• Title, Summary, Keyword: two-photon process

Search Result 82, Processing Time 0.03 seconds

Study on Process Parameters of a SU-8 Resin in Two-photon Streolithography for the Fabrication of Robust Three-dimensional Microstructures (SU-8 레진을 이용한 이광자 흡수 광조형 공정에서 고강성 3 차원 마이크로 형상 제작을 위한 공정 변수 분석)

  • Son, Yong;Lim, Tae-Woo;Yi, Shin-Wook;Kong, Hong-Jin;Park, Sang-Hu;Yang, Dong-Yol
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.25 no.1
    • /
    • pp.130-137
    • /
    • 2008
  • Two-photon stereolithography (TPS) is recognized as a useful process for the fabrication of three-dimensional microstructures. Recently, the need for a two-photon curable resin with high strength increases as 3-D moicrostructures of high aspect ratio or large scale of several hundreds micrometers are required for applications of nano/micro devices in IT/BT. In this work, process parameters of TPS employing the SU-8 which is a representative two-photon curable resin with high strength have been studied for the precise fabrication of 3-D microstructures with high strength. The pre-baking and post-baking processes are studied and the parameter study of the SU-8 in TPS is conducted. Through this work, very small roughness of 12 nm and the minimum aspect ratio of ${\sim}1$ which provides a precise accumulation of layers could be obtained. Using the conditions studied in this work, some 3-D examples are fabricated.

Development of Large-area Two-photon Stereolithography Process for the Fabrication of Large Three-dimensional Microstructures (대면적 3 차원 마이크로 형상제작을 위한 스테이지 스캐닝 시스템을 이용한 이광자 흡수 광조형 공정 개발)

  • Lim, Tae-Woo;Son, Yong;Yi, Shin-Wook;Kong, Hong-Jin;Park, Sang-Hu;Yang, Dong-Yol
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.25 no.1
    • /
    • pp.122-129
    • /
    • 2008
  • Two-photon stereolithography is recognized as a promising process for the fabrication of three-dimensional (3D) microstructures with 100 nm resolution. Generally, beam-scanning system has been used in the conventional process of two-photon stereolithography, which is limited to the fabrication of micro-prototypes in small area of several tens micrometers. For the applications to 3D high-functional micro-devices, the fabrication area of the process is required to be enlarged. In this paper, large-area two-photon stereolithography (L-TPS) employing stage scanning system has been developed. Continuous scanning method is suggested to improve the fabrication speed and parameter study is conducted. An objective lens of high numerical aperture (N.A.) and high strength material were employed in this system. Through this work, 3D microstructures of $600*600*100\;{\mu}m$ were fabricated.

Vibronically Induced Two-Photon Transitions in Benzene

  • Chung, Gyu-Sung;Lee, Duck-Kwan
    • Bulletin of the Korean Chemical Society
    • /
    • v.10 no.3
    • /
    • pp.298-302
    • /
    • 1989
  • The strengths of two-photon transitions from the ground state to excited vibronic states in benzene are calculated by using the CNDO/2-U wave functions. The role of vibronic coupling in two-photon absorption process is discussed. The $A_{1{\bar{g}}}-A_{2g}^+$ two-photon transitions, which are forbidden by the identity-forbidden selection rule in single frequency two-photon absorption, are too weak to be experimentally observed even when two photons of different energies are used. It is because the transitions are forbidden also by the pseudo-parity selection rule which are applicable for alternant hydrocarbons such as benzene. It is also shown that the vibronic coupling is not very effective in altering the pseudo-parity property of the electronic state. The strength of the vibronically induced two-photon absorption is strongly affected by the presence of an electronic state from which two-photon absorption can borrow the intensity. It is pointed out that the pseudo-parity selection rule may be violated in such cases.

  • PDF

Improvement of Metallic Micro-Structure Precision Employing Two-photon Induced Photoreduction Process (이광자 흡수 광환원 공정을 이용한 마이크로 금속형상 제작의 정밀화에 관한 연구)

  • Son, Yong;Lim, Tae-Woo;Yang, Dong-Yol;Prem, Prabhakaran;Lee, Kwang-Sup
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.32 no.9
    • /
    • pp.754-760
    • /
    • 2008
  • A two-photon induced photoreduction process suggests a possibility for fabricating complicated metallic microstructures which can be applied to 3-D micro-circuits and optical devices, etc. The process employs the photoreduction of silver ions in a metallic solution which is composed of metallic salt ($AgNO_3$) and watersoluble polymer ((poly(4-styrenesulfonique acid) 18wt. % in $H_2O$, $(C_8H_8O_3S)_n$)). In this process, the improvement of the resolution and the uniformity of fabricated metallic structures are important issues. To address these problems, continuous forming window (CFW) is obtained from a parametric study on the conditions of laser power and scanning velocity and the direct seed generation (DSG) method is proposed. Silver nano particles are uniformly generated in a metallic solution through the DSG method, which enables the decrease of a laser power to trigger the photoreduction of silver ions as well as the increase of metal contents in a metallic solution. So the two-photon induced photoreduction property of a metallic solution is improved. Through this work, precise silver patterns are fabricated with a minimum line width of 400 nm.

Fabrication of Precise Patterns using a Laser Beam Expanding Technique in Nano-Replication Printing (nRP) Process (레이저 빔 단면확대를 이용한 나노 복화(複畵)공정의 패턴 정밀도 향상에 관한 연구)

  • Park Sang Hu;Lim Tae Woo;Yang Dong-Yol;Yi Shin Wook;Kong Hong Jin
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.22 no.1
    • /
    • pp.175-182
    • /
    • 2005
  • A laser beam expanding technique is employed to fabricate precise nano-patterns in a nano-replication printing (nRP) process. In the nRP process, some patterns can be fabricated in the range of several microns inside on a polymerizable resin by using a volume-pixel (voxel) matrix that is transformed from a two-tone bitmap figure file. The liquid monomers are polymerized by means of a two-photon-absorption (TPA) phenomenon that is induced by a femtosecond (fs)-pulse laser. The yokels are generated consecutively to merge into adjoining yokels in the process of fabricating a pattern. The resolution of a fabricated pattern can be obtained under the diffraction limit of a laser beam by the two-photon absorbed polymerization (TPP). In this work, a beam-expanding technique has been applied to enlarge a working area and to fabricate precise patterns. Through this work, a working area is expanded by the technique as much as 2.5 times compared with a case of without a beam expanding technique, and precision of outside patterns is improved.

Optimization of Energy Modulation Filter for Dual Energy CBCT Using Geant4 Monte-Carlo Simulation

  • Ju, Eun Bin;Ahn, So Hyun;Choi, Sang Gyu;Lee, Rena
    • Progress in Medical Physics
    • /
    • v.27 no.3
    • /
    • pp.125-130
    • /
    • 2016
  • Dual energy computed tomography (DECT) is used to classify two materials and quantify the mass density of each material in the human body. An energy modulation filter based DECT could acquire two images, which are generated by the low- and high-energy photon spectra, in one scan, with one tube and detector. In the case of DECT using the energy modulation filter, the filter should perform the optimization process for the type of materials and thicknesses for generating two photon spectra. In this study, Geant4 Monte-Carlo simulation toolkit was used to execute the optimization process for determining the property of the energy modulation filter. In the process, various materials used for the energy modulation filter are copper (Cu, $8.96g/cm^3$), niobium (Nb, $8.57g/cm^3$), stannum (Sn, $7.31g/cm^3$), gold (Au, $19.32g/cm^3$), and lead (Pb, $11.34g/cm^3$). The thickness of the modulation filter varied from 0.1 mm to 1.0 mm. To evaluate the overlap region of the low- and high-energy spectrum, Geant4 Monte-Carlo simulation is used. The variation of the photon flux and the mean energy of photon spectrum that passes through the energy modulation filter are evaluated. In the primary photon spectrum of 80 kVp, the optimal modulation filter is a 0.1 mm lead filter that can acquire the same mean energy of 140 kVp photon spectrum. The lead filter of 0.1 mm based dual energy CBCT is required to increase the tube current 4.37 times than the original tube current owing to the 77.1% attenuation in the filter.

High-speed Two-photon Laser Scanning Microscopy Imaging of in vivo Blood Cells in Rapid Circulation at Velocities of Up to 1.2 Millimeters per Second

  • Boutilier, Richard M.;Park, Jae Sung;Lee, Ho
    • Current Optics and Photonics
    • /
    • v.2 no.6
    • /
    • pp.595-605
    • /
    • 2018
  • The two-photon process of microscopy provides good spatial resolution and optical sectioning ability when observing quasi-static endogenous fluorescent tissue within an in vivo animal model skin. In order to extend the use of such systems, we developed a two-photon laser scanning microscopy system capable of also capturing $512{\times}512$ pixel images at 90 frames per second. This was made possible by incorporating a 72 facet polygon mirror which was mounted on a 55 kRPM motor to enhance the fast-scan axis speed in the horizontal direction. Using the enhanced temporal resolution of our high-speed two-photon laser scanning microscope, we show that rapid processes, such as fluorescently labeled erythrocytes moving in mouse blood flow at up to 1.2 mm/s, can be achieved.

Enhancing Photon Utilization Efficiency for Astaxanthin Production from Haematococcus lacustris Using a Split-Column Photobioreactor

  • Kim, Z-Hun;Park, Hanwool;Lee, Ho-Sang;Lee, Choul-Gyun
    • Journal of Microbiology and Biotechnology
    • /
    • v.26 no.7
    • /
    • pp.1285-1289
    • /
    • 2016
  • A split-column photobioreactor (SC-PBR), consisting of two bubble columns with different sizes, was developed to enhance the photon utilization efficiency in an astaxanthin production process from Haematococcus lacustris. Among the two columns, only the smaller column of SC-PBR was illuminated. Astaxanthin productivities and photon efficiencies of the SC-PBRs were compared with a standard bubble-column PBR (BC-PBR). Astaxanthin productivity of SC-PBR was improved by 28%, and the photon utilization efficiencies were 28-366% higher than the original BC-PBR. The results clearly show that the effective light regime of SC-PBR could enhance the production of astaxanthin.

Fabrication of Three-Dimensional Micro-Shell Structures Using Two-Photon Polymerization (이광자 흡수 광중합에 의한 3차원 마이크로 쉘 구조물 제작)

  • Park Sang Hu;Lim Tae Woo;Yang Dong-Yol
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.29 no.7
    • /
    • pp.998-1004
    • /
    • 2005
  • A nano-stereolithography (NSL) process has been developed for fabrication of 3D shell structures which can be applied to various nano/micro-fluidic devices. By the process, a complicated 3D shell structure on a scale of several microns can be fabricated using lamination of layers with a resolution of 150 nm in size, so it does not require the use of my sacrificial layer or any supporting structure. A layer was fabricated by means of solidifying liquid-state monomers using two-photon absorption (TPA) induced using a femtosecond laser processing. When the polymerization process is finished, unsolidified liquid state resins can be removed easily by dropping several droplets of ethanol fur developing the fabricated structure. Through this work, some 3D shell structures, which can be applied to various applications such as nano/micro-fluidic devices and MEMS system, were fabricated using the developed process.