• Title, Summary, Keyword: SU-8 Photoresist

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Effect of structural voids on mesoscale mechanics of epoxy-based materials

  • Tam, Lik-ho;Lau, Denvid
    • Coupled systems mechanics
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    • v.5 no.4
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    • pp.355-369
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    • 2016
  • Changes in chemical structure have profound effects on the physical properties of epoxy-based materials, and eventually affect the durability of the entire system. Microscopic structural voids generally existing in the epoxy cross-linked networks have a detrimental influence on the epoxy mechanical properties, but the relation remains elusive, which is hindered by the complex structure of epoxy-based materials. In this paper, we investigate the effect of structural voids on the epoxy-based materials by using our developed mesoscale model equipped with the concept of multiscale modeling, and SU-8 photoresist is used as a representative of epoxy-based materials. Developed from the results of full atomistic simulations, the mesoscopic model is validated against experimental measurements, which is suitable to describe the elastic deformation of epoxy-based materials over several orders of magnitude in time- and length scales. After that, a certain quantity of the structure voids is incorporated in the mesoscale model. It is found that the existence of structural voids reduces the tensile stiffness of the mesoscale epoxy network, when compared with the case without any voids in the model. In addition, it is noticed that a certain number of the structural voids have an insignificant effect on the epoxy elastic properties, and the mesoscale model containing structural voids is close to those found in real systems.

Design and Fabrication of Mold Insert for Injection Molding of Microfluidic tab-on-a-chip for Detection of Agglutination (응집반응 검출을 위한 미세 유체 Lab on a chip의 사출성형 금형 인서트의 디자인 및 제작)

  • Choi, Sung-Hwan;Kim, Dong-Sung;Kwon, Tai-Hun
    • Transactions of Materials Processing
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    • v.15 no.9
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    • pp.667-672
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    • 2006
  • Agglutination is one of the most commonly employed reactions in clinical diagnosis. In this paper, we have designed and fabricated nickel mold insert for injection molding of a microfluidic lab-on-a-chip for the purpose of the efficient detection of agglutination. In the presented microfluidic lab-on-a-chip, two inlets for sample blood and reagent, flow guiding microchannels, improved serpentine laminating micromixer(ISLM) and reaction microwells are fully integrated. The ISLM, recently developed by our group, can highly improve mixing of the sample blood and reagent in the microchannel, thereby enhancing reaction of agglutinogens and agglutinins. The reaction microwell was designed to contain large volume of about $25{\mu}l$ of the mixture of sample blood and reagent. The result of agglutination in the reaction microwell could be determined by means of the level of the light transmission. To achieve the cost-effectiveness, the microfluidic lab-on-a-chip was realized by the injection molding of COC(cyclic olefin copolymer) and thermal bonding of two injection molded COC substrates. To define microfeatures in the microfluidic lab-on-a-chip precisely, the nickel mold inserts of lab-on-a-chip for the injection molding were fabricated by combining the UV photolithography with a negative photoresist SU-8 and the nickel electroplating process. The microfluidic lab-on-a-chip developed in this study could be applied to various clinical diagnosis based on agglutination.

Fabrication of Two-dimensional MoS2 Films-based Field Effect Transistor for High Mobility Electronic Device Application

  • Joung, DaeHwa;Park, Hyeji;Mun, Jihun;Park, Jonghoo;Kang, Sang-Woo;Kim, TaeWan
    • Applied Science and Convergence Technology
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    • v.26 no.5
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    • pp.110-113
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    • 2017
  • The two-dimensional layered $MoS_2$ has high mobility and excellent optical properties, and there has been much research on the methods for using this for next generation electronics. $MoS_2$ is similar to graphene in that there is comparatively weak bonding through Van der Waals covalent bonding in the substrate-$MoS_2$ and $MoS_2-MoS_2$ heteromaterial as well in the layer-by-layer structure. So, on the monatomic level, $MoS_2$ can easily be exfoliated physically or chemically. During the $MoS_2$ field-effect transistor fabrication process of photolithography, when using water, the water infiltrates into the substrate-$MoS_2$ gap, and leads to the problem of a rapid decline in the material's yield. To solve this problem, an epoxy-based, as opposed to a water-based photoresist, was used in the photolithography process. In this research, a hydrophobic $MoS_2$ field effect transistor (FET) was fabricated on a hydrophilic $SiO_2$ substrate via chemical vapor deposition CVD. To solve the problem of $MoS_2$ exfoliation that occurs in water-based photolithography, a PPMA sacrificial layer and SU-8 2002 were used, and a $MoS_2$ film FET was successfully created. To minimize Ohmic contact resistance, rapid thermal annealing was used, and then electronic properties were measured.

Bragg Reflecting Waveguide Device Fabricated on a Flexible Substrate using a Nano-imprinting Technology (나노임프린팅 기술을 이용한 유연성 브래그 반사 광도파로 소자)

  • Kim, Kyung-Jo;Yi, Jeong-Ah;Oh, Min-Cheol
    • Korean Journal of Optics and Photonics
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    • v.18 no.2
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    • pp.149-154
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    • 2007
  • Bragg reflecting waveguide devices have been fabricated on a flexible polymer substrate utilizing a post lift-off process which could Provide excellent uniformity of grating Patterns on Plastic film. The 510 m Period Bragg grating pattern is made by two methods. In the first sample the grating is fabricated by exposing the laser interference pattern on a photoresist, and then it is inscribed by $O_2$ plasma etching. The grating pattern of the second sample is formed by a PDMS soft mold imprinting process. The selective adhesion property of SU-8 material for Au and Si surfaces is utilized to prepare a 100-mm thick plastic substrate. Single mode waveguide is fabricated on the plastic substrate using polymer materials with refractive indices of 1.540 and 1.430 for the core and the cladding layers, respectively. The Bragg grating on Plastic substrate does not show any degradation in its spectral response compared to the reference sample made on a silicon wafer.

Variation of Flow Rates in Heterogeneous Microchannel Systems (비균일계 마이크로채널에서의 유량 변화 특성)

  • Kim, Jin-Yong;Lee, Hyo-Song;Yu, Jae-Keun;Kim, Ki-Ho;Rhee, Young Woo
    • Applied Chemistry for Engineering
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    • v.17 no.1
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    • pp.28-32
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    • 2006
  • This study investigated the variation of flow rates in microchannels that consisted of polydimethyl siloxane (PDMS) and glass using various external voltages. Three different microchannel widths and two different depths. PDMS and negative photoresist (SU-8) were used to make the microchannels by the soft lithographic method. For each depth of microchannel ($50{\mu}m$ and $100{\mu}m$), three different widths ($100{\mu}m$, $200{\mu}m$ and $300{\mu}m$) were made. In each case, several different external voltages were applied (0.3 kV, 0.35 kV, 0.4 kV and 0.45 kV) to examine the flow rates. Our results indicated that flow rate increased with an increase of the external voltage at the same microchannel width. This was because the electrical field was increased as the external voltage increased. For the same external voltage, the flow rate increased as the microchannel's width increased. These results showed that the resistance in the microchannel decreased as the microchannel's width increased. Also, to investigate the effect of microchannel's depth and width, the cross-sectional area of the microchannel was increased to the double in area. As a result, the effect of the microchannel's depth was higher at a low external voltage, and the effect of the microchannel's width was higher at a high external voltage.

Effect of Contact Angles of PDMS and External Voltage on Flow Velocity in Microchannel (PDMS의 접촉각 및 외부전압 변화에 따른 마이크로채널에서 유체의 속도변화)

  • Lee, Hyo-Song;Kim, Jin-Yong;Kim, Jeong-Soo;Rhee, Young Woo
    • Korean Chemical Engineering Research
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    • v.43 no.1
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    • pp.92-97
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    • 2005
  • In this study, the effect of contact angles of PDMS and external voltage has been investigated. SU-8 (Microchem, USA) negative photoresist and PDMS are used to make the microchannel. The contact angle of the native PDMS is $105^{\circ}$. The native PDMS is treated with the oxygen plasma and the contact angle changes $19^{\circ}$, $46^{\circ}$ and $69^{\circ}$. As a result, the rate of increase in flow velocity is not directly proportional to the rate of increase of external voltage. This is because the electrical double layer is condensed and the zeta potential is increased with an increase of the external voltage. The flow velocity is highest for the contact angle of $19^{\circ}$ at the same external voltage. Hence we conclude that the thickness of electrical double layer and flow velocities vary with contact angle at the same external voltage.