Two-photon polymerization lithography for imaging optics

Optical imaging systems have greatly extended human visual capabilities,enabling the observation and understanding of diverse phenomena.Imaging technologies span a broad spectrum of wavelengths from x-ray to radio frequencies and impact research activities and our daily lives.Traditional glass lenses are fabricated through a series of complex processes,while polymers offer versatility and ease of production.However,modern applications often require complex lens assemblies,driving the need for miniaturization and advanced designs with micro-and nanoscale features to surpass the capabilities of traditional fabrication methods.Three-dimensional(3D)printing,or additive manufacturing,presents a solution to these challenges with benefits of rapid prototyping,customized geometries,and efficient production,particularly suited for miniaturized optical imaging devices.Various 3D printing methods have demonstrated advantages over traditional counterparts,yet challenges remain in achieving nanoscale resolutions.Two-photon polymerization lithography(TPL),a nanoscale 3D printing technique,enables the fabrication of intricate structures beyond the optical diffraction limit via the nonlinear process of two-photon absorption within liquid resin.It offers unprecedented abilities,e.g.alignment-free fabrication,micro-and nanoscale capabilities,and rapid prototyping of almost arbitrary complex 3D nanostructures.In this review,we emphasize the importance of the criteria for optical performance evaluation of imaging devices,discuss material properties relevant to TPL,fabrication techniques,and highlight the application of TPL in optical imaging.As the first panoramic review on this topic,it will equip researchers with foundational knowledge and recent advancements of TPL for imaging optics,promoting a deeper understanding of the field.By leveraging on its high-resolution capability,extensive material range,and true 3D processing,alongside advances in materials,fabrication,and design,we envisage disruptive solutions to current challenges and a promising incorporation of TPL in future optical imaging applications.

Isotropic sintering shrinkage of 3D glass-ceramic nanolattices:backbone preforming and mechanical enhancement

There is a perpetual pursuit for free-form glasses and ceramics featuring outstanding mechanical properties as well as chemical and thermal resistance.It is a promising idea to shape inorganic materials in three-dimensional(3D)forms to reduce their weight while maintaining high mechanical properties.A popular strategy for the preparation of 3D inorganic materials is to mold the organic–inorganic hybrid photoresists into 3D micro-and nano-structures and remove the organic components by subsequent sintering.However,due to the discrete arrangement of inorganic components in the organic-inorganic hybrid photoresists,it remains a huge challenge to attain isotropic shrinkage during sintering.Herein,we demonstrate the isotropic sintering shrinkage by forming the consecutive–Si–O–Si–O–Zr–O–inorganic backbone in photoresists and fabricating 3D glass–ceramic nanolattices with enhanced mechanical properties.The femtosecond(fs)laser is used in two-photon polymerization(TPP)to fabricate 3D green body structures.After subsequent sintering at 1000℃,high-quality 3D glass–ceramic microstructures can be obtained with perfectly intact and smooth morphology.In-suit compression experiments and finite-element simulations reveal that octahedral-truss(oct-truss)lattices possess remarkable adeptness in bearing stress concentration and maintain the structural integrity to resist rod bending,indicating that this structure is a candidate for preparing lightweight and high stiffness glass–ceramic nanolattices.3D printing of such glasses and ceramics has significant implications in a number of industrial applications,including metamaterials,microelectromechanical systems,photonic crystals,and damage-tolerant lightweight materials.

Femtosecond-laser direct writing 3D micro/nano-lithography using VIS-light oscillator

Here we report a femtosecond laser direct writing(a precise 3D printing also known as two-photon polymerization lithography) of hybrid organic-inorganic SZ2080^(TM)pre-polymer without using any photo-initiator and applying ~100 fs oscillator operating at 517 nm wavelength and 76 MHz repetition rate. The proof of concept was experimentally demonstrated and benchmarking 3D woodpile nanostructures, micro-scaffolds, free-form micro-object “Benchy” and bulk micro-cubes are successfully produced. The essential novelty underlies the fact that non-amplified laser systems delivering just 40-500 p J individual pulses are sufficient for inducing localized cross-linking reactions within hundreds of nanometers in cross sections. And it is opposed to the prejudice that higher pulse energies and lower repetition rates of amplified lasers are necessary for structuring non-photosensitized polymers. The experimental work is of high importance for fundamental understanding of laser enabled nanoscale 3D additive manufacturing and widens technology’ s field of applications where the avoidance of photo-initiator is preferable or is even a necessity, such as micro-optics, nano-photonics, and biomedicine.

基于Ag-PDMS复合导电材料的微流控芯片3D电极的制备

提出一种利用Ag粉和聚二甲基硅氧烷(Polydimethylsiloxane,PDMS)制成的复合材料加工微流控芯片3D电极的方法。选取导电性良好的银粉作为填料物,透明性良好和生物兼容的PDMS作为基体。将Ag颗粒表面改性后,用超声法、机械共混法相结合的方法与PDMS混合加工形成一种新型Ag-PDMS复合导电材料。分析了Ag粉的形貌、粒径、填料比例与复合材料电阻率的关系,结果表明当选取粒径为1μm片状Ag颗粒作为填料物,填料质量分数为86%时,Ag-PDMS复合导电材料的导电性能最好。最后利用软光刻方法,经过曝光、显影、填充、固化和剥离等过程,制备了3D电极。实验证明,该方法可以成功制备Ag-PDMS复合导电材料微流控芯片3D电极,对微流控芯片电极的制备有重要意义。

基于3-D打印技术的新型微波/毫米波无源波导器件

综述了近年来基于多种3-D打印工艺的微波直至太赫兹频段无源波导器件的发展研究现状,并介绍了作者所在小组研制的多个基于立体光刻3-D打印工艺的滤波器(包括基于新型高Q值单模和双模球形腔体谐振器的X频段带通滤波器以及基于裂缝波导和紧凑片上结构的W频段带通滤波器).这些滤波器射频性能的测量与仿真结果吻合良好.与相同形状的铜制器件相比,采用非金属材料的3-D打印器件的重量减轻了80%以上,并保持了优良的射频性能.

紫外厚胶光刻技术在3-D MEMS电感中的应用

研究了紫外厚胶光刻技术在三维微机械电感中的应用。实验用负性光刻胶SU-8构造了三维微机械电感的胶结构模型,并对光刻胶的工艺条件进行了研究。结果表明,负性光刻胶SU-8的光敏性好,形成的胶结构侧墙较陡直,能够实现较大的深宽比,为结构复杂的三维微机械电感的制作提供了保证。

Laser additive manufacturing of Si/ZrO_(2)tunable crystalline phase 3D nanostructures

The current study is directed to the rapidly developing field of inorganic material 3D object production at nano-/micro scale.The fabrication method includes laser lithography of hybrid organic-inorganic materials with subsequent heat treatment leading to a variety of crystalline phases in 3D structures.In this work,it was examined a series of organometallic polymer precursors with different silicon(Si)and zirconium(Zr)molar ratios,ranging from 9:1 to 5:5,prepared via sol-gel method.All mixtures were examined for perspective to be used in 3D laser manufacturing by fabricating nano-and micro-feature sized structures.Their spatial downscaling and surface morphology were evaluated depending on chemical composition and crystallographic phase.The appearance of a crystalline phase was proven using single-crystal X-ray diffraction analysis,which revealed a lower crystallization temperature for microstructures compared to bulk materials.Fabricated 3D objects retained a complex geometry without any distortion after heat treatment up to 1400℃.Under the proper conditions,a wide variety of crystalline phases as well as zircon(ZrSiO_(4)-a highly stable material)can be observed.In addition,the highest new record of achieved resolution below 60 nm has been reached.The proposed preparation protocol can be used to manufacture micro/nano-devices with high precision and resistance to high temperature and aggressive environment.

Transition Dipole, Charge Transfer, and Electron-hole Coherence in Two-photon Absorption： Visualizations with Two Dimensional Site and Three Dimensional Cube Representations

The developed visualization methods of two dimensional （2D） site and three dimensional （3D） cube representations have been performed to show the orientation of transition dipole, charge transfer, and electron-hole coherence in two-photon absorption （TPA）. The 3D cube representations of transition density can reveal visually the orientation and strength of transition dipole moment, and charge different density show the orientation of charge transfer in TPA. The 2D site representation can reveal visually the electron-hole coherence in TPA. The combination of 2D site and 3D cube representations provide clearly inspect into the charge transfer process and the contribution of excited molecular segments for TPA.

Combining two-photon lithography with laser ablation of sacrificial layers:A route to isolated 3D magnetic nanostructures

Three-dimensional(3D)nanostructured functional materials are important systems allowing new means for intricate control of electromagnetic properties.A key problem is realising a 3D printing methodology on the nanoscale that can yield a range of functional materials.In this article,it is shown that two-photon lithography,when combined with laser ablation of sacrificial layers,can be used to realise such a vision and produce 3D functional nanomaterials of complex geometry.Proof-of-principle is first shown by fabricating planar magnetic nanowires raised above the substrate that exhibit controlled domain wall injection and propagation.Secondly,3D artificial spin-ice(3DASI)structures are fabricated,whose complex switching can be probed using optical magnetometry.We show that by careful analysis of the magneto-optical Kerr effect signal and by comparison with micromagnetic simulations,depth dependent switching information can be obtained from the 3DASI lattice.The work paves the way for new materials,which exploit additional physics provided by non-trivial 3D geometries.

Femtosecond laser 3D printed micro objective lens for ultrathin fiber endoscope

The most important optical component in an optical fiber endoscope is its objective lens.To achieve a high imaging performance level,the development of an ultra-compact objective lens is thus the key to an ultra-thin optical fiber endoscope.In this work,we use femtosecond laser 3D printing to develop a series of micro objective lenses with different optical designs.The imaging resolution and field-of-view performances of these printed micro objective lenses are investigated via both simulations and experiments.For the first time,multiple micro objective lenses with different fields of view are printed on the end face of a single imaging optical fiber,thus realizing the perfect integration of an optical fiber and objective lenses.This work demonstrates the considerable potential of femtosecond laser 3D printing in the fabrication of micro-optical systems and provides a reliable solution for the development of an ultrathin fiber endoscope.

Generating Microstructures with Highly Variable Mechanical Performance using Two-Photon Lithography and Thiol-ene Photopolymerization

In this study,we investigate the effect of the exposure dose on the mechanical property of the photoresins generated with acrylate self-polymerization and thiol-ene polymerization.The results indicate that the mechanical performance of the thiol-ene photoresin is highly depended on the exposure dose during the solidification process.With 350-fold exposure dose change,the stiffness of the thiol-ene photoresin reached more that 700-fold change compare to 14-fold of the acrylate photoresin.We developed a TPL photoresist based on our results and show the capability to fabricate microstrucutres with high resolution and variable mechanical performances using this method.

Fabrication of opaque and transparent 3D structures using a single material via twophoton polymerisation lithography

Two-photon polymerisation lithography enables the three-dimensional(3D)-printing of high-resolution micron-and nano-scale structures.Structures that are 3D-printed using proprietary resins are transparent and are suitable as optical components.However,achieving a mix of opaque and transparent structures in a single optical component is challenging and requires multiple material systems or the manual introduction of ink after fabrication.In this study,we investigated an overexposure printing process for laser decomposition,which typically produces uncontrollable and random‘burnt’structures.Specifically,we present a printing strategy to control this decomposition process,realising the on-demand printing of opaque or transparent structures in a single lithographic step using a single resin.Using this method,opaque structures can be printed with a minimum feature size of approximately 10μm,which exhibit<15%transmittance at a thickness of approximately 30μm.We applied this process to print an opaque aperture integrated with a transparent lens to demonstrate an improved imaging contrast.

Ultrasonic signal detection based on Fabry–Perot cavity sensor

Acoustic/ultrasonic sensors are devices that can convert mechanical energy into electrical signals.The Fabry–Perot cavity is processed on the end face of the double-clad fiber by a two-photon three-dimensional lithography machine.In this study,the outer diameter of the core cladding was 250μm,the diameter of the core was 9μm,and the microcavity sensing unit was only 30μm.It could measure ultrasonic signals with high precision.The characteristics of the proposed ultrasonic sensor were investigated,and its feasibility was proven through experiments.Its design has a small size and can replace a larger ultrasonic detector device for photoacoustic signal detection.The sensor is applicable to the field of biomedical information technology,including medical diagnosis,photoacoustic endoscopy,and photoacoustic imaging.

Two-photon lithography for 3D magnetic nanostructure fabrication

Ferromagnetic materials have been utilized as recording media in data storage devices for many decades. The confinement of a material to a two-dimensional plane is a significant bottleneck in achieving ultra-high recording densities, and this has led to the proposition of three-dimensional （3D） racetrack memories that utilize domain wall propagation along the nanowires. However, the fabrication of 3D magnetic nanostructures of complex geometries is highly challenging and is not easily achieved with standard lithography techniques. Here, we demonstrate a new approach to construct 3D magnetic nanostructures of complex geometries using a combination of two-photon lithography and electrochemical deposition. The magnetic properties are found to be intimately related to the 3D geometry of the structure, and magnetic imaging experiments provide evidence of domain wall pinning at the 3D nanostructured junction.

Small-world networks of neuroblastoma cells cultured in three-dimensional polymeric scaffolds featuring multi-scale roughness

Understanding the mechanisms underlying cell-surface interaction is of fundamental importance for the rational design of scaffolds aiming at tissue engineering,tissue repair and neural regeneration applications.Here,we examined patterns of neuroblastoma cells cultured in three-dimensional polymeric scaffolds obtained by two-photon lithography.Because of the intrinsic resolution of the technique,the micrometric cylinders composing the scaffold have a lateral step size of^200 nm,a surface roughness of around 20 nm,and large values of fractal dimension approaching 2.7.We found that cells in the scaffold assemble into separate groups with many elements per group.After cell wiring,we found that resulting networks exhibit high clustering,small path lengths,and small-world characteristics.These values of the topological characteristics of the network can potentially enhance the quality,quantity and density of information transported in the network compared to equivalent random graphs of the same size.This is one of the first direct observations of cells developing into 3D small-world networks in an artificial matrix.

EUV Lithography: State-of-the-Art Review

Although several years delayed than its initial plan, extreme UV lithography (EUVL) with 13.5nm wavelength has been finally implemented into high volume manufacture (HVM) of mainstream semiconductor industry since 2018. With the delivery and installation of ASML EUV scanners in those giant Fab players like Samsung, TSMC and Intel, EUV lithography is becoming a sort of industry standard exposure metrology for those critical layers of advanced technology nodes beyond 7nm. Although ASML NXE EUVL scanner is the only commercialized EUV exposure system available on the market, its development is the concentration of all essence from worldwide industrial and academic collaboration. It is becoming more and more important not only for fab runners but also for main stream fabless design houses to understand and participate the progress of EUVL. In this review, working principles, module structures and technical challenges have been briefly discussed regarding each EUV subsystem, including light source, reflection mirrors and system, reticle module as well as photoresist development. EUV specific issues of light intensity, defectivity within reflection system, line edge roughness (LER) and mask 3D effects have been focused respectively and promising solutions have been summarized as well.

Ice lithography for 3D nanofabrication

Nanotechnology and nanoscience are enabled by nanofabrication. Electron-beam lithography, which makes 2 D patterns down to a few nanometers, is one of the fundamental pillars of nanofabrication.Recently, significant progress in 3 D electron-beam-based nanofabrication has been made, such as the emerging ice lithography technology, in which ice thin-films are patterned by a focused electronbeam. Here, we review the history and progress of ice lithography, and focus on its applications in efficient 3 D nanofabrication and additive manufacturing or nanoscale 3 D printing. The finest linewidth made using frozen octane is below 5 nm, and nanostructures can be fabricated in selected areas on non-planar surfaces such as freely suspended nanotubes or nanowires. As developing custom instruments is required to advance this emerging technology, we discuss the evolution of ice lithography instruments and highlight major instrumentation advances. Finally, we present the perspectives of 3 D printing of functional materials using organic ices. We believe that we barely scratched the surface of this new and exciting research area, and we hope that this review will stimulate cutting-edge and interdisciplinary research that exploits the undiscovered potentials of ice lithography for 3 D photonics, electronics and 3 D nanodevices for biology and medicine.

微机械制造中的三维立体光刻加工技术

文章介绍了微机械和微机电系统制造的一种重要方法%D三维立体光刻技术方法的基本原理、加工技术及其应用。同时还介绍了立体光刻技术结合抗腐蚀层、牺牲层工艺加工微器件的原理、方法和应用。

应用三维线算法的SU-8胶光刻过程模拟

采用二维法向量作为分量,加权求和近似得到三维网格点上的单位法向量,将经典的二维线算法改进为三维形式。综合SU-8胶光刻过程中衍射、吸收率随光刻胶深度的变化及交联显影等各种效应,应用该三维线算法对SU-8化学放大胶进行光刻过程三维建模。该模型对被加工表面演化过程的模拟较为精确,可在实际应用中对SU-8胶的光刻模拟结果进行有效预测。

微加速度传感器的新进展

本文介绍了微加速度传感器的最新发展,单向微硅加速度传感器,三维集成微加速度传感器系统,微型集成惯性测量平台系统等。还介绍了最新的微加速度传感器和集成微加速度传感器的制造工艺技术。