring speeds. Different emulsification regimes were identified; our modeling and analysis is centered on the intermediate viscosity range where interfacial cohesive stresses can be considered negligible and drop size increases with viscosity. The bimodal frequency distributions by volume were well described using two log‐normal density functions. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3293–3302, 2018     

Hydrodynamically Guided Hierarchical Self‐Assembly of Peptide–Protein Bioinks

Effective integration of molecular self‐assembly and additive manufacturing would provide a technological leap in bioprinting. This article reports on a biofabrication system based on the hydrodynamically guided co‐assembly of peptide amphiphiles (PAs) with naturally occurring biomolecules and proteins to generate hierarchical constructs with tuneable molecular composition and structural control. The system takes advantage of droplet‐on‐demand inkjet printing to exploit interfacial fluid forces and guide molecular self‐assembly into aligned or disordered nanofibers, hydrogel structures of different geometries and sizes, surface topographies, and higher‐ordered constructs bound by molecular diffusion. PAs are designed to co‐assemble during printing in cell diluent conditions with a range of extracellular matrix (ECM) proteins and biomolecules including fibronectin, collagen, keratin, elastin‐like proteins, and hyaluronic acid. Using combinations of these molecules, NIH‐3T3 and adipose derived stem cells are bioprinted within complex structures while exhibiting high cell viability (>88%). By integrating self‐assembly with 3D‐bioprinting, the study introduces a novel biofabrication platform capable of encapsulating and spatially distributing multiple cell types within tuneable pericellular environments. In this way, the work demonstrates the potential of the approach to generate complex bioactive scaffolds for applications such as tissue engineering, in vitro models, and drug screening.     

Formation process of core‐shell microparticles by solute migration during drying of homogenous composite droplets

Particle formation process during spray drying profoundly impacts particle morphology and microstructure. This study experimentally investigated the formation of core‐shell‐structured microparticles by one‐step drying of composite droplets made of Eudragit^® RS (a polycationic acrylic polymer in nanoparticle form) and silica sol. The formation of an incipient surface shell was monitored using single droplet drying technique, and the freshly formed shell was recovered for subsequent analyses. Adding silica to RS precursor increased the shell formation time and altered the properties of the incipient shell from water‐dispersible to nondispersible. The incipient shell formed from RS/silica droplets with mass ratios of 1.5%:1.5% and 0.5%:2.5% showed ingredient segregation with a preferential accumulation of RS, similar to the shell region of dried microparticles. After shell formation, excess silica sol in the liquid phase could flow inward, producing a dense core. This mobility‐governed solute migration would be useful for constructing core‐shell microparticles using other precursor systems. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3297–3310, 2017