Reactive deposition of nano-films in deep polymeric microcavities
Reactive deposition of nano-films in deep polymeric microcavities
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DOI：
10.1039/c2lc40296c
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发表时间：
2012-11-21
期刊：
影响因子：
6.1
通讯作者：
Lee, Luke P.
中科院分区：
文献类型：
--
作者：
Riaz, Asif;Gandhiraman, Ram P.;Lee, Luke P.
我们报告的气相高反应性的化学物种的控制扩散到长的聚合物微腔，形成玻璃状的，低渗透性的微腔的内表面上的阻挡膜。在射频（RF）等离子体环境中，由O-2和六甲基二硅氧烷（HM DSO）的片段化产生的反应性物质被允许扩散到聚二甲基硅氧烷（PDMS）的微腔中，其中表面反应导致形成有效的玻璃状薄膜屏障。包括硅自由基和元素氧的反应性物种保持其反应性足够的时间（高达7000秒）和生存的随机扩散步行通过微腔形成玻璃屏障多达65毫米的腔入口。阻挡层厚度和生长长度可以通过反应时间和腔室操作压力来控制。增加腔入口的横截面积和/或减小平均自由程被发现增加阻挡膜的厚度。使用光发射光谱分析来表征从HMDSO形成的反应性片段，并且能量色散X射线分析显示屏障组合物与硅的氧化物（SiOx）一致。在PDMS微腔内部形成的玻璃屏障阻挡小分子如罗丹明B（Rh B）和生物素的渗透或吸收，并且还抵抗有机溶剂如甲苯的渗透，防止PDMS微流体结构溶胀和变形。此外，在PDMS微腔中形成玻璃状薄膜增强了电渗流（EDF）相对于未涂覆的PDMS装置的稳定性，其中电渗流不稳定性是显著的;这使得通过电泳分离具有可重复性（相对标准偏差3%，n = 5）和基线峰分辨率（R：1.3），与在常规熔融石英毛细管中获得的可比较。
We report the controlled diffusion of gas-phase high-reactivity chemical species into long polymeric microcavities to form glass-like, low-permeability barrier films on the interior surfaces of the microcavities. Reactive species created from fragmentation of O-2 and hexamethyldisiloxane (HM DSO) in a radio-frequency (RF) plasma environment are allowed to diffuse into the microcavities of polydimethylsiloxane (PDMS), where surface reactions lead to the formation of an effective, glass-like thin-film barrier. Reactive species including silicon radicals and elemental oxygen maintain their reactivity for sufficient times (up to 7000 s) and survive the random diffusional walk through the microcavities to form glass barriers as much as 65 mm from the cavity entrance. The barrier thickness and the growth length can be controlled by the reaction time and chamber operating pressure. Increasing the cross sectional area of the cavity inlet and/or decreasing the mean free path was found to increase the thickness of the barrier film. Optical emission spectroscopic analysis was used to characterize the reactive fragments formed from HMDSO, and energy-dispersive X-ray analysis revealed that the barrier composition is consistent with oxides of silicon (SiOx). Formed inside PDMS microcavities, the glass barrier blocks the penetration or absorption of small molecules such as rhodamine B (RhB) and biotin, and also resists permeation of organic solvents such as toluene, preventing the PDMS microfluidic structures from swelling and deforming. Moreover, formation of glass-like thin films in PDMS microcavities enhances the stability of electroosmotic flow (EDF) relative to uncoated PDMS devices, in which EOF instabilities are significant; this enables separation by electrophoresis with reproducibility (relative standard deviation 3%, n = 5) and baseline peak resolution (R:1.3) comparable to that obtained in conventional fused-silica capillaries.