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Direct laser writing of birefringent photonic crystals for the infrared spectral range
摘要： Infrared optical photonic crystals fabricated using direct laser writing, which is based on the two-photon polymerization of suitable monomers, have received substantial interest since the emergence of this process. Two-photon polymerization could be a disruptive technology for the fabrication of all-dielectric photonic crystals in the infrared spectral range, as it allows the synthesis of large scale arrays of uniform structures with arbitrary geometries and arrangements. However, all-dielectric photonic crystals that provide birefringent optical responses in the infrared spectral range have not yet been demonstrated using direct laser writing techniques. Here, the authors explore the form birefringence observed in photonic crystals composed of arrays of subwavelength-sized slanted polymer microwires. The photonic crystals investigated here were fabricated in a single fabrication step using direct laser writing of an infrared transparent photoresist (IP-Dip). A strong contrast of the cross-polarized re?ectance of photonic crystals as a function of the in-plane orientation is observed in the mid-infrared spectral range at λ ≈ 6:5 μm. This observation is indicative of an anisotropic optical behavior. Finite element based techniques corroborate the experimentally observed responses qualitatively.
关键词： two-photon polymerization,direct laser writing,infrared spectral range,birefringent photonic crystals,all-dielectric photonic crystals
更新于2025-11-14 15:18:02
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Systematic λ/21 resolution achieved in nanofabrication by two-photon-absorption induced polymerization
摘要： Photopolymerization, based on two-photon absorption in resins, has been recognized as one of the enabling technologies to fabricate three-dimensional micro/nanostructures with a sub-diffraction-limit resolution. This work focuses on improving the spatial resolution using femtosecond laser, λ=780 nm, with a systematic nanofabrication process which we developed. We discuss the factors influencing the spatial resolution, including the laser intensity, the exposure time, and the scanning speed by fabricating polymerized-voxels, nano-lines, and suspended nano-fibers in a photoresist based on a methyl-methacrylate monomer. We show that a resolution of ~36 nm, corresponding to ~λ/21, is achieved. Stable 3D microstructures can be fabricated by using our custom made set up.
关键词： Voxel,Resolution,Two Photon Polymerization,Micro/Nanostructures,Femtosecond Laser,Suspended Polymerized Fibers
更新于2025-09-23 15:22:29
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Modeling and analysis for the position and posture errors of laser focal spot in large-scale fabrication via two photon polymerization
摘要： The position and posture errors of laser focal spot significantly affect the fabrication quality and functionality of microstructures in two photon polymerization, especially over a large area. These errors can be greatly reduced by using ultra-precision positioning device, such as piezoelectric stage and scanning galvanometer. However, the position and posture errors cannot be neglected in large-scale fabrication using large stroke linear stages which are necessary tools in most instances. In the present work, the relationship between the geometric errors of large stroke positioning platform and the position and posture of laser focal spot were revealed and modeled by homogeneous transformation matrix. Key errors affecting on the position and posture of focal spot were found out by sensitivity analysis and compensated during the construction of machine tool. Proof-of-concept experiments were performed in a millimeter-level (1 mm × 1 mm) fabrication of microfluidic whose surface was measured by an optical profiler. The measuring results showed that arithmetical mean height (Sa) and root mean square height (Sq) of the measured surface were less than 100 nm and maximum height (Sz) of the measured surface was less than 500 nm. The compensated machine tool demonstrated a high precise performance within a large continuous area. This work was expected to provide references for the rational layout of optical components in optical system or error compensation in laser process equipment over a large area.
关键词： Laser beam delivery,Position and posture error,Error analysis,Large-scale fabrication,Two photon polymerization
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Increasing Two-Photon Polymerization Fabrication Speed of 3D Structures for Cell Interaction Studies
摘要： Expanding cell studies and tissue engineering from a 2D platform to a 3D mimic of their natural environment demands fabrication methods capable of creating scaffolds covering large volumes with feature sizes down to a few μm. Two-photon polymerization (TPP) is a direct writing method capable of fabricating free-form 3D structures with sub-wavelength features and is therefore well-suited for template fabrication for cell motility and tissue engineering. We demonstrate 9 times increased fabrication speed for 3D periodic structures using a diffractive optical element (DOE) that creates 9 beamlets from one femtosecond laser beam. The parallelized method maintains fabrication quality and each beamlet is used for the fabrication of the base structures that form the periodic pattern. Two 3D designs were fabricated from bio-compatible SZ2080 polymer, where the distance between structures are accurately matching the distance between beamlets. Both of the fabricated structure arrays consists of 3x3 patterns with 9 individual structures in each pattern and covers an area of 450x450 μm. The first design contains unsupported interconnections between individual structures and field-of-views (FOV’s). The second design contains additional supporting structures that stabilize those interconnections between individual structures and FOV’s. For the first design high similarity is observed between the individual base structures inside each FOV, while at the stitching positions between different FOV’s discrepancies are observed leading to gaps in the overall periodic pattern. The gaps arise from contraction of the polymer material during the development process and subsequently drying process. It is related to large leapfrog movement of the stage system (>150 μm) between FOV’s. In the second design, additional support was added between individual one voxel thin structures to overcome this problem. Using this strategy, no gaps are observed and any remaining mismatch is less than 100 nm for stitching of structures. Additional studies were performed where HeLa-cells were incubated for 24 hours on both scaffolds and cell affinity is studied. We observe in both cases that HeLa-cells attach to wall and corner segments of the periodic designs and furthermore HeLa-cells are seen stretching the full length of the individual wall segments. In summary, we show that parallelization of the fabrication process has the potential to make TPP a fast method for large volume periodic 3D structure.
关键词： Two-photon polymerization,cell interaction studies,fabrication speed,diffractive optical element,3D structures
更新于2025-09-12 10:27:22
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Femtosecond laser fabrication of 3D templates for mass production of artificial compound eyes
摘要： Compound eyes are unique optical imaging systems that consist of numerous separate light-sensitive units (ommatidia). Attempts have been made to produce artificial compound eyes via advanced 3D nanotechnologies. Among them, femtosecond laser direct writing (FsLDW) technology has emerged as an effective strategy due to its distinct advantages in 3D designable and high precision fabrication capability. However, the point-by-point scanning process results in a very low fabrication efficiency, limiting the practical applications of the FsLDW technology. To solve this problem, we propose a high-efficiency method for the mass production of 3D artificial compound eyes using a photopolymer template fabricated by FsLDW. The resultant 3D SU-8 compound eye templates could be used to replicate polydimethylsiloxane (PDMS) compound eyes many times (over 50 times) with a highly improved efficiency (nearly 20 times higher than the efficiency of direct fabrication using the point-by-point FsLDW). The PDMS replicas showed good focusing and imaging performances. We anticipate that this method may serve as an enabler for the mass production of 3D artificial compound eyes and promote their practical applications in the near future.
关键词： Two-photon polymerization,Compound eyes,PDMS casting,Femtosecond laser
更新于2025-09-12 10:27:22
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Two-Photon Polymerization as a Tool for Studying 3D Printed Topography-Induced Stem Cell Fate
摘要： Geometric topographies are known to influence cellular differentiation toward specific phenotypes, but to date the range of features and type of substrates that can be easily fabricated to study these interactions is somewhat limited. In this study, an emerging technology, two-photon polymerization, is used to print topological patterns with varying feature-size and thereby study their effect on cellular differentiation. This technique offers rapid manufacturing of topographical surfaces with good feature resolution for shapes smaller than 3 μm. Human-induced pluripotent stem cells, when attached to these substrates or a non-patterned control for 1 week, express an array of genetic markers that suggest their differentiation toward a heterogeneous population of multipotent progenitors from all three germ layers. Compared to the topographically smooth control, small features (1.6 μm) encourage differentiation toward ectoderm while large features (8 μm) inhibit self-renewal. This study demonstrates the potential of using two-photon polymerization to study and control stem cell fate as a function of substrate interactions. The ability to tailor and strategically design biomaterials in this way can enable more precise and efficient generation or maintenance of desired phenotypes in vitro and in vivo.
关键词： induced pluripotent stem cells,differentiation,substrate topography,3D printing,two-photon polymerization
更新于2025-09-10 09:29:36
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Micro-Dumbbells—A Versatile Tool for Optical Tweezers
摘要： Manipulation of micro- and nano-sized objects with optical tweezers is a well-established, albeit still evolving technique. While many objects can be trapped directly with focused laser beam(s), for some applications indirect manipulation with tweezers-operated tools is preferred. We introduce a simple, versatile micro-tool operated with holographic optical tweezers. The 40 μm long dumbbell-shaped tool, fabricated with two-photon laser 3D photolithography has two beads for efficient optical trapping and a probing spike on one end. We demonstrate fluids viscosity measurements and vibration detection as examples of possible applications.
关键词： direct laser writing,3D lithography,optical tweezers,viscosity,two-photon polymerization,micro-tool,optical trapping
更新于2025-09-10 09:29:36
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Rotational Efficiency of Photo-Driven Archimedes Screws for Micropumps
摘要： In this study, we characterized the rotational efficiency of the photo-driven Archimedes screw. The micron-sized Archimedes screws were fabricated using the two-photon polymerization technique. Free-floating screws trapped by optical tweezers align in the laser irradiation direction and rotate spontaneously. The influences of the screw pitch and the number of screw blades have been investigated in our previous studies. In this paper, the blade thickness and the central rod of the screw were further investigated. The experimental results indicate that the blade thickness contributes to rotational stability, but not to rotational speed, and that the central rod stabilizes the rotating screw but is not conducive to rotational speed. Finally, the effect of the numerical aperture (NA) of the optical tweezers was investigated through a demonstration. The NA is inversely proportional to the rotational speed.
关键词： two-photon polymerization,micropump,optical torque,Archimedes screw,optical tweezers
更新于2025-09-04 15:30:14
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Desenvolvimento de um obturador de feixe óptico utilizando um disco rígido de computador
摘要： This work demonstrates the development of an optical shutter from a computer hard disk. The electrical current control of the device is made by pulse width modulation, a technique that allows varying current/voltage levels by adjusting the pulse width of a digital signal. This control is made in order to minimize the power dissipated into the device, thus raising its lifetime. The main unit of the control circuit is Arduino Uno, a low cost and ease of programming microcontroller board, extensively used as a platform for electronic prototyping. As an example, we present the use of an optical shutter developed in a microfabrication setup via two-photon polymerization, in which it plays an important role.
关键词： Optical shutter,Arduino Uno,pulse width modulation,two-photon polymerization
更新于2025-09-04 15:30:14
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Three-Dimensional Photonic Structures Fabricated by Two-Photon Polymerization for Microfluidics and Microneedles
摘要： Polymer micro- and nanostructures with various geometries, such as lines, gratings, woodpiles or dots, can be written onto a transparent substrate by the technique of two-photon polymerization, i.e. focusing a femtosecond laser into a liquid acrylate based resin containing a photo-initiator. The microstructures can be also employed to mimic features found in nature for controlled wetting or liquid transport. Similar structures can be implemented into channels of microfluidic devices to control the transport of fluids herein. In preliminary experiments, we were able to produce microneedles ornamented with microstructures which would facilitate the transport of an aqueous liquid to the needle tip.
关键词： two-photon polymerization,directed fluid transport,microneedles,microfluidics,photonic structures
更新于2025-09-04 15:30:14