聚合物微流控芯片的简易热压制作及其应用

提出聚甲基丙烯酸甲酯(PMMA)微流控分析芯片的一种简易热压制作法,研究了采用外径为180μm的毛细管作为压制微通道"模具"时的条件及相应的PMMA基片的热封合条件。采用扫描电镜(SEM)对PMMA芯片的微通道及其横截面形貌进行了表征,并测定了PMMA芯片电渗流,其电渗流值与文献报道值基本一致,上述结果表明本方法实现了热压封接。另外,芯片电泳-激光诱导荧光及共聚焦荧光显微镜检测技术表明该方法制作的PMMA芯片能稳定且均一地固定蛋白固定相,并成功实现色氨酸对映体的手性分离,两者的有效踏板数分别为450000和19000m-1。     

微流控芯片系统中测温及控温装置的研制

报道了一种结构简单、成本低、操作方便、应用于微流控芯片系统中温度测量及温度控制的装置。该系统以CCD摄像机、荧光显微镜及图像采集卡构成的非接触荧光指示剂测温装置,实现了微流体空间温度分布测量以及随时间变化的温度测量。提出了以透明氧化铟锡薄膜玻璃作为加热元件,采用PID控制算法的温度控制平台,稳态时温度控制精度可达到±0.1 ℃。采用该测温和控温装置研究了玻璃微流控芯片微通道内溶液温度在空间上和随时间的变化情况,结果表明该方法简单、有效,可达到μm级的空间分辨率和ms级的时间分辨率。     

微流控SERS芯片及其生物传感应用

由于微流控芯片具有优异的集成性和灵活的可操作性,基于芯片上的检测方法被大量开发,发展十分迅速。其中,表面增强拉曼光谱（SERS）凭借其超高的灵敏度、独一无二的指纹谱和窄峰宽等特点成为一种广泛采用的检测手段。SERS微流控芯片集SERS检测技术与微流控芯片的优势于一体,一方面为SERS检测方法的重复性和可靠性提供了一个高效平台,另一方面推动了微流控芯片的功能拓展,在生物分子探测、细胞捕获乃至组织模拟等领域具有广阔的应用前景。本文在简要介绍SERS的原理及其生物传感应用的基础上,重点概述了SERS微流控芯片的构建及其在生物传感及检测中的应用,最后探讨了该研究方向存在的问题及发展方向。     

微流控芯片流道特征超声C扫描分析

微流控芯片流道宽度处于微米尺度,存在特征辨识困难的问题。该文选取两种具有不同流道宽度和布局的典型微流控芯片,采用超声C扫描技术进行流道特征成像。利用标称中心频率15 MHz、10 MHz和5 MHz聚焦探头实施水浸C扫描检测,并分析中心频率、焦斑直径、扫描步进等关键参数对流道表征的影响。实验结果表明,对于流道宽度200μm的微流控芯片,当探头中心频率不低于10 MHz、扫描步进不超过0.1 mm时,成像分辨力和流道表征效果最佳,且流道中心间距测量误差不超过5%。同时,超声C扫描图像可以反映流道宽度变化,辨识发生堵塞的微流控芯片。     

基于微流控芯片的臭氧化学发光法测量海水化学需氧量(COD)分析系统的研究

海水化学需氧量(COD)是海水中有机污染物的综合指标, 是海洋环境监测最重要的项目之一。现有的海水COD测量方法耗时长、体系复杂,无法满足海洋在线监测的需求。采用臭氧发光机理实现海水COD的分析,同时借助微芯片技术,设计了高集成度的新型海水COD分析系统,同时对系统中臭氧和水样流速、水样加热温度、样品盐度及过滤精度等影响测定的因素进行优化筛选。实验结果表明,该系统的测量范围为0.1～10 mg·L-1,检出限0.08 mg·L-1,与国标方法测量结果有很好的一致性,同时具有结构简单,测试时间短等优势,满足海水COD现场分析的需求。     

夹心式太赫兹微流控芯片

许多生物大分子的振动和转动能级都落在THz波段范围内,因此可以采用THz光谱技术定性地鉴别生物样品。但是大部分生物分子的活性需在液体环境中才能表现出来,而水作为极性物质对THz波具有较强的吸收特性。因此,在THz光谱技术中通常采取各种措施来减少水的影响,以防止水溶液中生物样品的信息被掩盖。该研究设计了两种可利用透射式太赫兹时域光谱(THz-TDS)系统检测的夹心式微流控芯片,通过减小THz与水的作用距离来减少水对THz的吸收,从而达到高透过率的目的。微流控芯片采用环烯烃共聚物(Zeonor 1420R)作为基片和盖片,聚二甲基硅氧烷(PDMS)作为沟道夹层,利用THz-TDS系统对该芯片进行了测试,测得该芯片在0.2～2.6 THz频率范围内的透过率可以达到80％以上。在微流控芯片中分别加入去离子水、1,2-丙二醇以及二者在不同体积比下的混合溶液,并测量了它们的透射谱。结果表明,不同比例溶液的THz光谱明显不同,说明该芯片在测量液态样品方面的可行性。此外,用该芯片分别研究了不同浓度的氯化钾和碘化钾溶液,发现氯化钾溶液随着浓度的增加THz透过率减弱,而碘化钾溶液则相反。初步认为,电解质改变了水溶液中的氢键密度,从而导致溶液对THz吸收的改变。     

微流控光谱分析进展

本文对新兴的微型分析技术———微流控分析中的光谱检测技术进行了综合评述 ,简介了微流控分析技术 ,并对该分析方法进行了展望     

PDMS微流控芯片中焦耳热效应的数值研究

用数值模拟的方法对矩形通道微流控芯片中由于焦耳热效应而产生的温度场分布进行了分析.通过求解耦合的动量以及能量方程,得到了PDMS/PDMS芯片中温度场的瞬态发展过程.对稳定状态下不同缓冲溶液浓度,底片材质以及厚度的芯片中的温度场分布也做了比较和分析.结果表明,相比于PDMS/PDMS芯片,相同条件下PDMS/玻璃芯片中的焦耳热效应会减小很多,而缓冲溶液浓度以及芯片厚度对缓冲溶液的出口平均温度也有显著影响.最后提出了减小焦耳热效应的方法.     

基于微流控芯片的电解质溶液太赫兹吸收特性研究

由于许多生物分子的振动和转动能级均在太赫兹波段,且太赫兹波具有电子能量低（约4 meV）,不会破坏待测样品的特性,因此可以采用太赫兹光谱技术检测生物样品。然而许多生物分子在液体环境中才能保持其生物活性,需要在盐溶液中来探究酸碱环境对其的影响,以及在盐类缓冲液中研究其生物特性。但水作为极性液体对太赫兹波有强烈的吸收,因此,探究如何减少水对太赫兹吸收的方法非常必要。水对太赫兹的吸收主要因水分子间氢键造成,现阶段最常见的方法是减少水与太赫兹波的作用距离以及破坏水分子间的氢键。利用夹心式微流控芯片在太赫兹时域光谱系统下通过观察光谱强度变化来探究电解质对水分子间氢键的影响,既减少了水和太赫兹波的作用距离,又探究了电解质对水分子间氢键的作用。在微流控芯片中分别加入不同种类以及不同浓度的电解质,通过观察其在0.1～1.0 THz范围内的光谱强度变化来分析不同电解质对水分子间氢键的影响。部分电解质促进氢键的缔合,而另一部分则破坏氢键的形成,在太赫兹光谱范围内表现为光谱强度的变化。若促进氢键的缔合则对太赫兹吸收变大,光谱强度减弱;若破坏氢键的缔合则对太赫兹吸收减弱,光谱强度增加。研究结果发现：在水中加入KCl和KBr时,太赫兹光谱强度增加,表明二者对氢键有破坏作用,使得光谱强度变大;然而当加入MgCl₂和CaCl₂时,太赫兹光谱强度减弱,表明二者对氢键有缔合作用,从而使光谱强度变小。利用太赫兹技术在0.1～1.0 THz范围内研究KCl,KBr,MgCl₂和CaCl₂这四种不同浓度的电解质溶液特性,发现它们只会对光谱强度造成一定影响,不会引入新的特征吸收峰以及对待测样品造成干扰。这对于研究诸如大肠杆菌、枯草芽孢杆菌等在0.1～1.0 THz范围内有特征吸收谱的生物分子具有一定的实用价值。在溶液中加入所需的电解质并借助微流控芯片不仅可以识别待测样品、研究待测样品的光谱信息、探究其生物特性,而且为进一步推动太赫兹技术在生化方面的应用研究提供了先决条件。     

玻璃微流控芯片表面改性的微观机理研究

在玻璃微流控芯片通道表面用硅烷化试剂二氯二甲基硅烷进行处理后，二氯二甲基硅烷与玻璃通道表面的硅羟基反应，硅烷基覆盖在原来的硅羟基上，其结果为电渗流减小甚至完全消除.进一步采用全势能线性糕模轨道分子动力学方法，对表面反应的微观结构进行了理论计算，计算结果表明硅羟基中的氢原子与二氯二甲基硅烷中的氯原子结合形成稳定的HCl分子结构而脱离，从而使硅烷基覆盖在表面上. 关键词： 微流控芯片 二氯二甲基硅烷 分子动力学方法 微观稳定结构     

聚甲基丙烯酸甲酯中乙酰丙酮铕水合物掺杂形成的差异化发光中心

制备了均匀且透明的乙酰丙酮铕水合物掺杂的聚甲基丙烯酸甲酯(PMMA)。Judd-Ofelt强场参数Ω2(19.73×10-20 cm2)和Ω4(2.19×10-20 cm2)表明在掺杂样品中三价铕离子周围环境具有较强共价性和反演非对称性。计算得5 D0→7 FJ(J=1,2和4)跃迁的最大发射截面分别为0.38×10-21,4.90×10-21和0.36×10-21 cm2。在365nm紫外光的激发下样品发出紫红色荧光,在254nm紫外光激发下则呈现明亮的红色,表明样品可作为紫外光敏感元件用于光学传感器。掺杂样品折射率与纯PMMA的折射率之间存在合理的差值,当其作为纤芯材料与包层材料纯PMMA结合制成标准尺寸9μm/125μm光纤时支持多模光传输,为进一步研发医疗照明光纤、柔性通讯光纤和光纤传感器提供基础。     

Phase Separation in Poly(Methyl Methacrylate)-Epoxy Blend

Diglycidyl ether of bisphenol A (DGEBA) epoxy resin was modified with high molecular weight poly(methyl methacrylate) (PMMA). Morphological variations of a 2 wt% PMMA-modified epoxy mixture were studied by optical microscopy and scanning electron microscopy (SEM). A PMMA-epoxy blend cured at 100°C revealed that a secondary phase morphology was observed in both epoxy and PMMA phases from the early stages of the phase separation process. A morphology consisting of a rough striated continuous phase along with large smooth regions was observed by SEM, confirming the secondary phase separation. The dynamic mechanical thermal analysis showed that the PMMA modification of epoxy at such a low PMMA concentration of 2 wt% has no major influence on the glass transition temperature of the epoxy-rich phase. The PMMA-epoxy blend showed a slight increase in the flexural properties and the fracture toughness.     

Effect of Individualized Cellulose Fibrils on Properties of Poly(Methyl Methacrylate) Composites

Cellulose fibrils were manufactured from flax fibers using chemical treatments followed by cryo-crushing and ultrasonication techniques. The fibrils, consisting mainly of cellulose free from lignin, pectin and hemicellulose, were exploited as a biofiller in preparing poly(methyl methacrylate) (PMMA) matrix composites. The effects of incorporating cellulose fibrils on the physical and mechanical properties of the polymer matrix were investigated. In particular, the influence of the fibrils on the thermal stability and degradation of the composites was studied by means of thermogravimetric analysis carried out in both inert and oxidative atmospheres. The runs performed under air flow revealed the efficiency of the cellulose fibrils in delaying the polymer decomposition during thermal oxidation. The weight loss was slowed down in the composites of all compositions and the temperature of degradation increased with increasing the amount of the fibrils. The combustion properties of the fibril-based composites were evaluated by means of pyrolysis combustion flow calorimetry. The addition of cellulose fibrils into the PMMA matrix resulted in a noticeable decrease of the primary combustion parameters.     

Bonding at Compatible and Incompatible Amorphous Interfaces of Polystyrene and Poly(Methyl Methacrylate) Below the Glass Transition Temperature

Abstract

Films of high‐molecular‐weight amorphous polystyrene (PS, M _w = 225 kg/mol, M _w/M _n = 3, T _g‐bulk = 97°C, where T _g‐bulk is the glass transition temperature of the bulk sample) and poly(methyl methacrylate) (PMMA, M _w = 87 kg/mol, M _w/M _n = 2, T _g‐bulk = 109°C) were brought into contact in a lap‐shear joint geometry at a constant healing temperature T _h, between 44°C and 114°C, for 1 or 24 hr and submitted to tensile loading on an Instron tester at ambient temperature. The development of the lap‐shear strength σ at an incompatible PS–PMMA interface has been followed in regard to those at compatible PS–PS and PMMA–PMMA interfaces. The values of strength for the incompatible PS–PMMA and compatible PMMA–PMMA interfaces were found to be close, both being smaller by a factor of 2 to 3 than the values of σ for the PS–PS interface developed after healing at the same conditions. This observation suggests that the development of the interfacial structure at the PS–PMMA interface is controlled by the slow component, i.e., PMMA. Bonding at the three interfaces investigated was mechanically detected after healing for 24 hr at T _h = 44°C, i.e., well below T _g‐bulks of PS and PMMA, with the observation of very close values of the lap‐shear strength for the three interfaces considered, 0.11–0.13 MPa. This result indicates that the incompatibility between the chain segments of PS and PMMA plays a negligible negative role in the interfacial bonding well below T _g‐bulk.     

Effect of Molecular Architecture on Physical Properties of Tree-Shaped and Star-Shaped Poly(Methyl Methacrylate)-Based Copolymers

The synthesis of star-like A(B)_n copolymers based on the hydrophilic poly(ethylene glycol) monomethyl ether (m-PEG, block A) and the hydrophobic poly(methyl methacrylate) (PMMA, blocks B) is reported. We obtained copolymers made of one m-PEG chain and 2 or 4 PMMA blocks using a combined “arm first”—“core first” approach. Such structures were called tree-shaped copolymers where the m-PEG was considered as the trunk and PMMA arms as the branches. Star-like copolymers (B)_nA-A(B)_n built by two tree-shaped fragments with a poly(propylene oxide) (PPO) as the central junction, were also synthesized according to a previously reported procedure. The latter were called star-shaped structures and the synthesis was performed to obtain architectures different from the tree-shaped one but characterized by a similar length of the PMMA arms. Microstructural analysis was carried out through ¹H-NMR and GPC, and the thermal and transport properties (sorption and diffusion) to liquid water were investigated and correlated to the molecular architecture of the two classes of copolymers.     

Thermal Stability and Degradation Kinetics of Poly(Methyl Methacrylate)/Sepiolite Nanocomposites by Direct Melt Compounding

Poly(methyl methacrylate) (PMMA) nanocomposites based on sepiolite modified with trimethyl hydrogenated tallow amine by an adsorption process were prepared by melt compounding using a corotating twin screw extruder. The morphology and dispersion of sepiolite in the PMMA were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability and the activation energies were investigated by thermogravimetric analysis/differential thermogravimetric (TGA/DTG). The XRD and TEM results show that the sepiolite was dispersed homogeneously in the PMMA matrix at a nanometer scale. The TGA analysis revealed that the addition of sepiolite improved the thermal stability of PMMA. The apparent activation energies were calculated by the method of Flynn–Wall–Ozawa in nitrogen at four different heating rates, showing that sepiolite increased the apparent activation energies by about 20 kJ/mol within the degree of conversion (α) of 0.35–0.9, as compared with the reference PMMA sample.     

Parametric Studies on the Grafting of Poly(Methyl Methacrylate) onto Organophilic Montmorillonite Using Silylated Clay Platelets

Poly(methyl methacrylate) (PMMA)/organophilic montmorillonite (Cloisite 30B) nanocomposites were synthesized by the chemical grafting of PMMA onto Cloisite 30B via solution polymerization of methyl methacrylate (MMA) with vinyl-modified organoclay. The effects of different parameters such as clay weight percent (CWP), solvent per monomer volume ratio, and dispersion time on the properties of the PMMA grafted Cloisite 30B were investigated using the Taguchi experimental design method. This method gives a much-reduced variance for the experiments with optimum setting of control parameters and provides a set of minimum experiments compared to the conventional methods. Qualitative evidence for the chemical grafting of the PMMA onto Cloisite 30B was confirmed by Fourier transform infrared spectroscopy (FT-IR). X-ray diffraction (XRD) was used to investigate interlayer changes of the clay in the grafted nanoplatelets. The exfoliated/intercalated morphology of the nanocomposites was confirmed by XRD. Furthermore, thermal properties were measured by thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). Statistical analysis of results revealed that clay weight percent and solvent per monomer ratio had significant effects on the properties of final products. The percent of grafted PMMA and storage modulus of PMMA/30B nanocomposites decreased with increasing clay content due to better dispersion of the clay at lower loadings. On the other hand, because of a tendency to formation of homopolymer and oligomers at higher solvent loadings; the percent of grafted PMMA, storage modulus and glass transition temperature of PMMA/30B nanocomposites decreased with an increase in solvent per monomer volume ratio. However, the obtained PMMA/30B nanocomposites at the optimum conditions, was exhibited a higher glass transition temperature, higher storage modulus and better thermal stability than the pure PMMA.     

无规聚甲基丙烯酸甲酯立构复合的红外光谱研究

用红外光谱研究了无规聚甲基丙烯酸甲酯的丙酮、苯、氯仿溶液成膜样品的立构复合状况。结果表明无规聚甲基丙烯酸甲酯在丙酮和苯中确能形成立构复合结构,结构的形成主要是依靠分子链中间规和等规链段的相互作用。对丙酮样品的退火实验表明,在退火过程中能够发生间规链段的自聚集现象。     

Electrical conductivity behaviour of pure and polyblends samples of polyvinyl chloride (PVC) and polymethyl methacrylate (PMMA)

Electrical conductivity of pure PVC, PMMA and their polyblends samples has been studied in detail as a function of polarizing fields at constant temperatures. Different plots were drawn to investigate the nature of mechanism responsible for conduction. The nature of all the thermograms is nonlinear but similar for all temperatures. The plots have two slopes, i.e., ohmic conduction with slope of curve ≈1 at lower voltage region and a non-ohmic conduction with slope ≈1.9 at higher voltage region are observed. The increase in the conductivity and decrease in the activation energy, suggest that plasticization effect is taking place between the polymers when they are blended. Fowler–Nordheim plots are not consistent and showing negative and positive slopes simultaneously for lower as well as higher values of applied voltage. Theoretical and experimental values of β_SR and β_PF were calculated and the β_exp of pure and polyblend samples is in agreement with theoretically β_PF. The β_exp value lies close to β_PF, this shows that Poole–Frenkel mechanism is also effective. The calculated metal electrode potential barrier at a constant voltage suggests that the dominant charge carrier mechanism is Schottky–Richardson type. Hence in the present case both SR and PF mechanisms are seem to be operative.     

基于新型聚合物碳糊复合电极的电致化学发光研究

以甲基丙烯酸甲酯(MMA)预聚物作为石墨粉的粘合剂,完全聚合固化,制备并表征了聚合物碳糊复合电极.基于此电极考察了鲁米诺体系的电致化学发光行为.在最优条件下,鲁米诺在聚合物碳糊电极上的电化学响应比在传统的碳糊电极上明显增强,电致化学发光的稳定性和发光强度也大大增加.利用尿酸对该体系发光的强抑制作用,建立了尿酸的电致化学发光检测方法,线性范围为8×10-11-3×10-8mol/L,检出限为1.2×10-11 mol/L,应用于体液测定,结果满意.