Polymer end group modifications and polymer conjugations via “click” chemistry employing microreactor technology

This study presents the development of microreactor protocols for the successful continuous flow end group modification of atom transfer radical polymerization precursor polymers into azide end‐capped materials and the subsequent copper‐catalyzed azide alkyne click reactions with alkyne polymers, in flow. By using a microreactor, the reaction speed of the azidation of poly(butyl acrylate), poly(methyl acrylate), and polystyrene can be accelerated from hours to seconds and full end group conversion is obtained. Subsequently, copper‐catalyzed click reactions are executed in a flow reactor at 80 °C. Good coupling efficiencies are observed and various block copolymer combinations are prepared. Furthermore, the flow reaction can be carried out in only 40 min, while a batch procedure takes several hours to reach completion. The results indicate that the use of a continuous flow reactor for end group modifications as well as click reactions has clear benefits towards the development and improvement of well‐defined polymer materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1263–1274     

Size-resolved counting of circulating tumor cells on pinched flow-based microfluidic cytometry

Precise cell detecting and counting is meaningful in circulating tumor cells (CTCs) analysis. In this work, a simple cyclic olefin copolymer (COC) microflow cytometer device was developed for size-resolved CTCs counting. The proposed device is constructed by a counting channel and a pinched injection unit having three channels. Through injection flow rate control, microspheres/cells can be focused into the centerline of the counting channel. Polystyrene microspheres of 3, 9, 15, and 20 µm were used for the microspheres focusing characterization. After coupling to laser-induced fluorescence detection technique, the proposed device was used for polystyrene microspheres counting and sizing. A count accuracy up to 97.6% was obtained for microspheres. Moreover, the proposed microflow cytometer was applied to CTCs detecting and counting. To mimic blood sample containing CTCs and CTCs mixture with different subtypes, an MDA-MB-231 (human breast cell line) spiked red blood cells sample and a mixture of MDA-MB-231 and MCF-7 (human breast cell line) sample were prepared, respectively, and then analyzed by the developed pinched flow-based microfluidic cytometry. The simple fabricated and easy operating COC microflow cytometer exhibits the potential in the point-of-care clinical application.     

The Barton reaction using a microreactor and black light. Continuous-flow synthesis of a key steroid intermediate for an endothelin receptor antagonist

The Barton reaction (nitrite photolysis) of a steroidal substrate 1, to give 2, a key intermediate for the synthesis of an endothelin receptor antagonist, was successfully carried out in a continuous microflow system using a pyrex glass-covered stainless-steel microreactor having a microchannel (Type A: 1000 μm width, 107 μm depth, 2.2 m length). We found that a 15 W black light (peak wavelength: 352 nm) as the light source, suffices for the Barton reaction, creating a compact photo-micro reaction system. Multi-gram scale production was attained using two serially connected, multi-lane microreactors (Type B).     

横向电动效应作用下微混合的数值模拟

微流体机械系统中电渗流的雷诺数一般都比较低,微通道内的混合主要通过扩散来完成,因此需要较长的距离和时间才能混合均匀.本文在一个二维微通道内施加横向电场,并讨论了不同横向电场强度、微电极对布置情况、壁面zeta电势等因素对微混合的影响.结果表明此方法可以有效地提高混合效率,增加横向电场强度和电极对密度可以明显提高混合效率,较小的zeta电势可以获得更好的混合效果.     

粗糙微通道内气体流动的分子动力学研究

为研究粗糙度对微通道内气体流动及其边界滑移性质的影响,采用分子动力学模拟方法研究了氩气在0.1 μm铂通道内的流动,通道表面粗糙度由三角粗糙元阵列构成。气体流动的边界条件决定于2个准则数: A/λ和Kn=λ/L(其中A为壁面粗糙度、λ为气体分子的平均自由程、L为流动系统的尺度)。Maxwell基于Kn的滑移模型当A/λ<0.25时适用;A/λ<1时,气体流动存在边界速度滑移,体现出稀薄效应,A/λ≈1时为无滑移,A/λ>1时为等效负滑移.     

Navier-Stokes方程二阶速度滑移边界条件的检验

对微尺度气体流动,Navier-Stokes方程和一阶速度滑移边界条件的结果与实验数据相比,在滑移区相互符合,在过渡领域则显著偏离.为改善Navier-Stokes方程在过渡领域的表现,有些研究者尝试引入二阶速度滑移边界条件,如Cercignani模型,Deissler模型和Beskok-Karniadakis模型.以微槽道气体流动为例,将Navier-Stokes方程在不同的二阶速度滑移模型下的结果与动理论的直接模拟Monte Carlo(DSMC)方法和信息保存(IP)方法以及实验数据进行比较.在所考察的3种具有代表性的二阶速度滑移模型中,Cercignani模型表现最好,其所给出的质量流率在Knudsen数为0.4时仍与DSMC和IP结果相符;然而,细致比较表明,Cercignani模型给出的物面滑移速度及其附近的速度分布在滑流区和过渡领域的分界处(Kn=0.1)已明显偏离DSMC和IP的结果.     

微尺度空泡溃灭驱使微球运动的机理研究

受限空泡的溃灭是气泡动力学的核心问题,研究表明毫米尺度的空泡溃灭可以拉动附近同尺度的悬浮颗粒运动.本文针对受限空泡溃灭在微尺度下的行为开展研究,通过气泡驱动的球形微马达实验,给出了微气泡溃灭形成射流从而显著推动马达前进的现象,但由于溃灭时间很短,Micro PIV系统不能给出足够的流动细节.进而采用基于流体体积的数值手段模拟了这一过程,获得了流场的时空分布,并通过积分估算了微球获得的冲量,给出了微球所能达到的速度.结果表明这一问题与尺度密切相关,微尺度下空泡溃灭足以推动微球显著运动,在气泡尺寸固定的情况下,微球半径越小,微球与气泡间距离越近,推动的效果越明显.冲量定理则定性地解释了宏观尺度与微尺度下存在差异的原因.这一特殊的微流动问题不但扩展了空化研究的尺度范围,揭示了微尺度下空泡与颗粒作用的特性,而且对提高微马达的驱动效率也具有重要意义.     

双电层交叠时微通道内流动的数值模拟

本文采用有限容积法数值模拟了在电动效应作用下微通道内流体的流动特性。分别采用Poisson方程和Nernst- Planck方程计算电动势和离子浓度分布。结果表明在双电层相互交叠的情况下,微通道内轴向的流动电势先减小后增大,并逐渐趋于定值,从而导致了轴向电动效应不断增强。     

Microflow injection chemiluminescence system with spiral microchannel for the determination of cisplatin in human serum

A new microflow injection chemiluminescence (μFI-CL) system was described for the determination of cisplatin in human serum. By using the microchip with double spiral channel configuration, the sensitivity was greatly enhanced due to more efficient mixing of the analyte and reagent solutions. Experimental results revealed that common ions in human serum, such as Mn²⁺, Co²⁺, Fe³⁺, Cu²⁺, Zn²⁺, Ni²⁺, Na⁺, K⁺, Ca²⁺, Cl⁻, NO₃⁻, Ac⁻, CO₃²⁻, PO₄³⁻, SO₄²⁻ did not cause interference with the detection of Pt(II) by using 1,10-phenanthroline as the masking agent. Under the optimized conditions, a linear calibration curve (R² = 0.998) over the range 2.0 × 10⁻⁸ to 2.0 × 10⁻⁶ mol L⁻¹ was obtained with the detection limit of 1.24 × 10⁻⁹ mol L⁻¹. The relative standard deviation was found to be 3.46% (n = 12) for 2.0 × 10⁻⁷ mol L⁻¹. The sample consumption was only 2 μL with the sample throughput of 72 h⁻¹. It had been used for trace platinum determination in cisplatin injection and human serum samples after the dosage of cisplatin. The recovery varied from 97.6 to 103.9%. The results proved that the proposed μFI-CL system had the advantages of high sensitivity and precision, low sample and reagents consumption, and high analytical throughput.