利用紫外光刻技术进行SU8胶的研究

SU 8光刻胶优异的性能在MEMS技术的发展重得到了广泛的应用 ,已经成为MEMS研究中必不可少的方法之一。SU 8光刻胶能够进行厚度达毫米的结构研究工作 ,另一方面SU 8结构具有很好的侧面垂直结构 ,通过控制工艺参数 ,能够获得满意的SU 8胶结构。SU 8光刻胶已应用于LIGA技术的标准化掩模制造工艺和一些器件的研究工作。在SU8胶研究过程中 ,克服了许多技术难题 ,使得这一技术能够应用到实际的需要中。     

Grain Boundary Diffusion Hardening in Potassium Sodium Niobate-Based Ceramics with Full Gradient Composition and High Piezoelectricity

Reducing mechanical losses and suppressing self-heating are critical characteristics for high-power piezoelectric applications. For environmentally friendly Pb-free piezoelectric ceramics, traditional acceptor doping or annealing treatments have successfully improved the mechanical quality factor (Q_m) based on a ceramic matrix with a poor piezoelectric coefficient (d₃₃<100 pC/N). Nevertheless, a ceramic with high Q_m and d₃₃ values has not been reported owing to the inverse relationship between Q_m and d₃₃. Herein, a novel hardening method called grain boundary diffusion is used to develop Pb-free potassium sodium niobate ceramics, where Q_m increased by more than two-fold (from 51 to 132) and a high d₃₃ value (d₃₃ = 360 pC/N) is maintained. Significantly, d₃₃ retained 98% of its initial value after 180 days, exhibiting improved aging stability. The established properties are associated with the formation of the core-shell microstructure and the full gradient composition distribution using structural characterizations and phase-field simulations, where the core maintains a high d₃₃ and the shell provides a hardening effect. The novel hardening effect in piezoelectric materials, known as grain boundary diffusion hardening, highlights the enhancement of the mechanical quality factor with high piezoelectricity, providing a new paradigm for the design of functional materials.     

Assembly and Characterizations of Bifunctional Fluorescent and Magnetic Microneedles With One Decade Length Tunability

This report presents the fabrication of bifunctional magnetic and fluorescent microneedles (µNDs) made of a ternary mixture of magnetic nanoparticles (NPs), quantum dots (QDs), and polyelectrolyte. The assembly relies on the electrostatic complexation of negatively charged NPs with positively charged polymer strands and is controlled by the charge ratio between the nanoparticle building blocks and the polymer mortar. The resulting 1D objects can be actuated using an external magnetic field and can be imaged using fluorescence microscopy, thanks to the fluorescent and superparamagnetic properties inherited from their NP constituents. Using a combination of core and surface characterizations and a state‐of‐the‐art image analysis algorithm, the dependence of the brightness and length on the ternary composition is thoroughly investigated. In particular, statistics on hundreds of µNDs with a range of compositions show that the µNDs have a log‐lormal length distribution and that their mean length can be robustly tuned in the 5–50 µm range to match the relevant length scales of various applications in micromixing, bioassays or biomechanics.     

Ortho‐ vs Bay‐Functionalization: A Comparative Study on Tetracyano‐Terrylenediimides

In this paper n‐type semiconductors synthesized via selective fourfold cyanation of the ortho‐ and bay‐positions (2,5,10,13‐ and 1,6,9,14‐positions respectively) of teyrrylenediimides are reported. A detailed study about the impact of the diverse functionalization topologies on the optoelectronic properties, self‐organization from solution, solid‐state packing, and charge carrier transport in field‐effect transistors is presented. The ortho‐substitution preserves the planarity of the core and favors high order in solution processed films. However, the strong intermolecular interactions lead to a microstructure with large aggregates and pronounced grain boundaries which lower the charge carrier transport in transistors. In contrast, the well‐soluble bay‐functionalized terrylenediimide forms only disordered films which surprisingly result in n‐type average mobilities of 0.17 cm²/Vs after drop‐casting with similar values in air. Processing by solvent vapor diffusion enhances the transport to 0.65 cm²/Vs by slight improvement of the order and surface arrangement of the molecules. This mobility is comparable to highest n‐type conductivities measured for solution processed PDI derivatives demonstrating the high potential of TDI‐based semiconductors.     

TC4合金激光熔覆WC-12Co涂层

利用扫描电镜和能谱仪对TC4合金表面激光熔覆WC-12Co熔覆区的组织和成分进行了研究。结果表明,熔覆层组织为多边形的大颗粒WC和其间分布的细小的树枝晶。TC4合金表面激光熔覆WC-12Co可以实现涂层与基体之间良好的冶金结合,激光熔覆层的最高硬度达1200HV。     

基于聚焦离子束注入的微纳加工技术研究

提出了聚焦离子束注入（focused ion beam implantation,FIBI）和聚焦离子束XeF2气体辅助刻蚀（gas assisted etching,GAE）相结合的微纳加工技术。通过扫描电镜观察FIBI横截面研究了聚焦离子束加工参数与离子注入深度的关系。当镓离子剂量大于1.4×1017ion/cm2时,聚焦离子束注入层中观察到均匀分布、直径10～15nm的纳米颗粒层。以此作为XeF2气体反应的掩膜,利用聚焦离子束XeF2气体辅助刻蚀（FIB-GAE）技术实现了多种微纳米级结构和器件加工,如纳米光栅、纳米电极和微正弦结构等。结果表明该方法灵活高效,很有发展前途。     

粉末冶金制品激光熔覆的组织与性能研究

对常规烧结的铁基粉末冶金制品进行表面激光熔覆处理 ,用 SEM和 TEM对熔覆样品的显微组织进行了观察 ,测试并分析了其孔隙度和显微硬度 ,结果表明 :熔覆层组织为 γ M7C3 共晶 ,表层硬度显著提高而整体孔隙度降低。     

Electric‐Field‐Controlled Alignment of Rod‐Shaped Fluorescent Nanocrystals in Smectic Liquid Crystal Defect Arrays

Periodic micro‐arrays of straight linear defects containing nanoparticles can be created over large surface areas at the transition from the nematic to smectic‐A phase in a nanoparticle–liquid crystal (LC) composite material confined under the effect of conflicting anchoring conditions (unidirectional planar vs normal) and electric fields. Anisomeric dichroic dye molecules and rod‐shaped fluorescent semiconductor nanocrystals (dot‐in‐rods) with large permanent electric dipole and high linearly polarized photoluminescence quantum yield align parallel to the local LC molecular director and follow its reorientation under application of the electric field. In the nano‐sized core regions of linear defects, where the director is undefined, anisotropic particles align parallel to the defect whereas spherical quantum dots do not show any particular interaction with the defect. Under application of an electric field, ferroelectric semiconductor nanoparticles in the core region align along the field, perpendicular to the defect direction, whereas dichroic dyes remain parallel to the defect. This study provides useful insights into the complex interaction of anisotropic nanoparticles and anisotropic soft materials such as LCs in the presence of external fields, which may help the development of field‐responsive nanoparticle‐based functional materials.     

Selective Functionalization of Microstructured Surfaces by Laser‐Assisted Particle Transfer

Microcavity arrays represent millions of different reaction compartments to screen, for example, molecular interactions, exogenous factors for cells or enzymatic activity. A novel method is presented to selectively synthesize different compounds in arrays of microcavities with up to 1 000 000 cavities per cm². In this approach, polymer microparticles with embedded pre‐activated monomers are selectively transferred into microcavities with laser radiation. After particle patterning, heating of the particle matrix simultaneously leads to diffusion and coupling of the monomers inside each microcavity separately. This method exhibits flexibility, not only in the choice of compounds, but also in the choice of particle matrix material, which determines the chemical reaction environment. The laser‐assisted selective functionalization of microcavities can be easily combined with the intensively growing number of laser applications for patterning of molecules and cells, which is useful for the development of novel biological assays.