激光全息干涉测定微通道内气液传质

为了进一步理解微通道内气液两相传质过程机理,利用激光全息干涉条纹与流体折射率以及折射率与流体浓度的关系,采用激光显微全息干涉测试系统对微通道入口处Taylor气泡形成过程中的液相侧浓度分布进行了测定。微通道尺寸为深100μm,宽2000μm,长4cm。气相采用CO2,液相使用无水乙醇。利用图像采集系统对干涉条纹的变化过程进行实时记录,并利用自编图像处理软件对干涉条纹图像进行处理,得到了Taylor气泡形成过程中液相侧浓度分布和近界面浓度边界层厚度。结果表明,在Taylor气泡形成过程中有较强的传质发生,液相近界面浓度和浓度边界层厚度均随着气液相流速的增大而减小。结果显示,利用激光显微全息干涉测试系统,对微观尺度通道内部的气液传质过程进行实时测定研究,可得到清晰的图像和满意的结果。     

碱性抛光液中氧化剂的钝化作用对碟形坑的影响

摘要：本文研究了碱性精抛液的电化学行为。主要研究内容为不同H2O2浓度电解液中腐蚀电位（Ecorr）和腐蚀电流（Icorr）的变化规律,对比了不同精抛电解液的极化曲线,分析了H2O2的钝化作用对控制碟形坑的影响。结果表明：在电化学实验过程中,随着H2O2浓度的增加,腐蚀电位逐渐增加然后趋于平缓,相反腐蚀电流逐渐减小。同时,精抛后的碟形坑随着H2O2浓度的增加而减小,平坦化效果得到了优化。     

KLQ—1型快速冷冻器的研制及应用

在冰冻断裂复型技术中,为了保持活组织的生活状态,把人工损伤减小到最低程度,Heuser at al首先用液氦做冷却剂,冷却金属至-268.9℃,然后把活组织样品与低温金属块接触,以达到10~4K/秒的快速冷冻速度,用该法冷冻的材料进行复型,获得了15微米玻璃化冷冻深度的复型面,山田英智等改进了Van Harreveld at al的仪器,首先用液氮冷却金属块,用上述方法亦获得了复型。该法制得的复型面虽比Heuser的方法狭窄,但液氮便宜又容易获得,所以此法值得推广。为什么上述学者不用液体浸渍法而用与低温金属相接触的方法冷冻样品呢?这是由于本方法样品冷冻的速率快,可高于10~4K/秒以上。而液氮或液体氟里昂浸渍法最多只可达2.5×10~3K/秒的冻结速率,不易使细胞质迅速玻璃化。快速冻结法就是基于上述原理而设计的。     

表面活性剂在纳米材料合成中的应用

阐述了表面活性剂分散机制及在纳米材料制备中的分散作用,介绍了以表面活性剂为基础的各种纳米材料制备方法的机理:如以表面活性剂形成的各种有序聚集体为模板的模板法、用表面活性剂稳定形成的微乳液为介质的微乳法、水热法、溶胶-凝胶法等。重点总结了表面活性剂在不同方法制备纳米材料中的最新性、前沿性的研究成果,并展望了表面活性剂在该领域中的应用前景。     

改良二甲基亚砜冷冻割断法的效果观察

二甲基亚砜冷冻割断技术是一种制作扫描电子显微镜样品，可观察组织细胞内部结构的方法。是利用一种特殊的自制液氮冷冻割断装置，把二甲基亚砜溶液滴成珠状，将固定好的样品放人液珠中，由于液氮的冷冻作用，使二甲基亚砜很快包裹着样品由液态变为固态，用器具将冰珠快速割断，以暴露出样品断面。     

科技市场与咨询服务

光纤内窥镜液氮冷冻诊治仪随着低温外科学的发展,冷冻疗法已在皮肤科、妇科、眼科、耳鼻喉科、肿瘤科、泌尿科和肛肠科等医学领域成为有效的治疗手段,具有手术简单、迅速安全、无需麻醉,不流血、不感染、疤痕小、手术费用低等优点。但目前国内外其它液氮冷冻治疗仪由于没有解决液氮传输技术,均只能用于治疗浅表病灶,对内腔病灶无能为力,这在很大程度上限制了冷冻疗法的应用范围。光纤内窥镜液氮冷冻诊治仪采用负压液氮双相传输技术与光纤内窥镜相耦合,是一种既可检查又能冷     

类单晶PZT纳米纤维的静电纺丝制备探索

以硝酸锆（Zr（NO3）4·5H2O）,乙酸铅（Pb（CH3COO）2·3H2O）,钛酸四丁酯（Ti（OC4H9）4）和聚乙烯吡咯烷酮（PVP）为原料,采用sol-gel和静电纺丝法,结合烧结工艺首次制备了在准同型相界附近的类单晶PZT纳米纤维.利用热重分析、X射线衍射仪、扫描电镜和透射电镜等表征方法,对类单晶PZT纤维的热分解过程、晶体结构、微观相貌和形成机理等进行了分析和解释.研究结果表明：经过400℃预退火0.5h以及750℃烧结2h后,可形成具有类单晶结构的PZT纳米纤维,纤维直径约在80 ～ 100 nm左右,晶体结构为典型的钙钛矿相.形成这种类单晶结构的主要机理是在预退火期,有机物充分分解形成无规则非晶网络,随着烧结温度的升高,取向基本一致的小晶粒经历了形核、长大、吞噬,最终形成类单晶纳米纤维.在准同型相界附近的类单晶PZT纳米纤维在纳米压电器件和微机电系统领域具有广泛的应用前景.     

二硫化钼纳米薄片分散液的剥离制备

文中采用液相超声剥离粉末二硫化钼制备了纳米薄片分散液,通过紫外可见吸收光谱测定分散液的浓度,并探索了超声功率、超声时间以及二硫化钼初始浓度对纳米薄片分散液浓度的影响。实验结果表明,当超声功率为350 W,超声时间为48 h,二硫化钼初始浓度为10 mg/mL时,所制备的纳米薄片分散液浓度可达0.16 mg/mL。在剥离过程中加入聚乙烯吡咯烷酮,可以有效避免由于纳米薄片自身团聚而导致的分散液稳定性差的问题,所得到的二硫化钼纳米薄片分散液可稳定存放超过两个月;同时,PVP的加入可将二硫化钼纳米薄片分散液浓度提高至0.42 mg/mL。     

冷冻治疗慢性肥厚性鼻炎的扫描电镜观察

冷冻治疗慢性肥厚性鼻炎的扫描电镜观察刘慧民李秀芬张亚坤（黑龙江省林业总医院，哈尔滨１５００４０）（黑龙江省电力医院病理科）（哈医大电镜室）利用液氮冷冻治疗慢性肥厚性鼻炎已日益受到国内外专家的重视。Ｏｓｅｎｂｅｒｇｅｒ［１，２］和Ｈｏｌｄｅｎ［３］曾报...     

在硅深－亚微米沟道反应离子刻蚀中气体成分对深度减小的影响

在硅深－亚微米沟道反应离子刻蚀（ＲＩＥ）中，发现氯化气体比氯化气体显然有较大的微－负载效应。为了解作气体效应，利用Ｃｌ２和ＳＦ６进行了模型实验。对腐蚀深度与图形宽度的关系进行了计算，计算时既考虑了腐蚀剂（离子、自由基）的屏蔽效应，也考虑了其表面迁移。根据这些结果，弄清了引起微－负载效应的原因如下：①沟道底部的腐蚀剂的浓度随沟道深度的增加／或沟道宽度的减小而减少；②随着腐蚀剂浓度的改变，氟化气体中刻蚀速率的变化比氯化气体中的大。并且指出，采用较重的卤素作为腐蚀气体，可提供一种去除微－负载效应的方法，因为离子辅助腐蚀在较重的卤素的刻蚀中是占优势的。     

Monodisperse Thermoresponsive Microgels with Tunable Volume‐Phase Transition Kinetics

A facile method to control the volume‐phase transition kinetics of thermo‐sensitive poly(N‐isopropylacrylamide) (PNIPAM) microgels is presented. Monodisperse PNIPAM microgels with spherical voids are prepared using a microfluidic device. The swelling and shrinking responses of these microgels with spherical voids to changes in temperature are compared with those of voidless microgels of the same size and chemical composition prepared using the same microfluidic device. It is shown that the PNIPAM microgels with voids respond faster to changes in temperature as compared with their voidless counterparts. Also, the induced void structure does not have a detrimental effect on the equilibrium volume change of the microgels. Thus, the volume phase transition kinetics of the microgels can be finely tuned by controlling the number and size of the voids. The flexibility, control, and simplicity in fabrication rendered by this approach make these microgels appealing for applications that range from drug delivery systems and chemical separations to chemical/biosensing and actuators.     

Adhesion and Mechanical Properties of PNIPAM Microgel Films and Their Potential Use as Switchable Cell Culture Substrates

Thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM) microgel films are shown to allow controlled detachment of adsorbed cells via temperature stimuli. Cell response occurs on the timescale of several minutes, is reversible, and allows for harvesting of cells in a mild fashion. The fact that microgels are attached non‐covalently allows using them on a broad variety of (charged) surfaces and is a major advantage as compared to approaches relying on covalent attachment of active films. In the following, the microgels’ physico‐chemical parameters in the adsorbed state and their changes upon temperature variation are studied in order to gain a deeper understanding of the involved phenomena. By means of atomic force microscopy (AFM), the water content, mechanical properties, and adhesion forces of the microgel films are studied as a function of temperature. The analysis shows that these properties change drastically when crossing the critical temperature of the polymer film, which is the basis of the fast cell response upon temperature changes. Furthermore, nanoscale mechanical analysis shows that the films posses a nanoscopic gradient in mechanical properties.     

Temperature‐Responsive Substrates: Adhesion and Mechanical Properties of PNIPAM Microgel Films and Their Potential Use as Switchable Cell Culture Substrates (Adv. Funct. Mater. 19/2010)

Thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM) microgel films are shown to allow controlled detachment of adsorbed cells via temperature stimuli. Cell response occurs on the timescale of several minutes, is reversible, and allows for harvesting of cells in a mild fashion. The fact that microgels are attached non‐covalently allows using them on a broad variety of (charged) surfaces and is a major advantage as compared to approaches relying on covalent attachment of active films. In the following, the microgels’ physico‐chemical parameters in the adsorbed state and their changes upon temperature variation are studied in order to gain a deeper understanding of the involved phenomena. By means of atomic force microscopy (AFM), the water content, mechanical properties, and adhesion forces of the microgel films are studied as a function of temperature. The analysis shows that these properties change drastically when crossing the critical temperature of the polymer film, which is the basis of the fast cell response upon temperature changes. Furthermore, nanoscale mechanical analysis shows that the films posses a nanoscopic gradient in mechanical properties.     

Fabrication of Gelatin Microgels by a “Cast” Strategy for Controlled Drug Release

In this paper, we propose a “casting” strategy to prepare intrinsically fluorescent, uniform and porous gelatin microgels with multi‐responsiveness. Gelatin microgels with tunable size were obtained by copying the structure of a porous CaCO₃ template. The diameter of the gelatin microgels was sensitive to salt concentration and pH. Doxorubicin and Rhodamine B as model drugs were loaded into the microgels via electrostatic interaction and release of the payload was triggered by changing the salt concentration and pH, respectively. Cell experiments demonstrated that the gelatin microgels had an excellent biocompatibility and biodegradability. The merits of gelatin microgels such as tunable size, biocompatibility, and stimulus responsive upload and release of positively charged small molecules will permit the microgels as excellent carriers for drug delivery. The whole manufacturing process is furthermore environmental‐friendly involving no organic solvents and surfactants.     

Water‐Soluble Poly(N‐isopropylacrylamide)–Graphene Sheets Synthesized via Click Chemistry for Drug Delivery

Covalently functionalized graphene sheets are prepared by grafting a well‐defined thermo‐responsive poly(N‐isopropylacrylamide) (PNIPAM) via click chemistry. The PNIPAM‐grafted graphene sheets (PNIPAM‐GS) consist of about 50% polymer, which endows the sheets with a good solubility and stability in physiological solutions. The PNIPAM‐GS exhibits a hydrophilic to hydrophobic phase transition at 33 °C, which is relatively lower than that of a PNIPAM homopolymer because of the interaction between graphene sheets and grafted PNIPAM. Moreover, through π–π stacking and hydrophobic interaction between PNIPAM‐GS and an aromatic drug, the PNIPAM‐GS is able to load a water‐insoluble anticancer drug, camptothecin (CPT), with a superior loading capacity of 15.6 wt‐% (0.185 g CPT per g PNIPAM‐GS). The in vitro drug release behavior of the PNIPAM‐GS‐CPT complex is examined both in water and PBS at 37 °C. More importantly, the PNIPAM‐GS does not exhibit a practical toxicity and the PNIPAM‐GS‐CPT complex shows a high potency of killing cancer cells in vitro. The PNIPAM‐GS is demonstrated to be an effective vehicle for anticancer drug delivery.     

From Hybrid Microgels to Photonic Crystals

We have synthesized semiconductor and metal nanoparticles (NPs) in the constrained geometry of polymer microgels. We used electrostatically driven attraction between the ionic groups of the microgels and the precursor cations in the bulk liquid medium to introduce the cations in the interior of the microgel. In the second step, the cations in the microgel interior reacted with the anion (to obtain semiconductor NPs) or they were treated with a reducing agent (to obtain metal NPs). Good control over the size and the concentration of the NPs in the microgel particles was achieved by changing the composition of the corresponding microgel. The doped microgel spheres were heated at pH 4 above the volume‐transition temperature of the polymer to expel the water from the microsphere interior; then the polymer was encapsulated with a hydrophobic polymeric shell. Hybrid core–shell particles were used as the building blocks of the nanostructured material with properties of a photonic crystal.     

In Situ Studies of Surface‐Plasmon‐Resonance‐Coupling Sensor Mediated by Stimuli‐Sensitive Polymer Linker

Hybrid plasmonic nanostructures comprising gold nanoparticle (AuNP) arrays separated from Au substrate through a temperature‐sensitive poly(N‐isopropylacrylamide) (PNIPAM) linker layer are constructed, and unique plasmonic‐coupling‐based surface plasmon resonance (SPR) sensing properties are investigated. The optical properties of the model system are investigated by in situ and scan‐mode SPR analysis. The swelling‐shrinking transitions in the polymer linker brush are studied by in situ contact‐mode atomic force microscopy at two different temperatures in water. It is revealed that the thickness of the PNIPAM layer is decreased from 30 to 14 nm by increasing the temperature from 20 to 32 °C. For the first time the dependence of the coupling behavior in AuNPs is investigated with controlled density on the temperature in a quantitative manner in terms of the change in SPR signals. The device containing AuNPs with optimized AuNP density shows 3.2‐times enhanced sensitivity compared with the control Au film‐PNIPAM sample. The refractive index sensing performance of the Au film‐PNIPAM‐AuNPs is greater than that of Au film‐PNIPAM by 19% when the PNIPAM chains have a collapsed conformation above lower critical solution temperature.     

Poly(N‐isopropylacrylamide)‐Clay Nanocomposite Hydrogels with Responsive Bending Property as Temperature‐Controlled Manipulators

Novel poly(N‐isopropylacrylamide)‐clay (PNIPAM‐clay) nanocomposite (NC) hydrogels with both excellent responsive bending and elastic properties are developed as temperature‐controlled manipulators. The PNIPAM‐clay NC structure provides the hydrogel with excellent mechanical property, and the thermoresponsive bending property of the PNIPAM‐clay NC hydrogel is achieved by designing an asymmetrical distribution of nanoclays across the hydrogel thickness. The hydrogel is simply fabricated by a two‐step photo polymerization. The thermoresponsive bending property of the PNIPAM‐clay NC hydrogel is resulted from the unequal forces generated by the thermoinduced asynchronous shrinkage of hydrogel layers with different clay contents. The thermoresponsive bending direction and degree of the PNIPAM‐clay NC hydrogel can be adjusted by controlling the thickness ratio of the hydrogel layers with different clay contents. The prepared PNIPAM‐clay NC hydrogels exhibit rapid, reversible, and repeatable thermoresponsive bending/unbending characteristics upon heating and cooling. The proposed PNIPAM‐clay NC hydrogels with excellent responsive bending property are demonstrated as temperature‐controlled manipulators for various applications including encapsulation, capture, and transportation of targeted objects. They are highly attractive material candidates for stimuli‐responsive “smart” soft robots in myriad fields such as manipulators, grippers, and cantilever sensors.     

Injection and Self‐Assembly of Bioinspired Stem Cell‐Laden Gelatin/Hyaluronic Acid Hybrid Microgels Promote Cartilage Repair In Vivo

In this paper, a novel bioinspired stem cell‐laden microgel and related in vivo cartilage repair strategy are proposed. In particular, herein the preparation of new stem cell‐laden microgels, which can be injected into the chondral defect site in a minimally invasive way, and more importantly, capable of in situ self‐assembly into 3D macroporous scaffold without external stimuli, is presented. Specifically, thiolated gelatin (Gel‐SH) and vinyl sulfonated hyaluronic acid (HA‐VS) are first synthesized, and then stem cell‐laden gelatin/hyaluronic acid hybrid microgels (Gel‐HA) are generated by mixing Gel‐SH, HA‐VS, and bone mesenchymal stem cells (BMSCs) together via droplet‐based microfluidic approach, followed by gelation through fast and efficient thiol‐Michael addition reaction. The encapsulated BMSCs show high viability, proliferation, and chondrogenic differentiation potential in the microgels. Moreover, the in vitro test proves that BMSC‐laden Gel‐HA microgels are injectable without sacrificing BMSC viability, and more importantly, can self‐assemble into cartilage‐like scaffolds via cell–cell interconnectivity. In vivo experiments further confirm that the self‐assembled microgels can inhibit vascularization and hypertrophy. The Gel‐HA microgels and relevant cartilage repair strategy, i.e., injecting BMSC‐laden microgels separately and reconstructing chondral defect structure by microgel self‐assembly, provides a simple and effective method for cartilage tissue engineering and regenerative medicine.     

Surface-Bound Microgels for Separation,Sensing, and Biomedical Applications

This study presents a comprehensive survey of microgel-coated materials and their functional behavior, describing the complex interplay between the physicochemical and mechanical properties of the microgels and the chemical and morphological features of substrates. The cited literature is articulated in four main sections: i) properties of 2D and 3D substrates, ii) synthesis, modification, and characterization of the microgels, iii) deposition techniques and surface patterning, and iv) application of microgel-coated surfaces focusing on separations, sensing, and biomedical applications. Each section discusses – by way of principles and examples – how the various design parameters work in concert to deliver functionality to the composite systems. The case studies presented herein are viewed through a multi-scale lens. At the molecular level, the surface chemistry and the monomer make-up of the microgels endow responsiveness to environmental and artificial physical and chemical cues. At the micro-scale, the response effects shifts in size, mechanical, and optical properties, and affinity towards species in the surrounding liquid medium, ranging from small molecules to cells. These phenomena culminate at the macro-scale in measurable, reversible, and reproducible effects, aiming in a myriad of directions, from lab-scale to industrial applications.