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Digital mask projection lithography (DMPL) technology is gaining significant attention due to its characteristics of free-mask, flexibility, and low cost. However, when dealing with target layouts featuring sizes smaller than the wavelength scale, accurately producing resist patterns that closely match the target layout using conventional methods to design the modulation coefficients of digital masks produced by spatial light modulators (SLM) becomes challenging. Here, we present digital inversion lithography technology (DILT), which offers what we believe to be a novel approach to reverse engineer the modulation coefficients of digital masks. In the case of binary amplitude modulation, DILT achieves a remarkable reduction in pattern errors (PE), reaching the original 0.26. At the same time, in the case of the gray amplitude modulation, the PE can be reduced to the original 0.05, which greatly improves the high-fidelity transfer of the target layout. This significant improvement enhances the accuracy of target design transfer. By leveraging the capabilities of DILT, DMPL can now attain higher precision and reliability, paving the way for more advanced applications in the field of micro-nano device manufacturing.
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When the critical dimension (CD) of resist patterns nears the resolution limit of the digital micromirror device (DMD) maskless projection lithography (DMD-MPL), significant distortion can emerge in the silicon wafer due to the optical proximity effect (OPE). The significant distortion (breakpoints, line-end scaling, corner rounding, etc.) between resist patterns and target patterns results in reduced lithographic quality. To address this issue, we have proposed a pixel-based optical proximity correction (PB-OPC) method used for the hot-spot patterns with subwavelength sizes specifically designed for DMD-MPL. Employing an end-to-end learning neural network, the PB-OPC algorithm is both straightforward and efficient. A well-trained U-net framework facilitates the mapping from unoptimized masks to optimized masks. Experimental exposure trials have demonstrated that this method not only corrects OPC in general patterns but also effectively rectifies hot-spot patterns. The pattern error (PE) value can be reduced by about 30% in the design layouts. We believe this approach holds the potential to enhance the resolution and fidelity of resist patterns in DMD maskless lithography.
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The Dammann grating (DG), which redistributes a collimated laser beam into a spot array with a uniform intensity, is a widely adopted approach for profile measurement. Conventional DGs for dense spot projection are binary phase gratings with precisely designed groove structures, which suffer from low efficiency, poor uniformity, and a hard-to-fabricate fine feature size when utilized for a large field of view (FOV). Here, we propose a new, to the best of our knowledge, hybrid DG architecture consisting of two different grating periods which effectively generates an engineering M2 × N2 spot array with a non-complex structural design. As a proof-of-concept, a dual-period hybrid DG with a two-scale grating period ratio of 11.88â µm/95.04â µm (â¼1/8) is designed and fabricated as a means to generate a dense 72 × 72 diffraction spot array with a FOV of 17° × 17°. In addition, the DG exhibits superior performance, with a high efficiency (>60%) and a low non-uniformity (<18%) at a wavelength of 532â nm. This kind of hybrid DG constructed from photoresist patterns with a minimum feature size of â¼1.2 µm can be perfectly fabricated by maskless projection lithography for large-scale and low-cost production. The proposed dual-period hybrid DG can pave the way for depth-perception-related applications such as face unlocking and motion sensing.
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Neural network-based inverse lithography technology (NNILT) has been used to improve the computational efficiency of large-scale mask optimization for advanced photolithography. NNILT is now mostly based on labels, and its performance is affected by the quality of labels. It is difficult for NNILT to achieve high performance and extrapolation ability for mask optimization without using labels. Here, we propose a label-free NNILT (LF-NNILT), which is implemented completely without labels and greatly improves the printability of the target layouts and the manufacturability of the synthesized masks compared to the traditional ILT. More importantly, the optimization speed of LF-NNILT is two orders of magnitude faster than the traditional ILT. Furthermore, LF-NNILT is simpler to implement and can achieve better solvers to support the development of advanced lithography.
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Redes Neurais de Computação , Impressão , TecnologiaRESUMO
Maskless lithography technologies have been developed and played an important role in the fabrication of functional micronano devices for microelectronics, biochips and photonics. Optical projection lithography based on digital micromirror device (DMD) is an efficient maskless lithography technology that can rapidly fabricate complex structures. The precise modulation of gap width by DMD maskless optical projection lithography (MOPL) using femtosecond laser becomes important for achieving micronano structures. Herein, we have investigated the relationship between the structure morphology and the light intensity distribution at the image plane by multi-slit diffraction model and Abbe imaging principle, and optimized the gap width more accurately by modulating exposure energy. The aperture diameter of the objective lens has a substantial effect on the pattern consistency. The continuously adjustable structural gap widths of 2144â nm, 2158â nm and 1703 nm corresponding to 6, 12, 24 pixels are obtained by varying the exposure energy in the home-built MOPL system. However, the ideal gap structure cannot be obtained only by adjusting the exposure energy when the gap width is small, such as 1 or 2 pixels. Furthermore, we have proposed an alternative way to achieve fine gap structures through the structural decomposition design and precise control of exposure energy in different regions without changing the MOPL optical system. This study would provide a promising protocol for fabricating gap microstructures with controllable configuration using MOPL technique.
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It's critically important to construct arbitrary inorganic features with high resolution. As an inorganic photoresist, hydrogen silsesquioxane (HSQ) has been patterned by irradiation sources with short wavelength, such as EUV and electron beam. However, the fabrication of three- dimensional nanoscale HSQ features utilizing infrared light sources is still challenging. Here, we demonstrate femtosecond laser direct writing (FsLDW) of HSQ through multi-photon absorption process. 26 nm feature size is achieved by using 780 nm fs laser, indicating super-diffraction limit photolithography of λ/30 for HSQ. HSQ microstructures by FsLDW possess nanoscale resolution, smooth surface, and thermal stability up to 600 °C. Furthermore, we perform FsLDW of HSQ to construct structural colour and Fresnel lens with desirable optical properties, thermal and chemical resistance. This study demonstrates that inorganic features can be flexibly achieved by FsLDW of HSQ, which would be prospective for fabricating micro-nano devices requiring nanoscale resolution, thermal and chemical resistance.
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In many integrated optics systems, grating couplers are a key component of interfacing the external light source with in-plane photonic devices. Grating couplers with dual-band capability are often desired for expanding the operation spectrum of photonic systems. Here, we propose and theoretically investigate, for the first time, a 4.95 µm-8.5 µm dual-band grating coupler on a Ge-on-SOI platform. In addition to conventional structures, Bragg gratings are introduced to two wavelength division directions for crosstalk suppression. With this design, the simulated coupling efficiencies have respectively reached 59.93% and 46.38% for the 4.95 µm and 8.5 µm bands. This mid-infrared dual-band grating coupler may be useful for defense and environmental monitoring applications.
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In digital micromirror device (DMD)-based projection photolithography, the throughput largely depends on the effectiveness of the laser energy utilization, which is directly correlated to the diffraction efficiency of DMD. Here, to optimize the DMD diffraction efficiency and thus the laser energy utilization, we calculate the diffraction efficiencies Ediffraction of DMD with various pitch sizes at wavelengths ranging from 200 nm to 800 nm, using the two-dimensional blazed grating diffraction theory. Specifically, the light incident angle is optimized for 343 nm laser and 7.56 µm pitch-size DMD, and the maximum single-order diffraction efficiency Ediffraction is increased from 40% to 96%. Experimentally, we use the effective energy utilization ηeff = Ediffraction,(m,n)/Σ[Ediffraction,(m,n)] at the entrance pupil plane of the objective to verify the effectiveness of the optimized illumination angle in a lithography illumination system with parallel beams of two wavelengths (343 nm and 515 nm). The ηeff of a "blaze" order at a 34° angle of incidence can be optimized up to 88%. The experimental results are consistent with the tendency of the calculated results, indicating that this optimization model can be used to improve the energy utilization of projection lithography with the arbitrarily designable wavelengths and the DMD's pitch size.
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In this paper, silver micro/nanostructures composed of sintered nanoparticles were printed by capturing silver nanoparticles in water with 800 nm femtosecond laser trapping. Relationships of laser power, scanning speed, nanoparticle concentration, and the width and morphology of fabricated silver wire were systematically investigated. It is found that low scanning speed and high nanoparticle concentration favor the printing of silver wire with good morphology. A silver wire with width of 305 nm was printed. Electrical resistivities of printed wires are about 24 times that of bulk silver. Silver grid structures and dot arrays were printed by using this technology. Several three-dimensional silver cuboid structures were also printed. This work provides a protocol for printing of three-dimensional metallic micro/nanostructures using laser trapping. These printed structures have great application prospects in metamaterials, flexible electronics, and SERS.
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The emerging demand for device miniaturization and integration prompts the patterning technique of micronano-cross-scale structures as an urgent desire. Lithography, as a sufficient patterning technique, has been playing an important role in achieving functional micronanoscale structures for decades. As a promising alternative, we have proposed and demonstrated the maskless optical projection nanolithography (MLOP-NL) technique for efficient cross-scale patterning. A minimum feature size of 32 nm, which is λ/12 super resolution breaking the optical diffraction limit, has been achieved by a single exposure. Furthermore, multiscale two-dimensional micronano-hybrid structures with the size over hundreds of micrometers and the precision at tens of nanometers have been fabricated by simply controlling the exposure conditions. The proposed MLOP-NL technique provides a powerful tool for achieving cross-scale patterning with both large-scale and precise configuration with high efficiency, which can be potentially used in the fabrication of multiscale integrated microsystems.
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ImpressãoRESUMO
One potential way to fabricate battery-on-chip is photopatterning electrochemical energy storage materials directly on electronics through lithography, but applicable materials are primarily limited to transparent photocurable resins. The transparency of the photoresist would be sacrificed after extra addition of insoluble inorganic battery materials and conductors. Given the importance of radical polymers for their appropriate solubility, optical transparency, and radical robustness, they may have potential application in on-chip energy storage, transport, and conversion devices. Herein, an anodic photoresist is proposed by modifying the MicroChem SU8 resist with a radical polymer poly(2,2,6,6-tetramethyl-4-piperidinyl-N-oxyl methacrylate) and an ionic conductor lithium perchlorate. It can be photopatterned on silicon wafer with 10 µm scale resolution, and it exhibits charge/discharge potentials at ca. 0.68 V versus silver chloride electrode; the coulomb efficiency is regarded as nearly equaling 100%. Although the specific capacity of the photopatterned film electrode is found to be modest, 1 × 10-5 mA h·cm-2, it presents 1/8 of its theoretical electron storage ability. All-solid-state half-cells with circular features 30 µm in diameter are prepared by means of overlay exposure using the as-prepared photoresist and lithium perchlorate-modified SU8 as the anodic electrode and solid electrolyte, respectively. These results suggest a promising way of using radical polymers for the integration of electrochemical energy in microelectronics.
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We have introduced a novel water-soluble two-photon photoinitiator based on the host-guest interaction between 3,6-bis[2-(1-methyl-pyridinium)vinyl]-9-pentyl-carbazole diiodide (BMVPC) and cucurbit[7]uril (CB7) because most of the commercial photoinitiators have poor two-photon initiating efficiency in aqueous solutions. The binding ratio of BMVPC and CB7 was determined as 1:1 by isothermal titration calorimetry and quantum chemical calculation. The formation of the host-guest complex increases the two-photon absorption cross-section about five times, and improves the water solubility required as the photoinitiator for hydrogel fabrication. The BMVPC-CB7 inclusion complex was used as the one-component photoinitiator, and the polyethylene glycol diacrylate with promising biocompatibility was used as the hydrogel monomer to form the aqueous-phase photoresist system applied to two-photon polymerization microfabrication. A relatively low laser threshold of 4.5 mW, a high fabricating resolution of 180 nm, and the true three-dimensional (3D) fabricating capability in the aqueous solution have been obtained by using the as-prepared photoresist system. Finally, 3D engineering hydrogel scaffold microstructures with low toxicity and good biocompatibility have been fabricated and cocultured with living HeLa cells, which demonstrates the potential for further application in tissue engineering.
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Materiais Biocompatíveis , Hidrocarbonetos Aromáticos com Pontes/química , Carbazóis/química , Hidrogéis , Imidazóis/química , Lasers , Alicerces Teciduais/química , Materiais Biocompatíveis/química , Células HeLa , Humanos , Hidrogéis/síntese química , Hidrogéis/química , Microtecnologia , Polietilenoglicóis/química , Engenharia TecidualRESUMO
Porous titanium (Ti) and its alloys fabricated by additive manufacturing (AM) techniques have attractive potential for dental and bone defect repair fields. Understanding the relationship between cells and the surface of the as-built three-dimensional (3D) scaffold interactions is not only necessary for tissue engineering but also promising for improving the fabrication process in the manufacture of artificial implants by AM technology. In this study, we have aimed to investigate the cell behavior including adhesion and proliferation of fibroblasts (L929) on Ti-6Al-4 V scaffolds fabricated by the electron beam melting method. The porosities of Ti-6Al-4 V scaffolds are 0% (compact), 60%, and 70%, respectively. Different cell behaviors have been observed from all of the specimens after 4 and 8 days of cell incubation. The present result indicates that, besides the surface roughness, the surface topography of specimens should also be taken into consideration to investigate the interaction between implants and cells. Therefore, this study would provide several possibilities for improving the osteointegration functions of the manufactured porous metallic implants in orthopedic and dental applications.
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The biocompatibility of the three-dimensional (3D) hydrogel cell scaffolds that sodium hyaluronate (SH) and carboxymethyl chitosan (Chitosan) has been investigated. The minimum processing threshold of 2.94 mW and the feature line width of 80 nm have been obtained by the two-photon polymerization (TPP) technology using the as-prepared biocompatible photoresist. Through tuning the contents of the cross-linker in the hydrogel, the mechanical property of 3D hydrogel scaffold can be optimized to ensure the stability and affinity of scaffold. Furthermore, we have fabricated the SH and Chitosan assisted 3D hydrogel cell scaffolds and investigated the biocompatibility. This study provides a facile method to develop 3D biocompatible hydrogel cell scaffold, which would open up new avenues for the potential application in tissue engineering.
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In this study, two kinds of novel carbazole-based ethynylpyridine salts: 3,6-bis[2-(1-methylpyridinium)ethynyl]-9-pentyl-carbazole diiodide (BMEPC) and 3,6-bis[2-(1-methylpyridinium)ethynyl]-9-methyl-carbazole diiodide (BMEMC) have been employed as photosensitizers owing to their excellent antibacterial activity. These molecules possess symmetric A-π-D-π-A-type structures, which would bring in the unique optical properties. The inhibition zone measurement of a gradient concentration from 0 to 100 µM showed BMEPC and BMEMC photoinduced antibacterial activity against Escherichia coli. Diameters of zone of inhibition were up to 15 and 14 mm under laser irradiations. Under the exposure of the laser of 442 nm with a power density of 20 mW/cm2, the minimum inhibitory concentrations (MICs) of BMEPC on E. coli were between 3.5 and 6.9 µM and that of BMEMC were between 9.4 and 18.8 µM, respectively. In the dark experiments as a control, the MIC value is between 6.9 and 13.8 µM for BMEPC, whereas it is between 187.5 and 225.0 µM for BMEMC. By the comparison of the MIC values of BMEPC and BMEMC with laser irradiation and in dark, the laser-induced toxicity on bacteria is more evident, though both of the derivatives have dark toxicity. With the laser irradiation duration of 30 s and 10 min for BMEPC and BMEMC, respectively, the survival rate of E. coli approximates zero. An antibacterial mechanism has been proposed based on the electron paramagnetic resonance characterization, which indicates that a nitride radical is generated under laser irradiation. The carbazole-based ethynylpyridine photosensitizers would provide high potential for further applications in photodynamic therapy.
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The microtechnology of controlling stimuli-responsive biomaterials at micrometer scale is crucial for biomedical applications. Here, we report bovine serum albumin (BSA)-based three-dimensional (3D) microstructures with tunable surface morphology and pH-responsive properties via two-photon polymerization microfabrication technology. The laser processing parameters, including laser power, scanning speed, and layer distance, are optimized for the fabrication of well-defined 3D BSA microstructures. The tunable morphology of BSA microstructures and a wide range of pH response corresponding to the swelling ratio of 1.08-2.71 have been achieved. The swelling behavior of the microstructures can be strongly influenced by the concentration of BSA precursor, which has been illustrated by a reasonable mechanism. A panda face-shaped BSA microrelief with reversible pH-responsive properties is fabricated and exhibits unique "facial expression" variations in pH cycle. We further design a mesh sieve-shaped microstructure as a functional device for promising microparticle separation. The pore sizes of microstructures can be tuned by changing the pH values. Therefore, such protein-based microstructures with controllable morphology and pH-responsive properties have potential applications especially in biomedicine and biosensors.
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Flexible electrically conductive nanowires are now a key component in the fields of flexible devices. The achievement of metal nanowire with good flexibility, conductivity, compact and smooth morphology is recognized as one critical milestone for the flexible devices. In this study, a two-beam laser direct writing system is designed to fabricate AgNW on PET sheet. The minimum width of the AgNW fabricated by this method is 187 ± 34 nm with the height of 84 ± 4 nm. We have investigated the electrical resistance under different voltages and the applicable voltage per meter range is determined to be less than 7.5 × 103 V/m for the fabricated AgNW. The flexibility of the AgNW is very excellent, since the resistance only increases 6.63% even after the stretched bending of 2000 times at such a small bending radius of 1.0 mm. The proposed two-beam laser direct writing is an efficient method to fabricate AgNW on the flexible sheet, which could be applied in flexible micro/nano devices.
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We demonstrate the transition of lasing modes in the resonating cavity constructed by polystyrene opal photonic crystals and 7 wt. % tert-butyl Rhodamine B doped polymer film. Both single mode and multiple mode lasing emission are observed from the resonating cavity. The lasing threshold is determined to be 0.81 µJ/pulse for single mode lasing emission and 2.25 µJ/pulse for multiple mode lasing emission. The single mode lasing emission is attributed to photonic lasing resulting from the photonic bandgap effect of the opal photonic crystals, while the multiple mode lasing emission is assigned to random lasing due to the defects in the photonic crystals. The result would benefit the development of low threshold polymeric solid state photonic crystal lasers.
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Nanodiamond, which has a lattice defect, the energy band gap and good biocompatibility, is an ideal inorganic fluorescent imaging material for cells. However, the nanodiamond aggregation is not exactly suitable for cells' endocytosis if the size is too small or too big. Therefore, it has a profound meaning to modify the surface of nanodiamond and control the dispersion of nanodiamond aggregate. In this study, the surface of the detonated nanodiamond is modified into carboxylated nanodiamond by using the method of mixed acid oxidation. Then, the nanodiamond aggregates' dispersion in water is regulated by adjusting the pH, which is first discussed as a factor influencing the size of nanodiamond aggregation. This process further induces the corresponding change of the electrostatic force between nanoparticles, improves its applicability in the field of living cell fluorescence imaging.
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Diamante , Nanoestruturas , Imagem Óptica/métodos , Ácidos Carboxílicos/química , Células HeLa , Humanos , Concentração de Íons de Hidrogênio , Oxirredução , Propriedades de Superfície , ÁguaRESUMO
We demonstrate low threshold lasing oscillation in a photonic crystal (PhC) laser by using tert-butyl Rhodamine B (t-Bu-RhB) doped gain media. Lactonic t-Bu-RhB is synthesized to improve doping concentration in polymethylmethacrylate (PMMA) films, and then isomerized to the zwitterion form to achieve highly fluorescent gain medium. The t-Bu-RhB doped PMMA film is sandwiched by a pair of polystyrene colloidal crystals to construct a PhC resonating cavity. Single-mode laser oscillation at 592 nm is observed when the PhC resonating cavity is pumped by a Nd:YAG laser. The lasing threshold is 0.12 MW cm(-2) utilizing 6.9 wt% t-Bu-RhB doped PMMA films, which is only 1/60 of that with 3 wt% t-Bu-RhB doped PMMA films. The concentration-dependent lasing action is attributed to different gain factors of the t-Bu-RhB doped PMMA films. Furthermore, a spatially and spectrally coherent laser beam from the PhC resonating cavity is verified by exploring the far-field image and angular dependence of the lasing emission. The approach provides a facile and efficient strategy to reduce the lasing threshold for fabricating low threshold PhC lasers.