Variation in diffusion of gases through PDMS due to plasma surface treatment and storage conditions
Variation in diffusion of gases through PDMS due to plasma surface treatment and storage conditions
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DOI：
10.1007/s10544-013-9808-2
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发表时间：
2014-02-01
影响因子：
2.8
通讯作者：
McCawley, Lisa J.
中科院分区：
文献类型：
--
作者：
Markov, Dmitry A.;Lillie, Elizabeth M.;McCawley, Lisa J.
聚二甲基硅氧烷（PDMS）是微流体器件制造中常用的聚合物，这是由于诸如透明性、透气性和易于用软光刻进行图案化的特征。PDMS的表面特性也可以很容易地用氧气或低压空气等离子体将其从疏水状态转化为亲水状态来改变。作为这种转化的一部分，表面甲基被去除并被羟基取代，使暴露的表面类似于二氧化硅，一种不透气的物质。我们已经利用铂（II）-四（五氟苯基）卟啉固定在一个薄（类似于1.5 μ m厚）聚苯乙烯矩阵作为氧传感器，斯特恩-沃尔默关系，和菲克的简单扩散定律来测量的PDMS组合物，治疗，和存储对氧气扩散通过PDMS的影响。结果表明，新鲜氧化的PDMS表现出显着较小的扩散系数，表明在PDMS表面上形成的SiO2层产生了阻碍屏障。这种屏障在空气中储存3天后消失，但如果PDMS与水保持接触，则在长达3周的时间内仍然显著。此外，较高密度的PDMS制剂（5：1比率）显示出与正常（10：1比率）制剂相似的扩散特性，但在等离子体处理后显示出60%更小的扩散系数，即使在空气中储存3周后也从未恢复到处理前水平。了解等离子体表面处理如何有助于氧扩散将有助于利用PDMS的气体渗透性，以在微流体生物反应器系统内建立限定的常氧和低氧条件。
Polydimethylsiloxane (PDMS) is a commonly used polymer in the fabrication of microfluidic devices due to such features as transparency, gas permeability, and ease of patterning with soft lithography. The surface characteristics of PDMS can also be easily changed with oxygen or low pressure air plasma converting it from a hydrophobic to a hydrophilic state. As part of such a transformation, surface methyl groups are removed and replaced with hydroxyl groups making the exposed surface to resemble silica, a gas impermeable substance. We have utilized Platinum(II)-tetrakis(pentaflourophenyl)porphyrin immobilized within a thin (similar to 1.5 um thick) polystyrene matrix as an oxygen sensor, Stern-Volmer relationship, and Fick's Law of simple diffusion to measure the effects of PDMS composition, treatment, and storage on oxygen diffusion through PDMS. Results indicate that freshly oxidized PDMS showed a significantly smaller diffusion coefficient, indicating that the SiO2 layer formed on the PDMS surface created an impeding barrier. This barrier disappeared after a 3-day storage in air, but remained significant for up to 3 weeks if PDMS was maintained in contact with water. Additionally, higher density PDMS formulation (5:1 ratio) showed similar diffusion characteristics as normal (10:1 ratio) formulation, but showed 60 % smaller diffusion coefficient after plasma treatment that never recovered to pre-treatment levels even after a 3-week storage in air. Understanding how plasma surface treatments contribute to oxygen diffusion will be useful in exploiting the gas permeability of PDMS to establish defined normoxic and hypoxic oxygen conditions within microfluidic bioreactor systems.