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Gang, Myeong Gu,Chae, Ki Woon,Kim, Wook-Bae,Jung, Young Hun,Jun, Martin B.G.,Min, Byung-Kwon Elsevier 2019 Journal of manufacturing processes Vol.37 No.-
<P><B>Abstract</B></P> <P>Microchannels must have appropriate physical (e.g., shape, size and surface roughness) and chemical (e.g., functional groups and wettability) properties to be used in microfluidic devices. In general, microchannels, which are made of polymeric materials, are produced through a molding process and chemically treated to have proper wettability. However, mold fabrication and chemical treatment require a significant amount of time and cost. In this study, we used a micromilling process to fabricate a microchannel on polymer material. The contact angle on the machined surface was changed according to the wettability model by varying the surface roughness controlled by cutting parameters. By mechanical cutting of the naturally hydrophobic polymer, the contact angle could be physically changed from 76° to 109° by changing cutting parameters without any chemical change.</P>
Material interface detection based on secondary electron images for focused ion beam machining
Joe, Hang-Eun,Lee, Won-Sup,Jun, Martin B. G.,Park, No-Cheol,Min, Byung-Kwon Elsevier 2018 Ultramicroscopy Vol.184 No.2
<P><B>Abstract</B></P> <P>A method for interface detection is proposed for focused ion beam (FIB) processes of multilayered targets. As multilayers have emerged as promising structures for nanodevices, the FIB machining of multilayers has become a challenging issue. We proposed material interface detection by monitoring secondary electron (SE) images captured during the FIB process. The average of the gray-levels and the skewness coefficient of gray-level histograms of the SE images were evaluated to recognize endpoints for the FIB processes. The FIB process control with the proposed method was demonstrated by fabricating the nanostructures on the multilayered target without thickness information. It was also demonstrated on a curved surface. Grooves with a desired depth into the target and an aperture as an opening window were precisely fabricated by the FIB process control. The proposed strategy of the FIB process can be used for complex substrates such as curved or flexible targets.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A strategy of material interface detection was proposed for FIB process control. </LI> <LI> Gray-levels of ion-induced secondary electron images were monitored to analyze the surface characteristics of the ion-sputtered area. </LI> <LI> Peaks on the graph of average and skewness coefficient of gray-levels was analyzed to detect the interlayer interface as endpoints for the FIB process. </LI> <LI> The proposed strategy was verified by fabrication of nanostructures on flat and curved substrates of the multilayered target with high precision. </LI> </UL> </P>
Formation mechanism of self-organized nano-ripples on quartz surface using femtosecond laser pulses
Ahsan, Md. Shamim,Lee, Man Seop,Hasan, Mohammad Khairul,Noh, Young-Chul,Sohn, Ik-Bu,Ahmed, Farid,Jun, Martin B.G. Elsevier 2015 OPTIK -STUTTGART- Vol.126 No.24
<P><B>Abstract</B></P> <P>This article demonstrates the formation of self-organized nano-ripples on a quartz surface by irradiation of femtosecond laser pulses. Self-oriented nano-ripples are printed on the quartz surface by controlling various laser parameters: average pulse energy, pulse width, and number of laser pulses on each irradiated spot. We validate that the direction of the self-organized nano-ripples are oriented perpendicularly to the laser polarization direction. We also investigate and analyze the dependency of nano-ripples period on various laser parameters including the pulse energy, number of laser pulses, and pulse width. The nano-ripples show increasing trend with the increase of laser energy and pulse width, whereas show decreasing trend with the increase of irradiated laser pulses. We also explain, qualitatively, the formation mechanism of the self-organized nano-ripples on quartz surface.</P>
Elgnemi, Tarek,Ahmadi, Keivan,Songmene, Victor,Nam, Jungsoo,Jun, Martin B.G. Elsevier 2017 Journal of manufacturing processes Vol.30 No.-
<P><B>Abstract</B></P> <P>Carbon Fiber Reinforced Polymers (CFRP) are considered hard to cut materials, because of the abrasiveness of carbon fibers and the low transverse strength of the composite layers that leads to delimitation under machining forces. The application of cutting fluid is a common way of reducing tool wear and machining forces in machining of metallic materials, yet this solution cannot be applied in machining of CFRP, because moisture damages the structural integrity of the composite workpiece. In this paper, an experimental study is conducted to examine the feasibility and effectiveness of applying atomized cutting fluid in milling of CFRP. In the studied atomization-based method, the cutting fluid is broken down into micrometer size droplets that are sprayed directly into the cutting zone. In the presented study, two types of cutting fluids, general purpose semisynthetic coolant and vegetable oil, are applied by atomization, and their performances in reducing cutting forces, tool wear, surface roughness, and delamination are studied over a range of cutting speeds and feed rate values.</P>