Journal articles: 'Two-photon polymerization lithography'

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Purtov, Julia, Peter Rogin, Andreas Verch, Villads Egede Johansen, and René Hensel. "Nanopillar Diffraction Gratings by Two-Photon Lithography." Nanomaterials 9, no. 10 (October 19, 2019): 1495. http://dx.doi.org/10.3390/nano9101495.

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Two-dimensional photonic structures such as nanostructured pillar gratings are useful for various applications including wave coupling, diffractive optics, and security features. Two-photon lithography facilitates the generation of such nanostructured surfaces with high precision and reproducibility. In this work, we report on nanopillar diffraction gratings fabricated by two-photon lithography with various laser powers close to the polymerization threshold of the photoresist. As a result, defect-free arrays of pillars with diameters down to 184 nm were fabricated. The structure sizes were analyzed by scanning electron microscopy and compared to theoretical predictions obtained from Monte Carlo simulations. The optical reflectivities of the nanopillar gratings were analyzed by optical microscopy and verified by rigorous coupled-wave simulations.

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Yang, Da, Shalin J. Jhaveri, and Christopher K. Ober. "Three-Dimensional Microfabrication by Two-Photon Lithography." MRS Bulletin 30, no. 12 (December 2005): 976–82. http://dx.doi.org/10.1557/mrs2005.251.

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AbstractThe controlled formation of submicrometer-scale structures in three dimensions is of increasing interest in many applications. Not intended to produce the smallest structures, but instead aimed at complex topographies, two-photon lithography is an intrinsic 3D lithography technique that enables the fabrication of structures difficult to access by conventional single-photon processes with far greater spatial resolution than other 3D microfabrication techniques. By tightly focusing a femtosecond laser beam into a resin, subsequent photo-induced reactions such as polymerization occur only in the close vicinity of the focal point, allowing the fabrication of a 3D structure by directly writing 3D patterns. The current research effort in two-photon lithography is largely devoted to the design and synthesis of high-efficiency photoinitiators and sensitizers, as well as the development of new materials and systems. This article provides an overview of the progress in two-photon processes for the formation of complex images and the development of patterned structures.

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Pisanello, Marco, Di Zheng, Antonio Balena, Filippo Pisano, Massimo De Vittorio, and Ferruccio Pisanello. "An open source three-mirror laser scanning holographic two-photon lithography system." PLOS ONE 17, no. 4 (April 15, 2022): e0265678. http://dx.doi.org/10.1371/journal.pone.0265678.

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Two-photon polymerization is a widely adopted technique for direct fabrication of 3D and 2D structures with sub-diffraction-limit features. Here we present an open-hardware, open-software custom design for a holographic multibeam two-photon polymerization system based on a phase-only spatial light modulator and a three-mirror scanhead. The use of three reflective surfaces, two of which scanning the phase-modulated image along the same axis, allows to overcome the loss of virtual conjugation within the large galvanometric mirrors pair needed to accommodate the holographic projection. This extends the writing field of view among which the hologram can be employed for multi-beam two-photon polymerization by a factor of ~2 on one axis (i.e. from ~200μm to ~400μm), with a voxel size of ~250nm × ~1050nm (lateral × axial size), and writing speed of three simultaneous beams of 2000 voxels/s, making our system a powerful and reliable tool for advanced micro and nano-fabrications on large area.

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Leong, Stephen, Aykut Aksit, Sharon J. Feng, Jeffrey W. Kysar, and Anil K. Lalwani. "Inner Ear Diagnostics and Drug Delivery via Microneedles." Journal of Clinical Medicine 11, no. 18 (September 17, 2022): 5474. http://dx.doi.org/10.3390/jcm11185474.

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Objectives: Precision medicine for inner ear disorders has seen significant advances in recent years. However, unreliable access to the inner ear has impeded diagnostics and therapeutic delivery. The purpose of this review is to describe the development, production, and utility of novel microneedles for intracochlear access. Methods: We summarize the current work on microneedles developed using two-photon polymerization (2PP) lithography for perforation of the round window membrane (RWM). We contextualize our findings with the existing literature in intracochlear diagnostics and delivery. Results: Two-photon polymerization lithography produces microneedles capable of perforating human and guinea pig RWMs without structural or functional damage. Solid microneedles may be used to perforate guinea pig RWMs in vivo with full reconstitution of the membrane in 48–72 h, and hollow microneedles may be used to aspirate perilymph or inject therapeutics into the inner ear. Microneedles produced with two-photon templated electrodeposition (2PTE) have greater strength and biocompatibility and may be used to perforate human RWMs. Conclusions: Microneedles produced with 2PP lithography and 2PTE can safely and reliably perforate the RWM for intracochlear access. This technology is groundbreaking and enabling in the field of inner ear precision medicine.

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Lee, Eung-Sug, Jun-Ho Jeong, Ki-Don Kim, Young-Suk Sim, Dae-Geun Choi, Junhyuk Choi, Sang-Hu Park, et al. "Fabrication of Nano- and Micro-Scale UV Imprint Stamp Using Diamond-Like Carbon Coating Technology." Journal of Nanoscience and Nanotechnology 6, no. 11 (November 1, 2006): 3619–23. http://dx.doi.org/10.1166/jnn.2006.17994.

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Two-dimensional (2-D) and three-dimensional (3-D) diamond-like carbon (DLC) stamps for ultraviolet nanoimprint lithography were fabricated with two methods: namely, a DLC coating process, followed by focused ion beam lithography; and two-photon polymerization patterning, followed by nanoscale-thick DLC coating. We used focused ion beam lithography to fabricate 70 nm deep lines with a width of 100 nm, as well as 70 nm deep lines with a width of 150 nm, on 100 nm thick DLC layers coated on quartz substrates. We also used two-photon polymerization patterning and a DLC coating process to successfully fabricate 200 nm wide lines, as well as 3-D rings with a diameter of 1.35 μm and a height of 1.97 μm, and a 3-D cone with a bottom diameter of 2.88 μm and a height of 1.97 μm. The wafers were successfully printed on an UV-NIL using the DLC stamps without an anti-adhesive layer. The correlation between the dimensions of the stamp's features and the corresponding imprinted features was excellent.

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Li, Zhiquan, Arnulf Rosspeintner, Peng Hu, Guigang Zhu, Yuansheng Hu, Xiang Xiong, Ruwen Peng, Mu Wang, Xiaoya Liu, and Ren Liu. "Silyl-based initiators for two-photon polymerization: from facile synthesis to quantitative structure–activity relationship analysis." Polymer Chemistry 8, no. 43 (2017): 6644–53. http://dx.doi.org/10.1039/c7py01360d.

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Abel, T., R. Dörr, W. Krüger, R. Horstmann, G. Schaumann, M. Roth, and H. F. Schlaak. "Combining two-photon-polymerization with UV-lithography for laser particle acceleration targets." Journal of Physics: Conference Series 1079 (August 2018): 012012. http://dx.doi.org/10.1088/1742-6596/1079/1/012012.

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Dias, Guilherme Osvaldo, Olivier Lecarme, Julien Cordeiro, Emmanuel Picard, and David Peyrade. "Microscale white light emitters fabricated by two-photon polymerization lithography on functional resist." Microelectronic Engineering 257 (March 2022): 111751. http://dx.doi.org/10.1016/j.mee.2022.111751.

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Yuan, Chenyu, Jukun Liu, Tianqing Jia, Kan Zhou, Hongxin Zhang, Jia Pan, Donghai Feng, and Zhenrong Sun. "Super resolution direct laser writing in ITX resist inspired by STED microscopy." Journal of Nonlinear Optical Physics & Materials 23, no. 02 (June 2014): 1450015. http://dx.doi.org/10.1142/s0218863514500155.

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Direct laser writing (DLW) has become a routine tool for fabricating microstructures through two photon polymerization. Due to the diffraction limit, the resolution is usually larger than a quarter of a wavelength. In this article, by using stimulated emission depletion (STED) inspired lithography, we fabricate nanodot of 81 nm in diameter and nanoline of 93 nm in width in resist with initiator of isopropyl thioxanthone (ITX). An 800 nm, 75-MHz fs laser works as the polymerization light and a 532 nm donut mode continuous wave (CW) laser as the depletion light. This technology is potentially useful for fabrication of super resolution nanostructures.

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Ushiba, Shota, Satoru Shoji, Kyoko Masui, Preeya Kuray, Junichiro Kono, and Satoshi Kawata. "3D microfabrication of single-wall carbon nanotube/polymer composites by two-photon polymerization lithography." Carbon 59 (August 2013): 283–88. http://dx.doi.org/10.1016/j.carbon.2013.03.020.

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Egorov, Anton E., Alexey A. Kostyukov, Denis A. Shcherbakov, Danila A. Kolymagin, Dmytro A. Chubich, Rilond P. Matital, Maxim V. Arsenyev, et al. "Benzylidene Cyclopentanone Derivative Photoinitiator for Two-Photon Photopolymerization-Photochemistry and 3D Structures Fabrication for X-ray Application." Polymers 15, no. 1 (December 24, 2022): 71. http://dx.doi.org/10.3390/polym15010071.

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Micron- and submicron-scale 3D structure realization nowadays is possible due to the two-photon photopolymerization (TPP) direct laser writing photolithography (DLW photolithography) method. However, the achievement of lithographic features with dimensions less than 100 nm is in demand for the fabrication of micro-optical elements with high curvature values, including X-ray microlenses. Spectroscopic and photochemical study of a photoinitiator (PI) based on a methyl methacrylate derivative of 2,5-bis(4-(dimethylamino)benzylidene) cyclopentanone was performed. Enhanced intersystem crossing in the methyl methacrylate derivative results in increased radical generation for the subsequent initiation of polymerization. A comprehensive study of the new photocompositions was performed, with particular emphasis on photochemical constants, the degree of photopolymerization, and topology. The optimal parameters for the fabrication of mechanically stable structures were determined in this research. The threshold dose parameters for lithography (radiation power of 5 mW at a speed of 180 µm/s) when trying to reach saturation values with a conversion degree of (35 ± 1) % were defined, as well as parameters for sub-100 nm feature fabrication. Moreover, the 45 nm feature size for elements was reached. Fabrication of X-ray lens microstructures was also demonstrated.

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Xiao-Xia, Shen, Yu Xiao-Qiang, Yang Xiu-Lun, Cai Lv-Zhong, Wang Yu-Rong, Dong Guo-Yan, Meng Xiang-Feng, and Xu Xian-Feng. "Fabrication of Two-Dimensional Photonic Crystals with Controlled Defects by Combination of Holographic Lithography and Two-Photon Polymerization." Chinese Physics Letters 24, no. 11 (October 17, 2007): 3160–63. http://dx.doi.org/10.1088/0256-307x/24/11/039.

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13

Accoto, Celso, Antonio Qualtieri, Ferruccio Pisanello, Carlo Ricciardi, Candido Fabrizio Pirri, Massimo De Vittorio, and Francesco Rizzi. "Two-Photon Polymerization Lithography and Laser Doppler Vibrometry of a SU-8-Based Suspended Microchannel Resonator." Journal of Microelectromechanical Systems 24, no. 4 (August 2015): 1038–42. http://dx.doi.org/10.1109/jmems.2014.2376986.

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Philipp, N., S. Angriman, S. Burne, P. Caral, I. Gómez Florenciano, N. Rapagnani, M. Gabriel, and L. C. Estrada. "Physico-chemical elucidation of the mechanism involved in optical lithography: Micro-fabrication of 2D and 3D platforms." Journal of Applied Physics 132, no. 18 (November 14, 2022): 183104. http://dx.doi.org/10.1063/5.0123862.

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Direct laser lithography has attracted much attention as a convenient micro-fabrication method to develop rapid, free-form, and low-cost microstructures. In this work, different microdevices were fabricated using a home-made two-photon excitation microscope and a commercial negative UV photoresin. The mechanism involved during the fabrication of the devices as well as the effects of the irradiation intensity and removal time on micro-patterns was investigated by optical microscopy. For the characterization of the microstructures, scanning electron microscopy, atomic force microscopy, Nuclear Magnetic Resonance (1H-NMR), and Fourier transform infrared spectroscopy were used. High-resolution optical characterization shows an enormous uniformity and high reproducibility of fabricated platforms in two and three dimensions. These results prompted us to propose a different mechanism not compatible with a polymerization reaction as the triggering mechanism for the interaction between light and the photoresin. We demonstrate the coexistence of an allylic photo-induced reaction with a photo-induced polymerization effect during the fabrication process. We studied the influence of these mechanisms by fabricating micro-patterns in two conditions, with and without the presence of a polymerization initiator [azobisisobutyronitrile (AIBN)], which boots the polymerization reaction. Even though the two mechanisms are present during the fabrication process, the polymerization is dominant in the presence of a photo-initiator as AIBN. Finally, we discuss the applications of our microdevices as suitable platforms for industry and biomedical applications.

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Seidel, Andreas, Jacek Gosciniak, Maria U. Gonzalez, Jan Renger, Carsten Reinhardt, Roman Kiyan, Romain Quidant, Sergey I. Bozhevolnyi, and Boris N. Chichkov. "Fiber-Coupled Surface Plasmon Polariton Excitation in Imprinted Dielectric-Loaded Waveguides." International Journal of Optics 2010 (2010): 1–6. http://dx.doi.org/10.1155/2010/897829.

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We present fiber-coupled dielectric-loaded plasmonic waveguides for 1.55 μm telecom wavelength fabricated by two-photon polymerization and nanoimprint lithography. The waveguide structures include 100-μm-long plasmonic waveguides connected on both ends to tapered dielectric waveguides used for end-fire coupling with optical fibers. The excitation of plasmonic waveguides is verified via polarization-resolved measurements of the overall transmission, demonstrating thereby that this technology is suitable in principle for the integration of plasmonic components into fiberoptics. Loss mechanisms are investigated and improvements suggested to reduce transmission losses and consequently increase the viability of practical application.

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Mikhaylov, Andrey, Stefan Reich, Margarita Zakharova, Vitor Vlnieska, Roman Laptev, Anton Plech, and Danays Kunka. "Shack–Hartmann wavefront sensors based on 2D refractive lens arrays and super-resolution multi-contrast X-ray imaging." Journal of Synchrotron Radiation 27, no. 3 (April 22, 2020): 788–95. http://dx.doi.org/10.1107/s1600577520002830.

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Different approaches of 2D lens arrays as Shack–Hartmann sensors for hard X-rays are compared. For the first time, a combination of Shack–Hartmann sensors for hard X-rays (SHSX) with a super-resolution imaging approach to perform multi-contrast imaging is demonstrated. A diamond lens is employed as a well known test object. The interleaving approach has great potential to overcome the 2D lens array limitation given by the two-photon polymerization lithography. Finally, the radiation damage induced by continuous exposure of an SHSX prototype with a white beam was studied showing a good performance of several hours. The shape modification and influence in the final image quality are presented.

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Fang, Wei, Jian Lei, Pengda Zhang, Fei Qin, Meiling Jiang, Xufeng Zhu, Dejiao Hu, Yaoyu Cao, and Xiangping Li. "Multilevel phase supercritical lens fabricated by synergistic optical lithography." Nanophotonics 9, no. 6 (April 18, 2020): 1469–77. http://dx.doi.org/10.1515/nanoph-2020-0064.

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AbstractThe advent of planar metalenses, including the super-oscillatory lens (SOL) and the supercritical lens (SCL) with distinctive interference properties, has profoundly impacted on the long-lasting perception of the far-field optical diffraction limit. In spite of its conspicuous success in achieving marvelously small focal spots, the planar metalens still faces tough design and fabrication challenges to realize high focusing efficiency. In this work, we demonstrated a dual-mode laser fabrication technique based on two-photon polymerization for realizing the multilevel phase SCL with focusing efficiency spiking. Synergistically controlling two types of movement trajectory, which is implemented with the piezo stage and the scanning galvo mirror, enables the fabrication of complicated structures with sub-diffraction-limit feature size. By utilizing such advantage, SCLs with discretized multilevel phase configurations are explicitly patterned. The experimental characterization results have shown that a four-level phase SCL can focus light into a sub-diffraction-limit spot with the lateral size of 0.41 λ/NA (NA is the numerical aperture), while achieve the focal spot intensity and the energy concentration ratio in the focal region 7.2 times and 3 times that of the traditional binary amplitude-type SCL with the same optimization conditions, respectively. Our results may release the application obstacles for the sub-diffraction-limit planar metalens and enable major advances in the fields from label-free optical super-resolution imaging to high precision laser fabrication.

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Xiong, Junfeng, Xiaoxia Song, Yuhang Cai, Jiahe Liu, Yangyuan Li, Yaqiang Ji, Liang Guo, and U. Kei Cheang. "Stop-Flow Lithography for the Continuous Production of Degradable Hydrogel Achiral Crescent Microswimmers." Micromachines 13, no. 5 (May 20, 2022): 798. http://dx.doi.org/10.3390/mi13050798.

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The small size of robotic microswimmers makes them suitable for performing biomedical tasks in tiny, enclosed spaces. Considering the effects of potentially long-term retention of microswimmers in biological tissues and the environment, the degradability of microswimmers has become one of the pressing issues in this field. While degradable hydrogel was successfully used to prepare microswimmers in previous reports, most hydrogel microswimmers could only be fabricated using two-photon polymerization (TPP) due to their 3D structures, resulting in costly robotic microswimmers solution. This limits the potential of hydrogel microswimmers to be used in applications where a large number of microswimmers are needed. Here, we proposed a new type of preparation method for degradable hydrogel achiral crescent microswimmers using a custom-built stop-flow lithography (SFL) setup. The degradability of the hydrogel crescent microswimmers was quantitatively analyzed, and the degradation rate in sodium hydroxide solution (NaOH) of different concentrations was investigated. Cytotoxicity assays showed the hydrogel crescent microswimmers had good biocompatibility. The hydrogel crescent microswimmers were magnetically actuated using a 3D Helmholtz coil system and were able to obtain a swimming efficiency on par with previously reported microswimmers. The results herein demonstrated the potential for the degradable hydrogel achiral microswimmers to become a candidate for microscale applications.

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Kim, Minsu, Eun Song Oh, and Moon Kyu Kwak. "Shrinkage-Considered Mold Design for Improvement of Micro/Nano-Structured Optical Element Performance." Micromachines 11, no. 10 (October 17, 2020): 941. http://dx.doi.org/10.3390/mi11100941.

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Polymer shrinkage in nano-imprint lithography (NIL) is one of the critical issues that must be considered in order to produce a quality product. Especially, this condition should be considered during the manufacture of optical elements, because micro/nano-structured optical elements should be controlled to fit the desired shape in order to achieve the intended optical performance. In this paper, during NIL, we characterized the shrinkage of polymeric resin on micro lens array (MLA), which is one of the representative micro/nano-structured optical elements. The curvature shape and optical performance of MLA were measured to check the shrinkage tendency during the process. The master mold of MLA was generated by the two-photon polymerization (2PP) additive manufacturing method, and the tested samples were replicated from the master mold with NIL. Several types of resin were adjusted to prepare the specimens, and the shrinkage effects in each case were compared. The shrinkage showed different trends based on the NIL materials and MLA shapes. These characterizations can be applied to compensate for the MLA design, and the desired performance of MLA products can be achieved with a corrected master mold.

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Sun, Ho Cheung Michael, Pan Liao, Tanyong Wei, Li Zhang, and Dong Sun. "Magnetically Powered Biodegradable Microswimmers." Micromachines 11, no. 4 (April 13, 2020): 404. http://dx.doi.org/10.3390/mi11040404.

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The propulsive efficiency and biodegradability of wireless microrobots play a significant role in facilitating promising biomedical applications. Mimicking biological matters is a promising way to improve the performance of microrobots. Among diverse locomotion strategies, undulatory propulsion shows remarkable efficiency and agility. This work proposes a novel magnetically powered and hydrogel-based biodegradable microswimmer. The microswimmer is fabricated integrally by 3D laser lithography based on two-photon polymerization from a biodegradable material and has a total length of 200 μm and a diameter of 8 μm. The designed microswimmer incorporates a novel design utilizing four rigid segments, each of which is connected to the succeeding segment by spring to achieve undulation, improving structural integrity as well as simplifying the fabrication process. Under an external oscillating magnetic field, the microswimmer with multiple rigid segments connected by flexible spring can achieve undulatory locomotion and move forward along with the directions guided by the external magnetic field in the low Reynolds number (Re) regime. In addition, experiments demonstrated that the microswimmer can be degraded successfully, which allows it to be safely applied in real-time in vivo environments. This design has great potential in future in vivo applications such as precision medicine, drug delivery, and diagnosis.

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Herman, Matthew J., Dominic Peterson, Kevin Henderson, Tana Cardenas, Christopher E. Hamilton, John Oertel, and Brian M. Patterson. "Lithographic Printing Via Two-Photon Polymerization of Engineered Foams." Fusion Science and Technology 73, no. 2 (November 29, 2017): 166–72. http://dx.doi.org/10.1080/15361055.2017.1387454.

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Ohrt, Christoph, Yasemin Acar, Andreas Seidel, Wei Cheng, Roman Kiyan, and Boris N. Chichkov. "Fidelity of soft nano-imprint lithographic replication of polymer masters fabricated by two-photon polymerization." International Journal of Advanced Manufacturing Technology 63, no. 1-4 (January 12, 2012): 103–8. http://dx.doi.org/10.1007/s00170-011-3888-z.

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Carlotti, Marco, Omar Tricinci, Frank den Hoed, Stefano Palagi, and Virgilio Mattoli. "Direct laser writing of liquid crystal elastomers oriented by a horizontal electric field." Open Research Europe 1 (November 19, 2021): 129. http://dx.doi.org/10.12688/openreseurope.14135.2.

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Background: The ability to fabricate components capable of performing actuation in a reliable and controlled manner is one of the main research topics in the field of microelectromechanical systems (MEMS). However, the development of these technologies can be limited in many cases by 2D lithographic techniques employed in the fabrication process. Direct Laser Writing (DLW), a 3D microprinting technique based on two-photon polymerization, can offer novel solutions to prepare, both rapidly and reliably, 3D nano- and microstructures of arbitrary complexity. In addition, the use of functional materials in the printing process can result in the fabrication of smart and responsive devices. Methods: In this study, we present a novel methodology for the printing of 3D actuating microelements comprising Liquid Crystal Elastomers (LCEs) obtained by DLW. The alignment of the mesogens was performed using a static electric field (1.7 V/µm) generated by indium-tin oxide (ITO) electrodes patterned directly on the printing substrates. Results: When exposed to a temperature higher than 50°C, the printed microstructures actuated rapidly and reversibly of about 8% in the direction perpendicular to the director. Conclusions: A novel methodology was developed that allows the printing of directional actuators comprising LCEs via DLW. To impart the necessary alignment of the mesogens, a static electric field was applied before the printing process by making use of flat ITO electrodes present on the printing substrates. The resulting microelements showed a reversible change in shape when heated higher than 50 °C.

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Carlotti, Marco, Omar Tricinci, Frank den Hoed, Stefano Palagi, and Virgilio Mattoli. "Direct laser writing of liquid crystal elastomers oriented by a horizontal electric field." Open Research Europe 1 (October 25, 2021): 129. http://dx.doi.org/10.12688/openreseurope.14135.1.

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Background: The ability to fabricate components capable of performing actuation in a reliable and controlled manner is one of the main research topics in the field of microelectromechanical systems (MEMS). However, the development of these technologies can be limited in many cases by 2D lithographic techniques employed in the fabrication process. Direct Laser Writing (DLW), a 3D microprinting technique based on two-photon polymerization, can offer novel solutions to prepare, both rapidly and reliably, 3D nano- and microstructures of arbitrary complexity. In addition, the use of functional materials in the printing process can result in the fabrication of smart and responsive devices. Methods: In this study, we present a novel methodology for the printing of 3D actuating microelements comprising Liquid Crystal Elastomers (LCEs) obtained by DLW. The alignment of the mesogens was performed using a static electric field (1.7 V/µm) generated by indium-tin oxide (ITO) electrodes patterned directly on the printing substrates. Results: When exposed to a temperature higher than 50°C, the printed microstructures actuated rapidly and reversibly of about 8% in the direction perpendicular to the director. Conclusions: A novel methodology was developed that allows the printing of directional actuators comprising LCEs via DLW. To impart the necessary alignment of the mesogens, a static electric field was applied before the printing process by making use of flat ITO electrodes present on the printing substrates. The resulting microelements showed a reversible change in shape when heated higher than 50 °C.

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Lin, Yang, Can Gao, Dmitry Gritsenko, Ran Zhou, and Jie Xu. "Soft lithography based on photolithography and two-photon polymerization." Microfluidics and Nanofluidics 22, no. 9 (August 23, 2018). http://dx.doi.org/10.1007/s10404-018-2118-5.

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Pingali, Rushil, and Sourabh K. Saha. "Reaction-Diffusion Modeling of Photopolymerization During Femtosecond Projection Two-Photon Lithography." Journal of Manufacturing Science and Engineering 144, no. 2 (August 5, 2021). http://dx.doi.org/10.1115/1.4051830.

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Abstract Two-photon lithography (TPL) is a polymerization-based direct laser writing process that is capable of fabricating arbitrarily complex three-dimensional (3D) structures with submicron features. Traditional TPL techniques have limited scalability due to the slow point-by-point serial writing scheme. The femtosecond projection TPL (FP-TPL) technique increases printing rate by a thousand times by enabling layer-by-layer parallelization. However, parallelization alters the time and the length scales of the underlying polymerization process. It is therefore challenging to apply the models of serial TPL to accurately predict process outcomes during FP-TPL. To solve this problem, we have generated a finite element model of the polymerization process on the time and length scales relevant to FP-TPL. The model is based on the reaction-diffusion mechanism that underlies polymerization. We have applied this model to predict the geometry of nanowires printed under a variety of conditions and compared these predictions against empirical data. Our model accurately predicts the nanowire widths. However, accuracy of aspect ratio prediction is hindered by uncertain values of the chemical properties of the photopolymer. Nevertheless, our results demonstrate that the reaction-diffusion model can accurately capture the effect of controllable parameters on FP-TPL process outcome and can therefore be used for process control and optimization.

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Kumpfmueller, Josef, Klaus Stadlmann, Zhiquan Li, Valentin Satzinger, Juergen Stampfl, and Robert Liska. "Flexible Optical Interconnects via Thiol-ene Two-photon-induced Polymerization." MRS Proceedings 1438 (2012). http://dx.doi.org/10.1557/opl.2012.1408.

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ABSTRACTTwo-photon polymerization (2PP) is an emerging tool in the field of additive manufacturing technologies, which allows for the elegant 3D lithographic production by means of photosensitive resins. One key advantage of 2PP is the achievable feature resolution. A few tens of nanometers are currently the resolution limit for this novel technique. Fields of applications are as diverse as photonics, microfluidics and biomedicine.A challenging photonics application for 2PP are optical interconnects, where optical elements on printed circuit boards are connected with waveguides. The possibility for real 3D structuring allows for easier positioning of the cured structures and straightforward processing outperforming techniques such as 2D lithography or reactive ion etching in this regard. If mechanical flexibility of the printed circuit board is required as a property for certain niche applications, polysiloxanes are an interesting class of matrix material. This is also due to their low optical damping behavior and high temperature stability as the material has to withstand temperatures around 250°C during the manufacturing process. In this work, we present our latest approach to create polysiloxane-based waveguides via 2PP of specially tailored thiol-ene formulations. Latest improvements on the ease of processing and the local refractive index increase are shown as well as the proof of principle for waveguiding. Optical waveguides were successfully created via 2PP with writing speeds around 10 mm/min.

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Schweiger, Severin, Tim Schulze, Simon Schlipf, Peter Reinig, and Harald Schenk. "Characterization of two-photon-polymerization lithography structures via Raman spectroscopy and nanoindentation." Journal of Optical Microsystems 2, no. 03 (August 10, 2022). http://dx.doi.org/10.1117/1.jom.2.3.033501.

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Qin, Xiao-Hua, Aleksandr Ovsianikov, Jürgen Stampfl, and Robert Liska. "Additive manufacturing of photosensitive hydrogels for tissue engineering applications." BioNanoMaterials 15, no. 3-4 (January 1, 2014). http://dx.doi.org/10.1515/bnm-2014-0008.

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AbstractHydrogels are extensively explored as scaffolding materials for 2D/3D cell culture and tissue engineering. Owing to the substantial complexity of tissues, it is increasingly important to develop 3D biomimetic hydrogels with user-defined architectures and controllable biological functions. To this end, one promising approach is to utilize photolithography-based additive manufacturing technologies (AMTs) in combination with photosensitive hydrogels. We here review recent advances in photolithography-based additive manufacturing of 3D hydrogels for tissue engineering applications. Given the importance of materials selection, we firstly give an overview of water-soluble photoinitiators for single- and two-photon polymerization, photopolymerizable hydrogel precursors and light-triggered chemistries for hydrogel formation. Through the text we discuss the design considerations of hydrogel precursors and synthetic approaches to polymerizable hydrogel precursors of synthetic and natural origins. Next, we shift to how photopolymerizable hydrogels could integrate with photolithography-based AMTs for creating well-defined hydrogel structures. We illustrate the working-principles of both single- and two-photon lithography and case studies of their applications in tissue engineering. In particular, two-photon lithography is highlighted as a powerful tool for 3D functionalization/construction of hydrogel constructs with μm-scale resolution. Within the text we also explain the chemical reactions involved in two-photon-induced biofunctionalization and polymerization. In the end, we summarize the limitations of available hydrogel systems and photolithography-based AMTs as well as a future outlook on potential optimizations.

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Singh, Gaganpreet, Deepak Mishra, Janakarajan Ramkumar, and Subramanian Anantha Ramakrishna. "Large area fabrication of single micron features using two-photon polymerization with sub-nanosecond laser." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, March 10, 2022, 095440542210777. http://dx.doi.org/10.1177/09544054221077781.

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Single micrometer-sized features were fabricated on ARN-4340 photoresist using a 3D additive technique of two-photon polymerization (TPP). An economic TPP setup capable of producing a large area was developed in the lab using a sub-nanosecond laser. The Photo-initiator (2, 4 Diethyl-9H-thioxanthen-9-one) with a large two-photon absorption cross-section was used to enhance the polymerization. It was theoretically determined that the dimensions of the polymerized features depend on the concentration of the photo-initiator. A novel image-based focusing technique was developed to achieve uniform microsized features on a large area. In the proposed TPP setup, the developed focusing technique was used to determine the area over the sample, which can be polymerized in one go. To demonstrate the capability of the developed setup, microstructures of about 1 µm width were fabricated over an area of 4 cm2. Further, the fabricated sample was used to develop a master mold of Polydimethylsiloxane, which can be used for a soft-lithography replication process. Also, the melt flow technique was explored to reduce the roughness in the fabricated structure. The multi-photon polymerization process using the sub-nanosecond laser is shown to be cost-effective and robust for large area microstructure fabrication.

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Ruggiero, Amedeo, Valeria Criscuolo, Sara Grasselli, Ugo Bruno, Chiara Ausilio, Claudia Latte Bovio, Ottavia Bettucci, and Francesca Santoro. "Two-photon polymerization lithography enabling the fabrication of PEDOT:PSS 3D structures for bioelectronic applications." Chemical Communications, 2022. http://dx.doi.org/10.1039/d2cc03152c.

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Conductive 3D platforms have gained an increasing attention in bioelectronics thanks to the improvement in the cell-chip coupling. PEDOT:PSS is nowadays widely employed in bioelectronic applications thanks to its electrical...

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Samsonas, Danielius, Edvinas Skliutas, Arūnas Čiburys, Lukas Kontenis, Darius Gailevičius, Jonas Berzinš, Donatas Narbutis, et al. "3D nanopolymerization and damage threshold dependence on laser wavelength and pulse duration." Nanophotonics, January 13, 2023. http://dx.doi.org/10.1515/nanoph-2022-0629.

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Abstract The dependence of the polymerization and optical damage thresholds in multi-photon polymerization (MPP) lithography was studied using a broadly-tunable laser system with group delay dispersion (GDD) control. The order of non-linearity and the light–matter interaction mechanisms were investigated using the resolution bridges method for non-photosensitized SZ2080TM and photosensitized SZ2080TM + IRG369 prepolymers. Energy deposition, voxel dimension growth, and the size of the dynamic fabrication window (DFW) were measured in the 700–1300 nm wavelength range at three different pulse durations measured at the sample – 100, 200 and 300 fs. Polymerization was observed at all wavelengths and pulse durations without significant differences in the achieved minimal spatial dimension ( < 300 $< 300$ nm). This was achieved despite the broad range of excitation wavelengths used which spanned two- and three-photon absorption bands, and the differences in the absorption spectra of the prepolymers. The lateral and longitudinal voxel growth dynamics revealed an abrupt change in the power dependence of polymerization and a significant variation of the DFW – from 1 at 1250 nm to 29 at 700 nm. This result can be interpreted as a consequence of a change in the instantaneous refractive index and a lowering of the polymerization but not the damage threshold. The optimization of energy delivery to the material by a wavelength-tunable laser source with pulse duration control was experimentally validated. These findings are uncovering the complexity of polymerization mechanisms and are useful in further development of MPP technology.

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Houbertz, R., J. Schulz, L. Fröhlich, G. Domann, M. Popall, J. Serbin, and B. Chichkov. "Inorganic-organic Hybrid Materials for Real 3-D Sub-νm Lithography." MRS Proceedings 780 (2003). http://dx.doi.org/10.1557/proc-780-y4.12.

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AbstractReal 3-D sub-νm lithography was performed with two-photon polymerization (2PP) using inorganic-organic hybrid polymer (ORMOCER®) resins. The hybrid polymers were synthesized by hydrolysis/polycondensation reactions (modified sol-gel synthesis) which allows one to tailor their material properties towards the respective applications, i.e., dielectrics, optics or passivation. Due to their photosensitive organic functionalities, ORMOCER®s can be patterned by conventional photo-lithography as well as by femtosecond laser pulses at 780 nm. This results in polymerized (solid) structures where the non-polymerized parts can be removed by conventional developers.ORMOCER® structures as small as 200 nm or even below were generated by 2PP of the resins using femtosecond laser pulses. It is demonstrated that ORMOCER®s have the potential to be used in components or devices built up by nm-scale structures such as, e.g., photonic crystals. Aspects of the materials in conjunction to the applied technology are discussed.

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Grabulosa, Adrià, Johnny Moughames, Xavier Porte, and Daniel Brunner. "Combining one and two photon polymerization for accelerated high performance (3 + 1)D photonic integration." Nanophotonics, March 29, 2022. http://dx.doi.org/10.1515/nanoph-2021-0733.

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Abstract Dense and efficient circuits with component sizes approaching the physical limit is the hallmark of high performance integration. Ultimately, these features and their pursuit enabled the multi-decade lasting exponential increase of components on integrated electronic chips according to Moore’s law, which culminated with the high performance electronics we know today. However, current fabrication technology is mostly constrained to 2D lithography, and thermal energy dissipation induced by switching electronic signal lines presents a fundamental challenge for truly 3D electronic integration. Photonics reduces this problem, and 3D photonic integration is therefore a highly sought after technology that strongly gains in relevance due to the need for scalable application-specific integrated circuits for neural networks. Direct laser writing of a photoresin is a promising high-resolution and complementary metal-oxide-semiconductor (CMOS) compatible tool for 3D photonic integration. Here, we combine one and two-photon polymerization (TPP) for waveguide integration for the first time, dramatically accelerating the fabrication process and increasing optical confinement. 3D additive printing is based on femtosecond TPP, while blanket irradiation with a UV lamp induces one-photon polymerization (OPP) throughout the entire 3D chip. We locally and dynamically adjust writing conditions to implement (3 + 1)D flash-TPP: waveguide cores are printed with a small distance between neighboring writing voxels to ensure smooth interfaces, mechanical support structures are printed at maximal distance between the voxels to speed up the process. Finally, the entire chip’s passive volume not part of waveguide cores or mechanical support is polymerized in a single instance by UV blanket irradiation. This decouples fabrication time from the passive volume’s size. We succeed in printing vertical single-mode waveguides of 6 mm length that reach numerical apertures up to NA = 0.16. Noteworthy, we achieve exceptionally low −0.26 dB injection losses and very low propagation losses of −1.36 dB/mm at λ 0 = 660 nm, which is within one order of magnitude of standard integrated silicon photonics. Finally, the optical performance of our waveguides does not deteriorate for at least ∼3000 h after printing, and remains stable during ∼600 h of continuous operation with 0.25 mW injected light.

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Chan, John You En, Qifeng Ruan, Menghua Jiang, Hongtao Wang, Hao Wang, Wang Zhang, Cheng-Wei Qiu, and Joel K. W. Yang. "High-resolution light field prints by nanoscale 3D printing." Nature Communications 12, no. 1 (June 17, 2021). http://dx.doi.org/10.1038/s41467-021-23964-6.

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AbstractA light field print (LFP) displays three-dimensional (3D) information to the naked-eye observer under ambient white light illumination. Changing perspectives of a 3D image are seen by the observer from varying angles. However, LFPs appear pixelated due to limited resolution and misalignment between their lenses and colour pixels. A promising solution to create high-resolution LFPs is through the use of advanced nanofabrication techniques. Here, we use two-photon polymerization lithography as a one-step nanoscale 3D printer to directly fabricate LFPs out of transparent resin. This approach produces simultaneously high spatial resolution (29–45 µm) and high angular resolution (~1.6°) images with smooth motion parallax across 15 × 15 views. Notably, the smallest colour pixel consists of only a single nanopillar (~300 nm diameter). Our LFP signifies a step towards hyper-realistic 3D images that can be applied in print media and security tags for high-value goods.

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Zhang, Wang, Hao Wang, Hongtao Wang, John You En Chan, Hailong Liu, Biao Zhang, Yuan-Fang Zhang, et al. "Structural multi-colour invisible inks with submicron 4D printing of shape memory polymers." Nature Communications 12, no. 1 (January 4, 2021). http://dx.doi.org/10.1038/s41467-020-20300-2.

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AbstractFour-dimensional (4D) printing of shape memory polymer (SMP) imparts time responsive properties to 3D structures. Here, we explore 4D printing of a SMP in the submicron length scale, extending its applications to nanophononics. We report a new SMP photoresist based on Vero Clear achieving print features at a resolution of ~300 nm half pitch using two-photon polymerization lithography (TPL). Prints consisting of grids with size-tunable multi-colours enabled the study of shape memory effects to achieve large visual shifts through nanoscale structure deformation. As the nanostructures are flattened, the colours and printed information become invisible. Remarkably, the shape memory effect recovers the original surface morphology of the nanostructures along with its structural colour within seconds of heating above its glass transition temperature. The high-resolution printing and excellent reversibility in both microtopography and optical properties promises a platform for temperature-sensitive labels, information hiding for anti-counterfeiting, and tunable photonic devices.

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Journal articles on the topic 'Two-photon polymerization lithography'

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