3D Printed Prisms with Tunable Dispersion for the THz Frequency Range

Here, we present a 3D printed prism for THz waves made out of an artificial dielectric material in which the dispersion can be tuned by external compression. The artificial material consists of thin dielectric layers with variable air spacings which has been produced using a fused deposition molding process. The material properties are carefully characterized and the functionality of the prisms is in a good agreement with the underlying theory. These prisms are durable, lightweight, inexpensive, and easy to produce.     

Mechanical Properties Tailoring of 3D Printed Photoresponsive Nanocellulose Composites

3D printing technologies allow control over the alignment of building blocks in synthetic materials, but compositional changes often require complex multimaterial printing steps. Here, 3D printable materials showing locally tunable mechanical properties are produced in a single printing step of Direct Ink Writing. These new inks consist of a polymer matrix bearing biocompatible photoreactive cinnamate derivatives and up to 30 wt% of anisotropic cellulose nanocrystals. The printed materials are mechanically versatile and can undergo further crosslinking upon illumination. When illuminating the material and controlling the irradiation doses, the Young's moduli can be adjusted between 15 and 75 MPa. Moreover, spatially controlled illumination allows patterning stiff geometries, resulting in 3D printed structures with segments of different mechanical properties tailoring the mechanical behavior under compression. The high design freedom implemented by 3D printing and photopatternability opens the venue to rapid manufacturing of devices for applications such as prosthetics or soft robotics where the 3D shapes and mechanical properties must be tailored for personalized load cases.     

3D Printed Fractal Metamaterials with Tunable Mechanical Properties and Shape Reconfiguration

Lattice metamaterials constructed by curved microstructures exhibit large stretchability and are promising in soft electronics and soft robotics. Fractal structures are particularly efficient in improving stretchability as it shows multiple-order uncurling. However, the development of fractal metamaterials is hindered by hierarchical structures and large deformations. In this study, a design framework combining experiments, hierarchical theoretical models, and finite element simulations is developed to program the mechanical behaviors of fractal metamaterials. For 3D printing, a digital design tool is developed to visualize the structure and automatically generate the manufacturing representations. Results show that large stretchability (≈360%), bionic stress–strain curve matching, and imperfection insensitivity can be programmed by tuning the geometric parameters. An integrated device of an electromyogram sensor embedded in an imperfection-insensitive fractal metamaterial that matches the J-shaped stress–strain curve of human skin is demonstrated. Light-emitting diode devices based on fractal metamaterial with shape reconfiguration are also presented. This st paves a new way to realize multifunctional soft devices using fractal metamaterials.     

3D打印氧化锆材料在红外探测器中的应用探索

杜瓦为红外焦平面探测器提供良好的低温工作环境以及光、机、电、热传输通道。其中冷台面支撑结构作为红外探测器的承载平台,承受设备运输、振动、冲击等作用,对支撑结构的强度提出了更高的要求。因此需要开发新型支撑结构以提高杜瓦的可靠性。根据红外探测器组件低传导漏热、高可靠性的需求,从宏观和微观的角度对不同的支撑结构材料进行分析,对比了两种成型工艺所制备的支撑结构对红外探测器设计制造的影响。与传统加工方式相比,采用数字光处理(Digital Light Procession, DLP)技术成型的氧化锆精度可达到±0.03 mm,与X射线衍射仪(X-Ray Diffractometer, XRD)衍射峰标准卡片符合。这说明其纯度较高,且该技术能缩短工艺时长,优化封装流程。     

3D Printable Ultra-Highly Porous and Mechanically Strong Foam Materials for Multiple Applications

Highly porous foam ceramics exhibit broad prospects for multifunctional applications. With the facile Pickering-based foaming technique, wet foams consisting of nanoparticles (NPs) may exhibit high strengths. However, they also experience linear shrinkages as high as 50% after drying and sintering process. Suitable solutions for improving this situation have not been found yet. This work develops a method for fabricating NP-made foam ceramics by tuning the interfacial chemistry of this Pickering system. Trace amounts of ethanol are used to adjust the adsorbing behavior of surfactants on the silica surface to enhance the energy of attachment of the Pickering systems. Combined with the altered capillary forces, the linear shrinkages of the foam ceramic are considerably lowered. The pore wall of the obtained foam ceramics can be tuned to either closed or open due to the “coffee ring” effect by adjusting the solid content and sintering temperature. The samples present high thermal insulating properties and high mechanical strength even the unsintered ones, which also show good stability in liquid environments. Combined with the direct ink writing (DIW) technique, these freely shaped materials with tunable pore structures can be readily exploited in tissue scaffolds, catalyst carriers, thermal insulators, battery electrodes, and liquid/gas filtration, etc.     

Self-Healing,Photothermal-Responsive,and Shape Memory Polyurethanes for Enhanced Mechanical Properties of 3D/4D Printed Objects

Additive manufacturing is a promising technology that can directly fabricate structures with complex internal geometries, which is barely achieved by traditional manufacturing. However, the mechanical properties of fused deposition modeling (FDM)-printed objects are inferior to those of conventionally manufactured products. To improve the mechanical properties of the printed products, a series of novel thermoplastic polyurethanes with self-healing properties, intrinsic photothermal effects, and excellent printability are designed and synthesized by introducing dynamic oxime–carbamate bonds and hydrogen bonds into the polymer chains. On-demand introduction of near-infrared (NIR) irradiation, direct heating, and sunlight irradiation enhances interfacial bonding strength and thus improve the mechanical properties of the printed product. Additionally, mechanical anisotropy of the printed products can be sophistically manipulated by regulating the self-healing conditions. Support-free printing and healing of damaged printed products are also achieved owing to the self-healing properties of the material. Moreover, the as-prepared materials exhibit shape-memory properties NIR irradiation or direct heating effectively triggers shape-memory recovery and demonstrates their potential in 4D printing by printing a man-like robot. This study not only provides a facile strategy for obtaining high-performance printed products but also broadens the potential applications of FDM technology in intelligent devices.     

Unique Electro‐Optical Properties of Liquid Crystals Designed for Molecular Optics

Antiferroelectric order has been known to exist in liquid crystals since more than a decade and is now an intensely studied field of research. The great application potential of antiferroelectric liquid crystals has especially been demonstrated in sophisticated flat‐panel display prototypes, which nevertheless have not yet reached manufacturing, due to the severe intrinsic problem of folds in the smectic layers, which drastically limit the achievable contrast, and which seem impossible to circumvent. By proper molecular design, we have developed and tested a new generic class of antiferroelectric materials that present an elegant solution to this problem. Their optical properties make them unique not only among liquid crystals but among electro‐optical materials in general. The design of this generic class, which we call orthoconic, also gives an illustrative example of the physical meaning of the addition of tensorial properties. Normal surface‐stabilized antiferroelectrics are optically positive biaxial crystals, with an effective optic axis along the smectic layer normal. The surprising optical property of the corresponding orthoconic antiferroelectric can be formulated as a theorem: When the tilt directions in adjacent smectic layers are made perpendicular to each other, the material becomes negatively uniaxial with the optic axis lying perpendicular to the smectic layer normal. The electro‐optic effect in such a material is based on the fact that the optic axis can be switched between three mutually orthogonal directions, corresponding to zero, negative, or positive values of the applied electric field.     

光盘系统中的光纤飞行头应用

叙述了光纤飞行头在计算机存储器中应用的可能性 ,指出由于带光阻透镜的单模光纤 ,其质量轻、光路简单、易于调整及可并行输入等优点 ,可以在光盘驱动器中发挥作用。介绍的光纤飞行头跟踪、伺服的原理和读写光路 ,有可能在光盘驱动器上使用     

光交换技术在光纤网中的应用

本文对光纤网中光交换技术的发展、现状进行了概括回顾与展望。从有利于集成化的角度,重点讨论了光选通元件、光双稳器件、网络结构,以及空分交换、波分交换在光纤网中的应用。     

三维CAD在空间光学遥感仪器中的应用

随着空间技术的发展,空间光学仪器对机械结构的要求越来越精细和复杂,如何快速、高效、准确地设计出高质量的产品已成为当务之急．三维设计以其高效、直观、信息量大、便于分析等优点越来越引起人们的关注。本文以SolidWorks软件为平台,以某光机扫描仪为例,介绍了利用三维CAD技术设计空间光学仪器机械结构的方法和思路。     

Customizable and Reconfigurable Surface Properties of Printed Micro-objects by 3D Direct Laser Writing via Nitroxide Mediated Photopolymerization

Photoactivated Reversible Deactivation Radical Polymerization (RDRP) technologies have emerged very recently in the field of 3D printing systems especially at the macroscale in vat-photopolymerization-based processes such as digital light processing (DLP). Contrary to conventional free radical photopolymerization, photoRDRP in 3D printing leads to 3D objects with living character and thus confers them the unique ability to be post-modified after fabrication. While 3D direct laser writing (3D DLW) by two photon polymerization has become a standard for fabrication of complex 3D micro-objects, the use of RDRP and its associated benefits has so far been under-investigated at that scale. Herein, a photoresist suitable for 3D DLW based on nitroxide mediated photopolymerization (NMP2) is developed. The photopolymerization efficiency for fabrication of micro-structures and their subsequent post-modification are investigated regarding the laser power and the wavelength of excitation. Moreover, highly tunable, precise, and successive surface patterning of 2D and 3D multi-material microstructures are demonstrated thanks to the spatial and temporal control offered by the photo-induced post-modification. This work highlights new directions to be explored in order to accelerate the adoption of RDRP in 3D printing based on photopolymerization.     

Synthesis,Optical and Photoluminescence Properties of Cu-Doped Zno Nano-Fibers Thin Films: Nonlinear Optics

Different concentrations of copper-doped zinc oxide thin films were coated on a glass substrate by sol–gel/spin-coating technique. The structural properties of pure and Cu-doped ZnO films were characterized by different techniques, i.e., atomic force microscopy (AFM), photoluminescence and UV–Vis-NIR spectroscopy. The AFM study revealed that pure and doped ZnO films are formed as nano-fibers with a granular structure. The photoluminescence spectra of these films showed a strong ultraviolet emission peak centered at 392 nm and a strong blue emission peak cantered at 450 nm. The optical band gap of the pure and copper-doped ZnO thin films calculated from optical transmission spectra (3.29–3.23 eV) were found to be increasing with increasing copper doping concentration. The refractive index dispersion curve of pure and Cu-doped ZnO film obeyed the single-oscillator model. The optical dispersion parameters such as E _o , E _d , and \(n_{{\infty }}^{2}\) were calculated. Further, the nonlinear refractive index and nonlinear optical susceptibility were also calculated and interpreted.     

Feasibility and Characterization of Common and Exotic Filaments for Use in 3D Printed Terahertz Devices

Recent years have seen an influx of applications utilizing 3D printed devices in the terahertz regime. The simplest, and perhaps most versatile, modality allowing this is Fused Deposition Modelling. In this work, a holistic analysis of the terahertz optical, mechanical and printing properties of 17 common and exotic 3D printer filaments used in Fused Deposition Modelling is performed. High impact polystyrene is found to be the best filament, with a useable frequency range of 0.1–1.3 THz, while remaining easily printed. Nylon, polylactic acid and polyvinyl alcohol give the least desirable terahertz response, satisfactory only below 0.5 THz. Interestingly, most modified filaments aimed at increasing mechanical properties and ease of printing do so without compromising the useable terahertz optical window.     

Investigation and Development of 3D Printed Conventional Shape Compact UWB-DRAs for Societal Applications

Wireless Personal Communications - The potential of polylactic acid (PLA) material as an ultra-wide band (UWB)-dielectric resonator antenna (DRA) created by 3D-printing technique are described in...     

Properties of Building and Plastic Materials in the THz Range

We present measurements of the frequency dependent refractive index and absorption coefficient of a variety of common building and plastic materials between 100 and 1000 GHz. Accurate knowledge of the material parameters is indispensable for the modeling of bound media propagation phenomena including single and multiple reflections, transmission, diffraction and scattering effects. These models are for example required for a reliable channel simulation to investigate signal propagation in future wireless communication systems operating with Gigabit data rates at frequencies above 100 GHz. Also, the measured material parameters can be used for the investigation and development of THz system components.     

Low-Voltage and High-Responsivity Germanium Bipolar Phototransistor for Optical Detections in the Near-Infrared Regime

Germanium (Ge) bipolar phototransistors with high-responsivity performance are demonstrated using a low-temperature selective Ge epitaxy process. Large photocurrent and optical response enhancement are achieved over a conventional p-i-n Ge photodetector, which is predominantly attributed to the current gain induced by transistor actions. When illuminated with a photon wavelength of 1.55 mum , a Ge phototransistor shows a large responsivity of ~ 2.0 A/W for a low operating bias VA of 1.0 V. Optical measurement results further show that good photoresponse could be achieved for a spectral range of 1.31-1.62 mum, making such a device a very promising option for optical detections in the near-infrared (including L -band) wavelength regime.     

自适应光学系统光学部分的计算机模拟

利用相位屏（PS）方法通过软件模拟大气湍流,进而研究了自适应光学（AO）系统中哈特曼一夏克（H—S）波前传感器的计算机模拟技术。使用基于Zernike多项式的模式法重构波前,验证了模拟方法的可行性,完成了AO系统光学部分的计算机模拟。     

Ultraprecise 3D Printed Graphene Aerogel Microlattices on Tape for Micro Sensors and E-Skin

3D printed graphene aerogels hold promise for flexible sensing fields due to their flexibility, low density, conductivity, and piezo-resistivity. However, low printing accuracy/fidelity and stochastic porous networks have hindered both sensing performance and device miniaturization. Here, printable graphene oxide (GO) inks are formulated through modulating oxygen functional groups, which allows printing of self-standing 3D graphene oxide aerogel microlattice (GOAL) with an ultra-high printing resolution of 70 µm. The reduced GOAL (RGOAL) is then stuck onto the adhesive tape as a facile and large-scale strategy to adapt their functionalities into target applications. Benefiting from the printing resolution of 70 µm, RGOAL tape shows better performance and data readability when used as micro sensors and robot e-skin. By adjusting the molecular structure of GO, the research realizes regulation of rheological properties of GO hydrogel and the 3D printing of lightweight and ultra-precision RGOAL, improves the sensing accuracy of graphene aerogel electronic devices and realizes the device miniaturization, expanding the application of graphene aerogel devices to a broader field such as micro robots, which is beyond the reach of previous reports.     

A Subtractive Photoresist Platform for Micro‐ and Macroscopic 3D Printed Structures

The selective removal of structural elements plays a decisive role in 3D printing applications enabling complex geometries. To date, the fabrication of complex structures on the microscale is severely limited by multistep processes. Herein, a subtractive photoresist platform technology that is transferable from microscopic 3D printing via direct laser writing to macroscopic structures via stereolithography is reported. All resist components are readily accessible and exchangeable, offering fast adaptation of the resist's property profile. The micro‐ and macroprinted structures can be removed in a facile fashion, without affecting objects based on standard photoresists. The cleavage is analyzed by time‐lapse optical microscopy as well as via in‐depth spectroscopic assessment. The mechanical properties of the printed materials are investigated by nanoindentation. Critically, the power of the subtractive resist platform is demonstrated by constructing complex 3D objects with flying features on the microscale.