Study on the flow behavior of DNA polymer dispersion

我们研究了DNA聚合物在与DNA分析分子操作相关的微流中的伸长或对齐行为。本项目还考察了DNA聚合物分散体作为功能流体的适用性。此外，它有望获得元素数据的分子运动建模的聚合物动力学模拟。在这些观点中，我们主要进行了微流的研究。利用荧光显微镜直接观察了DNA聚合物在微通道中突然收缩、l形角和t形接头的变形行为。在这种复杂的流场中，各种变形或伸长模式被阐明。此外，还澄清了DNA聚合物在伸长和剪切结合流动中比在纯伸长流动中获得更有效的延伸。此外，由于t型连接通道比l型角流产生更高的延伸速率，t型通道有利于DNA聚合物的延伸。用同一显微镜观察了DNA聚合物在微库埃特流中的行为。观察了启动流动时聚合物的延伸规律和停止流动后DNA聚合物的松弛过程。结果表明，在弛豫过程中，DNA聚合物的长度随时间呈指数递减。利用机械和光学流变仪测量了DNA聚合物溶液的宏观性质。在稳定剪切流的双折射测量中，双折射随剪切速率的增加而增加，取向角随剪切速率的增加而减小。认为这种倾向可能与DNA聚合物的延伸和排列有关。

We have investigated elongational or aligning behaviors of DNA polymers in micro flows related to molecular manipulations for DNA analysis. Applicability of DNA polymer dispersions as a functional fluid is also examined in this project. Moreover, it was expected to obtain elemental data for the modeling of molecular motions in polymer dynamics simulations.In these view points, we have mainly conducted studies with micro flows. Deformation behaviors of DNA polymers in micro channels with an abrupt contraction, an L-shaped corner or a T-shaped joint have been directly observed using a fluorescence microscope. Various deformation or elongation patterns were clarified in such complex flow fields. It was also clarified that more effective extension of DNA polymers was obtained in combined elongational and shear flows than in purely elongational flows. Moreover, since the T-shaped joined channel generates a flow with higher elongational rate than that in the L-shaped corner flow, the T-shaped channel was helpful for the DNA polymer extension. The behaviors of DNA polymers in micro Couette flow were also observed with the same microscope. Polymer extending patterns in a start up flow and relaxation process of DNA polymers after cessation of the flow were observed. It is clarified that the length of DNA polymers decreases exponentially with time in the relaxation process.Macroscopic properties of DNA polymer solution were also measured utilizing rheometers with mechanical and optical devices. In the measurement of birefringence in steady shear flows, the increase in birefringence and decrease in orientation angle with shear rate increase were obtained. It is considered that these tendency would be related to the extension and alignment of DNA polymers.