Artificial Defect Engineering in Three‐Dimensional Colloidal Photonic Crystals

Artificial defect engineering in 3D colloidal photonic crystals is of paramount importance in terms of device applications. Over the past few years, we have carried out a great deal of research on introducing artificial defects, including point, line, and planar defects, in 3D colloidal photonic crystals by using “bottom‐up” self‐assembly in combination with “top‐down” micromachining techniques. In this Feature Article, we summarize our research results regarding the engineering of artificial defects in self‐assembled 3D photonic crystals, along with other important research breakthroughs in the literature. The significant advancements in the engineering of defects as reviewed here together with the encouraging reports on the fabrication of perfect colloidal crystals without unwanted defects will collectively lead to technological applications of self‐assembled 3D photonic crystals in the near future.     

LiNbO3／SiO2凝胶玻璃的非等温结晶动力学研究

利用差热分析和Ｘ衍射分析对ＬｉＮｂＯ３／ＳｉＯ２凝胶玻璃的非等温结晶动力学进行了研究。利用修正的ＪＭＡ方程直线计算了ＬｉＮｂＯ３和石英的析晶活化能、磷石英的相变活化能和频率因子，根据峰形指数计算了Ａｖｒａｍｉ结晶指数。ＬｉＮｂＯ３的结晶活化能为１４２ｋＪ／ｍｏｌ，ＬｉＮｂＯ３和石英晶体的生长过程受表面或界面控制。最后对凝胶玻璃的析晶难易和稳定性进行了分析。     

Fabrication and Characterization of Two‐Photon Polymerized Features in Colloidal Crystals

The fabrication and characterization of two‐photon polymerized features written within and outside of colloidal crystals is presented. Two‐photon polymerization (TPP) response diagrams are introduced and developed to map the polymerization and damage thresholds for features written via modulated beam rastering. The use of tris[4‐(7‐benzothiazol‐2‐yl‐9,9‐diethylfluoren‐2‐yl)phenyl]amine (AF‐350) as an initiator for TPP is demonstrated for the first time and TPP response diagrams illustrate the polymerization window. These diagrams also demonstrate that the polymerization behavior within and outside of colloidal crystals is similar and electron microscopy reveals nearly identical resolution. Fluorescence confocal microscopy further enables visualization of non‐self‐supporting, three‐dimensional TPP features within self‐assembled photonic crystals. Finally, microspot spectroscopy is collected from a two‐photon feature written within a colloidal crystal and this is compared with simulation.     

Growth and Structural Characterization of Spherical Silicon Crystals Grown from Polysilicon

The growth process for spherical silicon crystals using melting and recrystallization of polysilicon powder and polysilicon granules is investigated and the structural properties of the fabricated silicon spheres are characterized. The recrystallization conditions that influence the crystallinity of the spheres are studied. It is shown by means of defect delineation that crystalline structures are obtained when the melt is solidified at temperatures above 1400°C. The results of electron backscattering confirm the formation of single-grain structures. When solidification takes place at temperatures below 1400°C, double- and multiple-grain structures start to form. The concentration of impurities during the recrystallization of the spheres, monitored by secondary-ion mass spectroscopy, show that the rate of impurity removal from the crystalline phase is much lower than predicted by segregation at the melt–solid interface, which is attributed to the nonequilibrium conditions in the solidification process.     

Direct Ink Writing of 3D Functional Materials

The ability to pattern materials in three dimensions is critical for several technological applications, including composites, microfluidics, photonics, and tissue engineering. Direct‐write assembly allows one to design and rapidly fabricate materials in complex 3D shapes without the need for expensive tooling, dies, or lithographic masks. Here, recent advances in direct ink writing are reviewed with an emphasis on the push towards finer feature sizes. Opportunities and challenges associated with direct ink writing are also highlighted.     

Cover Picture: Direct Ink Writing of 3D Functional Materials (Adv. Funct. Mater. 17/2006)

The direct ink writing of three‐dimensional functional materials is detailed in the Feature Article by Lewis on p. 2193. The left side of the cover image displays schematic images that show the conversion of a direct‐write polymer woodpile to a silicon hollow‐woodpile structure. The 3 × 3 image matrix showcases the resulting silicon photonic crystal (center) surrounded by a higher‐magnification view of a representative hollow silicon feature (ca. 1 μm in diameter). The figure was prepared by F. Garcia‐Santamaria, G. M. Gratson, and P. V. Braun. The ability to pattern materials in three dimensions is critical for several technological applications, including composites, microfluidics, photonics, and tissue engineering. Direct‐write assembly allows one to design and rapidly fabricate materials in complex 3D shapes without the need for expensive tooling, dies, or lithographic masks. Here, recent advances in direct ink writing are reviewed with an emphasis on the push towards finer feature sizes. Opportunities and challenges associated with direct ink writing are also highlighted.     

TIPS-pentacene crystalline thin film growth

The crystalline film growth of TIPS-pentacene thin films by confined solution deposition is investigated. The crystalline thin films grow dendritic in the initial stage and continue to grow to elongated plate-like crystals when the solution is deposited in a confined space in-plane. The majority of the thin film, containing smaller thin crystals, is formed within the first 10 s after depositing the solution and continues to grow in minutes to millimeter sized single crystals. By atomic force microscopy we show that impurities are expelled by the growing crystals and clusters accumulate at step edges on the surface of the larger crystals. The influence of crystal thickness and orientation on the electronic transport in field-effect transistors is studied, and shows an optimum performance for devices with thin elongated crystals that are aligned parallel to the electric field between the source–drain electrodes.     

基于 CDIO 教育理念的自动化课程的改革与实践

CDIO,即构思(conceive)、设计(design)、实施(implement)、运作(operate),是以现代工业产品从构思、研发到运行乃至终结废弃的全生命周期为蓝本的、旨在培养学生的工程能力的一种方法。工科专业如何转变教育模式以适应国家经济高速发展的的需要,成为迫切要解决的问题。本文选用自动化专业的一门主干课程为研究对象,将该理念贯穿在课程学习的全过程,运用CDIO教育模式对该课程的教与学进行探讨和实践,提出一条新的工程教育模式,使学生在实际动手能力、独立创新能力、团队合作能力方面有所提高。