聚合物纳流控通道的溶剂蒸发辅助自封闭机理研究

Polymers have been pursued as an alternative substrate for nanofluidic devices for its chemical stability, biocompatibility and easy fabrication with low cost. Sealing between the structure substrate and the cover is the key technique for the manufacture of nanofluidic chips and directly affects the quality of fabricated products. Based on the different interface effects, many sealing methods were developed for the fabrication of nanofluidic channels. Channel sealing with easy fabrication and well controlled dimensions is an urgent obstacle remaining unsolved due to lack of fully understanding the interface effect between the enclosed layers.. In this proposal, we present a novel fabrication method for generating polymer nanofluidic channels by exploiting solvent-assisted self-sealing of PMMA solution, in which the channel is enclosed by its self induced by diffusion and evaporation into poly(dimethylsiloxane) (PDMS) cover. Firstly, polymeric nano trenches fabricated by nanoimprint are filled by polymer solution with selective dewetting technique. The trenches substrate and PDMS cover layer are brought together and then a vertical capillary motion of PMMA solution into PDMS layer can give birth to hollow structures with an embedded cavity under certain conditions. . To investigate the self-sealing mechanism, a transient semi-infinite mass transport model is developed to predict the behavior of the moving solution/cavity front in the trench, based on the property of polymer chain motion induced by solution evaporation. Molecular simulation method is employed to demonstrate the physical mechanism during the formation and variation of the embedded cavity. Real time monitoring by intensity of diffracted light has been proposed to control the seal-sealing process precisely. The property of gas transport through the nanochannels is systematically investigated to classify the interaction between the section dimensions and helium. We propose a new principle to characterize the channel dimension through the molecular flow conductance measurement. By this way, the dimension of sealed channels is measured to reveal the sealing rules and features affected by polymer concentration, molecular weight of polymer chain, and wettability of trenches.. This proposal should provide fundamental contributions to demonstrate large scale easy fabrication of micro/nano fluidic system with well controlled dimensions, low cost and high throughput.

聚合物纳流控通道的封闭是该类器件制造和应用的关键技术前提，如何利用沟槽结构和贴合盖片之间的界面效应，实现高效、尺寸可控的通道封闭一直是亟待解决的问题。本项目根据聚二甲基硅氧烷 (PDMS)多孔渗透性能，提出基于溶剂蒸发辅助效应实现聚合物通道自封闭的新理论，利用气体流导表征通道尺度，研究通道自封闭形成机理。基于沟槽内溶剂通过PDMS蒸发过程中聚合物分子迁移特性，构建溶剂扩散作用导致的自封闭空腔界面移动模型，仿真分析聚合物迁移过程中自封闭空腔形成和变化的物理机制。通过实时测量衍射光强量化控制聚合物通道自封闭过程；研究气体传输特性与通道截面尺寸的耦合规律，发展分子流流导表征通道截面尺寸的新原理。通过尺寸测试结合自封闭模型阐释通道结构尺寸与聚合物浓度、溶剂种类、沟槽结构和聚合物分子重量等因素的响应机制。研究结果将为聚合物纳流控通道简单高效的可控密封和微纳结构尺度表征提供理论依据和新方法。

目前的聚合物微纳流控通道封闭技术在方法适用性和封装效率等方面还存在问题，一直是制约纳流控系统批量化和器件化制造的瓶颈。结合聚合物材料特性进一步研究其在微纳沟槽界面的边界效应，寻找尺度可控、简单高效的通道封闭机理是微纳流控器件制作的关键问题。本项目提出了一种提出基于溶剂蒸发辅助效应实现聚合物通道自封闭的新方法，利用气体流导表征通道尺度，探究通道自封闭形成机理，通过实时测量衍射光强量化控制聚合物通道自封闭过程，自封闭过程的量化控制。为聚合物纳流控通道简单高效的可控密封和微纳结构尺度表征提供理论依据和新方法。主要工作和成果综述如下：.1、基于沟槽内溶剂通过PDMS蒸发过程中聚合物分子迁移特性，构建溶剂扩散作用导致的自封闭空腔界面移动模型，仿真分析聚合物迁移过程中自封闭空腔形成和变化的物理机制；.2、优化溶剂蒸发辅助自封闭纳米通道制作工艺，研究溶剂种类、聚合物浓度、沟槽结构和表面能等因素对自封闭过程的影响，成功制作出微米和纳米尺度的聚合物流控通道；.3、发展基于实时监测的通道自封闭工艺过程的量化控制技术，利用封闭通道负一级衍射强度随通道尺寸变化的特性，通过监测衍射强度掌控通道自封闭的过程；.4、提出了一个表征纳米结构尺寸的新方法，即利用分子流状态下气体在纳米通道传输流导恒定特性，推导出纳米通道的结构尺寸，发展了差压法、质谱法和动态差压衰减法等气体传输特性表征方法，建立气体传输特性与通道截面尺寸的耦合规律的通道截面尺寸表征新原理；.5、研制出多种纳流控通道与测试系统封接新方法，采用玻璃封接和熔融封接技术解决硅与金属热膨胀系数不匹配的问题，获得了低于-11 Pa m3/s的极低本低漏率的纳流控通道和金属封接结构；.6、将纳流控通道应用于微纳流量传输控制测试方面，在航天和大科学工程等方面真空检漏计量方面取得示范应用。

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