• Proceedings of the Korean Society of Laser Processing Conference
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• 2006.11a
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• pp.96-102
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• 2006

In this study, manufacturing of polymer master, PDMS(poly dimethylsiloxane) transfer mold, and mold insert was investigated for laser LIGA(LIthography Calvanoformung Abformtechnik). Initially, ablation by excimer laser radiation was used successfully to make 3-D microstructure of PET. After then, the PDMS transfer mold was replicated using ablated PET. Finally, epoxy resin tooling on replicated PDMS transfer mold was executed for making mold insert. From these facts we can conclude that excimer laser ablation of polymer and fabricaiton of PDMS transfer mold are reasonable tools to substitute for X-ray lithography of LIGA process in microstructuring.

• Textile Coloration and Finishing
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• v.20 no.1
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• pp.8-15
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• 2008

We presented the modified decal-transfer lithography (DTL) and light stamping lithography (LSL) as new powerful methods to generate patterns of poly(dimethylsiloxane) (PDMS) on the substrate. The microstructures of PDMS fabricated by covalent binding between PDMS and substrate had played as barrier to locally control wettability. The transfer mechanism of PDMS is cohesive mechanical failure (CMF) in DTL method. In the LSL method, the features of patterned PDMS are physically torn and transferred onto a substrate via UV-induced surface reaction that results in bonding between PDMS and substrate. Additionally we have exploited to generate the patterning of rhodamine B and quantum dots (QDs), which was accomplished by hydrophobic interaction between dyes and PDMS micropatterns. The topological analysis of micropatterning of PDMS were performed by atomic force microscopy (AFM), and the patterning of rhodamine B and quantum dots was clearly shown by optical and fluorescence microscope. Furthermore, it could be applied to surface guided flow patterns in microfluidic device because of control of surface wettability. The advantages of these methods are simple process, rapid transfer of PDMS, modulation of surface wettability, and control of various pattern size and shape. It may be applied to the fabrication of chemical sensor, display units, and microfluidic devices.

• Membrane Journal
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• v.18 no.3
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• pp.219-225
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• 2008

In this research, polydimethylsiloxane-polymethylmethacrylate (PDMS-PMMA) block copolymer was synthesized from polydimethylsiloxane (PDMS) and methylmethacrylate (MMA) monomer using atom transfer radical polymerization (ATRP). The synthesis characterization of the PDMS-b-PMMA copolymer membrane was carried out by a FT-IR, $^1H$-NMR, GPC and DSC. The permeabilities of nitrogen and hydrogen gases were observed being $1.2{\sim}l.5$ barrer and $6.2{\sim}10.5$ barrer, respectively. Simultaneously, selectivities of hydrogen against nitrogen were $5.3{\sim}6.9$. The permeability and selectivity of PDMS-b-PMMA copolymer membrane were showed lower than the PDMS membrane, but higher than the PMMA membrane.

• Korean Journal of Materials Research
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• v.19 no.8
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• pp.437-442
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• 2009

This paper describes an improved strategy for controlling the adhesion force using both the antiadhesion and adhesion layers for a successful large-area transfer process. An MPTMS (3-mercaptopropyltrimethoxysilane) monolayer as an adhesion layer for Au/Pd thin films was deposited on Si substrates by vapor self assembly monolayer (VSAM) method. Contact angle, surface energy, film thickness, friction force, and roughness were considered for finding the optimized conditions. The sputtered Au/Pd ($\sim$17 nm) layer on the PDMS stamp without the anti-adhesion layer showed poor transfer results due to the high adhesion between sputtered Au/Pd and PDMS. In order to reduce the adhesion between Au/Pd and PDMS, an anti-adhesion monolayer was coated on the PDMS stamp using FOTS (perfluorooctyltrichlorosilane) after $O_2$ plasma treatment. The transfer process with the anti-adhesion layer gave good transfer results over a large area (20 mm $\times$ 20 mm) without pattern loss or distortion. To investigate the applied pressure effect, the PDMS stamp was sandwiched after 90$^{\circ}$ rotation on the MPTMS-coated patterned Si substrate with 1-${\mu}m$ depth. The sputtered Au/Pd was transferred onto the contact area, making square metal patterns on the top of the patterned Si structures. Applying low pressure helped to remove voids and to make conformal contact; however, high pressure yielded irregular transfer results due to PDMS stamp deformation. One of key parameters to success of this transfer process is the controllability of the adhesion force between the stamp and the target substrate. This technique offers high reliability during the transfer process, which suggests a potential building method for future functional structures.

• Journal of the Korean Applied Science and Technology
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• v.32 no.2
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• pp.232-239
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• 2015

In this paper, we study the dry transfer technology utilizing PDMS (Polydimethylsiloxane) stamp of a large single-layer graphene grown on Cu-foil as catalytic metal by using Chemical Vapor Deposition (CVD). By changing the surface property of the target substrate through $UV/O_3$ treatment, we can transfer the graphene on the target substrate while minimizing mechanical damages of graphene layer. Multi-layer (1~4 layers) graphene was stacked on $SiO_2/Si$ wafer successfully by repeating thetransfer method/process and then optical transmittance and sheet resistance of graphene layers have been measured as a quality assessment.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.719-720
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• 2010

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.121-127
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• 2022

Micro-LED is a light-emitting diode smaller than 100 ㎛ in size. It attracts much attention due to its superior performance, such as resolution, brightness, etc., and is considered for various applications like flexible display and VR/AR. Micro-LED display requires a mass transfer process to move micro-LED chips from a LED wafer to a target substrate. In this study, we proposed a vacuum chuck method as a mass transfer technique. The vacuum chuck was fabricated with MEMS technology and PDMS micro-mold process. The spin-coating approach using a dam structure successfully controlled the PDMS mold's thickness. The vacuum test using solder balls instead of micro-LED confirmed the vacuum chuck method as a mass transfer technique.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.43.1-43.1
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• 2018

Spatial distribution of binding state in depth direction is investigated in a hard skin layer on soft polydimethylsiloxane (PDMS) fabricated by Ar ion beam irradiations. The hard skin layer known as a silica-like homogenous layer was composed of two layers. Impinging Ar ions transfer energy to PDMS as a function of collisional energy transfer rate, which is the maximum at surface and decreases gradually as an ion penetrates. This formed the heterogeneous hard skin layer that consists of a top-most layer and an intermediate layer. XPS depth profiling showed the existence of the top-most layer and intermediate layer. In the top-most layer, scission and cross-linking were occurred simultaneously and Si-O bond showed dissociated status, SiOx (x = 1.25 - 1.5). Under the top-most layer, there was the intermediate layer in which cross-linking is mainly occurred and Si-O bond showed silica-like binding status, SiOx (x = 1.75 - 2). And theoretical analysis which calculates the collisional energy transfer and a displacement per atom explained the thickness variation of top-most layer according to Ar ion energy from 360 eV to 840 eV.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.40-43
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• 2004

Stamps for microcontact processing are fabricated by casting elastomer such as PDMS on a master with a negative of the desired pattern. After curing, the PDMS stamp is peeled away from the master and exposed to a solution of ink and then dried. Transfer of the ink from the PDMS stamp to the substrate occurs during a brief contact between stamp and substrate. Generally, negative-tone masters, which are used for making positive-tone PDMS stamps, are fabricated by using photolithographic technique. The shortcomings of photolithography are a relative high-cost process and require extensive processing time and heavy capital investment to build and maintain the fabrication facilities. The goal of this study is to fabricate a negative-tone master by using Nano-indenter based patterning technique. Various sizes of V-grooves and U-groove were fabricated by using the combination of nanoscratch and HF isotropic etching technique. An achieved negative-tone structure was used as a master in the PDMS replica molding process to fabricate a positive-tone PDMS stamp.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.3
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• pp.406-412
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• 2018

This paper describes the fabrication process of laser induced graphene (LIG) and its transfer method on to a flexible and stretchable PDMS substrate. By irradiating CO2 laser on a polyimide(PI) film surface, a localized high temperature is created, resulting in a three-dimensional porous graphene network structure with good conductivity. This LIG electrode is relatively easy to fabricate and since it is very weak the LIG electrode was transferred to a flexible PDMS substrate to increase the sturdiness as well as possible use in flexible applications. Sheet resistance, thickness, and electrochemical activity of the fabricated in-situ LIG electrodes have been examined and compared with the LIG electrodes after transferring to PDMS elastomer. The properties of the LIG electrodes were also examined depending on the $CO_2$ laser power. As the irradiated laser power increased, the LIG electrode resistance decreases and the LIG electrode thickness increased. At 4.8 W of laser power, the average sheet resistance and thickness of the fabricated LIG electrodes were approximately $31.7{\Omega}/{\Box}$ and $62.67{\mu}m$, respectively. Moreover, the electrochemical activity of the fabricated LIG electrode at 4.8 W of laser power showed a high oxidation current of $28.2{\mu}A$ after transferring to PDMS.