Study of the Surface Treatment of a Capillary Inner-Wall using RF excited Microplasmas

研制了一种射频激发微等离子体产生系统，该系统在1 mm厚、2 cm见方的石英芯片上，以小于10 W的低功率，在横截面为150×500 μm^2的毛细管中产生常压He和Ar微等离子体。这是一个重量约5公斤的便携式等离子体源。利用光学发射光谱估计He和Ar等离子体的原子激发温度分别为2000-2500 K和5000 K。将微等离子体应用于内径φ0.5 mm的聚对苯二甲酸乙酯（PET）毛细管的内壁改性和SiO_2薄膜涂层，以验证电渗透流动（EOF）的控制。此外，微等离子体还应用于φ1×0.5 mm聚四氟乙烯（PTFE）管的内壁处理，以产生润湿性。当气体流速为200 ml/min，处理时间为15 s时，获得最大润湿性。等离子体处理后PTFE内壁的x射线光谱（XPS）显示出一个O1s峰，对应于C=0基团。扫描电镜（SEM）图像显示，等离子体处理后的内壁由于蚀刻效应而变得光滑。此外，还利用外径小于0.5 mm的钢制手术针，研制了常压微等离子体射流（μ-PJ）。应用O_2 μ-PJ对光刻胶薄膜进行局部去除。采用He/SF_6/O_2 μ-PJ对Si进行了局部刻蚀，刻蚀速率达到170 μm/min。

RF excited microplasma generation system, which generates atmospheric-pressure He and Ar microplasma in a capillary with a cross section of 150×500 μm^2 on a quartz chip 2 cm square of a thickness of 1 mm at a low-power of less than 10 W, has been developed. It's a portable plasma source with a weight of about 5 kg. The atomic excitation temperature of He and Ar plasmas were estimated by an optical emission spectroscopic to be 2000-2500 K and 5000 K, respectively. The microplasma was applied to inner-wall modification and SiO_2 thin films coating on a poly(ethylene terephthalate) (PET) capillary with an inner diameter of φ0.5 mm to demonstrate the electro-osmosis flow (EOF) control. Furthermore, the microplasma was also applied to inner-wall treatment of a poly(tetrafluoroethylene) (PTFE) tube of φ1×0.5 mm to cause the wettability. The maximum wettability was obtained at a gas flow rate of 200 ml/min and a treatment time of 15 s. X-ray spectroscopy (XPS) of the plasma treated PTFE inner-wall revealed an O1s peak corresponding to the C=0 group. Scanning electron microscope (SEM) image showed that the plasma treated inner-wall is smoothed due to the etching effect.Moreover, an atmospheric-pressure microplasma jet (μ-PJ) using a steel surgical needle with an outer diameter of less than 0.5 mm has been developed. The O_2 μ-PJ was applied a localized removal of a photoresist films. Furthermore, the localized Si etching was also examined using the He/SF_6/O_2 μ-PJ and the etching rate of 170 μm/min was attained.