钨丝微电极阵列的简易制备方法

本文提出了一种简易、低成本的钨丝微电极阵列制作工艺和方法.该方法采用MEMS工艺制作的玻璃模具实现钨丝阵列的精密有序排列,同时,在钨丝电极表面涂覆一层光敏性的聚酰亚胺作为绝缘层,结合"双面光刻"技术和电化学腐蚀技术实现电极位点大小和电极丝几何尺寸的精确控制.最后,通过注模、光刻制作SU-8固定座体完成钨丝微电极阵列的组装固定.整个制作工艺简单快速,且玻璃模具可重复使用,大大降低了制作成本.此外,本文还测试和评价了所制作微电极的表面形貌、电学性能以及生物相容性.     

纳米流体通道的制备及其应用研究进展EI北大核心CSCD

纳米流体是指流体在特征尺寸小于100 nm的通道或孔中流动呈现超快水运输、表面电荷控制离子传输等独特的物理行为。该现象的有效利用在生物、能源相关领域展现出巨大的潜力,因而引起人们的广泛关注。近年来,随着纳米流体通道制造技术的飞速发展,利用其进行能源转化取得了空前的增长。本文综述了纳米流体通道的主要制备方法,介绍基于纳米光刻、微电子机械系统技术(MEMS)、纳米材料三类常规制备策略以及其他非常规纳米流体通道制备方法,随后讨论了纳米流体通道在盐差能转换、刺激相应门控、离子检测、单分子传感、海水淡化领域的重要应用研究,最后,对当前利用纳米流体材料的制备方法及未来研究方向面临的挑战和机遇进行讨论,比如高成本、可靠性和稳定性有待提高等。     

Blue-phase templated fabrication of three-dimensional nanostructures for photonic applications

A promising approach to the fabrication of materials with nanoscale features is the transfer of liquid-crystalline structure to polymers. However, this has not been achieved in systems with full three-dimensional periodicity. Here we demonstrate the fabrication of self-assembled three-dimensional nanostructures by polymer templating blue phase I, a chiral liquid crystal with cubic symmetry. Blue phase I was photopolymerized and the remaining liquid crystal removed to create a porous free-standing cast, which retains the chiral three-dimensional structure of the blue phase, yet contains no chiral additive molecules. The cast may in turn be used as a hard template for the fabrication of new materials. By refilling the cast with an achiral nematic liquid crystal, we created templated blue phases that have unprecedented thermal stability in the range -125 to 125?°C, and that act as both mirrorless lasers and switchable electro-optic devices. Blue-phase templated materials will facilitate advances in device architectures for photonics applications in particular.     

Computer-aided process planning for assembly: generation of assembly operations sequence

Process planning for assembly requires a computerized representation and analysis of assembled products. In order to recommend a good sequence of assembly operations, the process planner needs to generate all such feasible sequences. This paper presents a methodology to consistently generate all feasible asssembly sequences with consideration for the various combinations of subassembly operations. The methodology is demonstrated on a real product. A practical method to reduce the number of feasible combinations generated is also demonstrated.     

The application of STEP-NC using agent-based process planning

Computer aided part programming is an information intensive activity, and provides an interesting area for the application of artificial intelligence, knowledge-based systems and recently for agent technologies. Intelligent software agents can behave and respond autonomously to set criteria. The flexibility of agents and their ability to make autonomous/cooperative decisions makes them an excellent tool in the development of future computer aided process planning systems. In addition, a new ISO standard for NC machine tool programming is emerging called ISO 14649, informally known as STEP-NC. This standard is aimed to replace the existing ISO 6983 (G&M code) standard, which has been in use since the first NC machine tools were developed in the 1950s. STEP-NC does not describe tool movements but uses a higher-level language to define operations known as Workingsteps. A new breed of intelligent controller is envisaged to determine optimized tool trajectories allowing advanced inter-operability and a bi-directional information flow which allows edits made at the machine to be fed back to the CAD/CAM model. This paper presents a STEP-NC compliant computational environment used to demonstrate agent-based process planning, resulting in the generation of STEP-NC code. The system comprises a multi-agent framework, where agents represent the individual features of the component and work independently and cooperatively to generate process plans for discrete component manufacture. This is demonstrated through a series of case study components which evaluate various feature interaction scenarios.     

A generative process planning system for parts produced by rapid prototyping

This paper presents a generative process planning system for parts produced by the rapid prototyping process (i.e. fused deposition modelling–FDM). The proposed process planning involves optimal selection of orientating the model with a proper support structure and then provides an intelligent slicing methodology, such as direct or adaptive, to minimise the built up time, keeping the geometry and cusp height errors in control. Pre- and post-slicing processes have been used to minimise the sliced data error. The Computer Aided Process Planning (CAPP) model has been arranged into five modules: orientation, support structure generation, slicing, path planning and Numerical Control (NC) program generation, and model build up. The CAPP model has been implemented in C language having a unique methodology consisting of 42 simplified steps. The CAPP model has been tested for several examples and shows satisfactory results.     

A simple method of microneedle array fabrication for transdermal drug delivery

Abstract

The outermost layer of skin, stratum corneum, being lipophilic limits the passive transport of hydrophilic and large molecular weight drugs. Microfabrication technology has been adapted to fabricate micron scale needles, which are minimally invasive, yet able to deliver the drugs across this barrier layer. In this study, we fabricated microneedles from a biocompatible polymer, namely, poly (ethylene glycol) diacrylate. A simple lithographical approach was developed for microneedle array fabrication. Several factors including polymerization time, ultraviolet light intensity and distance from light source were studied for their effects on microneedle formation. The microneedle length and tip diameter can be controlled by varying these factors. The microneedles were shown to be able to penetrate cadaver pig skin. Model drug rhodamine B was encapsulated in the range of 50 µg to 450 µg per microneedle array. The fabricated microneedles containing rhodamine B increased the permeability by four times than the control. Altogether, we demonstrated that the microneedle arrays can be fabricated through a simple single-step process and needles were mechanically strong to penetrate skin, increasing the permeability of encapsulated drug through skin.     

Application of knowledge-based artificial immune system (KBAIS) for computer aided process planning in CIM context

In the present era, several manufacturing philosophies like lean manufacturing, total quality management (TQM), etc., have the goal of providing a quality product at reduced cost. In this research paper the process planning problem of a CIM system has been discussed where minimisation of cost of the finished product is considered as the main objective. For determining the cost of the finished product, scrap cost, forgotten by most of the previous researchers, has been considered along with other costs like raw material cost, processing cost, etc. In the present environment of concurrent engineering, optimisation of process planning is an NP-hard problem. To solve this complex problem a noble search algorithm, known as knowledge-based artificial immune system (KBAIS) has been proposed. The nobility of the proposed algorithm is that the inherent capability of AIS has been gleaned and incorporated with the property of the knowledge base. In this problem, the power of knowledge has been used for three stages in the algorithm: initialisation, selection and hyper-mutation. To demonstrate the efficacy of the proposed KBAIS, a bench mark problem has been considered. Intensive computational experiments have also been performed on randomly generated datasets to reveal the supremacy of the proposed algorithm over other existing heuristics.     

Setup planning for machining the features of prismatic parts

This paper focus on the development of a formalized procedure for automatic generation of feasible setups and then to select an optimal setup plan for machining the features of a given prismatic part. The proposed work simultaneously considers the basic concepts of setup planning from both machining and fixturing viewpoints in order to formulate feasible setup plans. The tasks that are performed are: (a) identifying groups of features that can be machined in a single setup, (b) determining a suitable work piece orientation, i.e. the suitable datum planes for each setup, (c) determining all the feasible setup plans to machine the given set of features of prismatic parts, and (d) evaluating the feasible setup plans on the basis of technological (available tolerance) and economical conditions (total setup time). For the proposed work the authors have introduced four new concepts namely, ‘surface fit for location’, ‘primary group’ ‘secondary group’, and ‘eligible group’. The first concept plays an important role in the identification of suitable faces of the part for positioning, clamping and supporting. The other three help in clustering of features, which can be converted in to candidate setups.     

Methodology for set-up planning automation of turned parts

This paper presents an automatic set-up planning module integrated in a CAPP system for rotational parts to be machined on a lathe. The developed system determines the possible set-up combinations that are necessary for a complete machining of the part as well as the order of each set-up and the surfaces to be used for clamping the part. The applied methodology takes into consideration constraints such as the geometry of both the stock and the final part, the geometry and the capacity of the chuck, and the part tolerances. In general, these constraints allow the system to obtain several valid solutions for clamping the part. Some criteria based on the clamping force and the value of tolerances have been considered in order to establish a preference order among these solutions. Finally, the analysis of linked tolerances and the tool approach direction to each surface determine the sets of surfaces to be machined within each set-up. An example part is used in the course of the paper to illustrate conveniently the methodology, and two additional case studies prove that this methodology is adequate for the solution of real cases.     

蒸汽加热型双效溴化锂机组的计算机辅助设计

设计并介绍了一套用于蒸汽型双效溴化锂串、并联冷水机组的计算机辅助设计系统,简述了系统中各物性参数的获得方法,说明了系统中设计校核的方法,给出了程序计算结果,并与已知参考数据进行了比较。     

Integration and application of feature recognition and mould manufacturing planning navigating process

Plastic injection mould manufacturing is diverse and complex. Traditional mould manufacturing planning often relied on experience and techniques. Therefore, in order not to affect the operation or even cause some loss of the enterprises, geometry information of computer-aided design (CAD) should be converted into manufacturing information of computer-aided process planning (CAPP) and CAM for automatic feature recognition to shorten the lead time. This study is the secondary development in a CAD environment creating a network plastic injection mould manufacturing navigating system and CAD/CAPP for integration and application. As part design is feature-based, each processing step can be regarded as a feature. By applying the hybrid recognition technology of the graph-based approach, the rule-based approach and hint-based approach in the analysis of part feature appearances, it can automatically categorise all the manufacturing features of the part and convert them into corresponding processes. The CAPP developed in this study can convert the part manufacturing features into corresponding processes and plan the part process sequence according to the process priority constraint relations. As proved by the case studies, the use of CAPP in this study can reduce planning time by 87%. It can provide users with a reference regarding process sequence, and speed up the part planning progress. Coupled with the mould manufacturing navigating process, it can achieve automatic design and manufacturing.     

Design of PDMS microlenses bonded to a lab-CD chip for ELISA applications

A novel device comprising polydimethyl-siloxane (PDMS) microlenses bonded to a microfluidic compact disk (CD) is proposed for enzyme-linked immunosorbent assay (ELISA) applications. The PDMS microlenses were fabricated using a simple soft replica molding method and were bonded to the microfluidic CD using oxygen plasma treatment. A commercial software tool (ZEMAX) has been used to analyze the focal length of the microlens. A laser-induced fluorescence bio-detection system, consisting of the integrated microfluidic CD/PDMS microlenses and an optical detection module, was constructed and used to examine the enzymatic reaction of 3-(4-hydroxy) phenly propionic acid. The experimental results show that the PDMS microlens focusing effect yields a significant improvement in the intensity of the detected fluorescence signals. As a result, the proposed device represents an ideal solution for ELISAs and other high-sensitivity bio-detection applications.     

Capacity planning with sequential two-level time constraints in the back-end process of wafer fabrication

A time constraint is a queue-time boundary that is set between particular sequential operations to ensure final product yield. These time boundaries, called ‘sequential time constraints’, can be found in a series of operations on the back-end of wafer fabrication. Wafers exceeding the time constraints are traced through the fabrication process, but generally pass through the remaining processes. Nonetheless, it is a waste of capacity to continue processing wafers with unacceptable yield. Unfortunately, these unacceptable wafers cannot be identified before the wafer acceptance test using the current control policy. This work proposes a control rule for two-level time constraints with capacity planning methodology under this rule. Wafers exceeding the lower time constraints will be treated as normal wafers; however, once wafers exceed the upper time constraint, they will be scrapped immediately. In the capacity planning model, a GI/G/m queuing network is applied to determine the required number of machines. By pre-setting target yields, the rates of wafers being marked or scrapped can be controlled. Furthermore, a novel scheme–regarding machine failures as irregular customers–is introduced to describe the effect of service interruptions. The results show that the proposed control rule and capacity planning model can more effectively resolve the issues of sequential time constraints. Moreover, the results of the analysis indicate that the current capacity expansion policy of the semiconductor industry should be re-examined.     

Mechanically tunable aspheric lenses via additive manufacture of hanging elastomeric droplets for microscopic applications

Abstract

Mechanically deformable lenses with dynamically tunable focal lengths have been developed in this work. The fabricated five types of aspheric polydimethylsiloxane (PDMS) lenses presented here have an initial focal length of 7.0, 7.8, 9.0, 10.0 and 10.2 mm. Incorporating two modes of operation in biconvex and concave–convex configurations, the focal lengths can be tuned dynamically as 5.2–10.2, 5.5–9.9, 6.6–11.9, 6.1–13.5 and 6.6–13.5 mm respectively. Additive manufacturing was utilized to fabricate these five types of aspheric lenses (APLs) via sequential layering of PDMS materials. Complex structures with three-dimensional features and shorter focal lengths can be successfully produced by repeatedly depositing, inverting and curing controlled PDMS volume onto previously cured PDMS droplets. From our experiments, we empirically found a direct dependence of the focal length of the lenses with the amount (volume) of deposited PDMS droplets. This new mouldless, low-cost, and flexible lens fabrication method is able to transform an ordinary commercial smartphone camera into a low-cost portable microscope. A few microscopic features can be readily visualized, such as wrinkles of ladybird pupa and printed circuit board. The fabrication technique by successively applying hanging droplet and facile mechanical focal-length-tuning set-up can be easily adopted in the development of high-performance optical lenses.     

微结构三维形貌无损检测的双波段显微干涉技术

功能型微结构具有调控光场或调控电子导通等功能,一般包含具有规则的几何形状,基于深度和线宽的比值,可以将其区分为高/低深宽比微结构。目前对微结构的检测,多用有损检测中的扫描电镜（SEM）剖面成像技术,而产线上迫切需要用于监测与改进制作工艺的无损检测技术。本文系统总结了作者所在研究团队十余年在微结构三维形貌无损检测方面的低相干显微干涉技术进展,其中白光显微干涉仪用于超光滑表面、台阶、微光学元件、微机械元件等低深宽比微结构的三维形貌检测,近红外显微干涉仪用于硅基高深宽比微结构的三维形貌检测。文章阐述了两波段显微干涉系统的关键技术与典型样品的检测实例,结果表明：白光显微干涉仪和近红外显微干涉仪是两种高精度的无损检测仪器,前者检测高深宽比小于等于4,后者检测高深宽比大于等于20的微结构三维形貌,数据结果是可信的。显微干涉无损检测技术获取的三维形貌数据,将有效优化微结构的制造工艺,进一步提升有关器件的性能。     

Capacity requirements planning for twin Fabs of wafer fabrication

Based on the assumption of infinite capacity, a Capacity Requirements Planning System (CRPS) is developed for twin fabs of wafer fabrication. Several shared equipments exist only in one of the twin fabs linked by an Inter-Fab Material Handling System. CRPS consists of four major modules. WIP-Pulling Module pulls work-in-process (WIP) that is the closest to the end of the process route to meet the Master Production Schedule. Workload Accumulation Module then calculates the expected equipment loading in different time buckets. If WIP cannot meet the Master Production Schedule (MPS) requirement, new wafer lots need to be released. Wafer Release Time Module is used to determine the release time of new lots by evaluating their expected equipment loading at the twin fabs on various time buckets. According to the lot release time, Wafer Start Fab Module can be used to evaluate the expected loading for each of the twin fabs and determine the start fab to optimise the workload balance among these twin fabs on various days. Based on experimental design, simulation results show that CRPS can balance the equipment loading between the twin fabs with shared equipment, on various days, and across various equipments at various levels of demands.     

三维超材料制造技术现状与趋势

三维超材料是具有三维空间特定排布的亚波长人工周期结构,具有自然材料不具备的超常规物理性能。本文以三维超材料的电磁调控技术为线索,简要论述了近年来三维超材料在基础研究和制造工艺方面的研究现状;梳理了目前三维超材料的制造方法,包含印刷电路板及组装的方法、机械加工方法、3D打印技术、微纳制造工艺;选取电磁隐身罩、透镜天线、吸波器、柔性超材料等代表性应用类别,简述了三维超材料器件的电磁调控方法与实现手段,所涉及的超材料种类包括左手超材料、渐变折射率超材料、智能超材料等。基于目前三维超材料研究领域待解决的问题,对今后三维超材料的发展趋势进行了探讨。

     

Anisotropic multi-step etching for large-area fabrication of surface microstructures on stainless steel to control thermal radiation

Abstract

Controlling the thermal radiation spectra of materials is one of the promising ways to advance energy system efficiency. It is well known that the thermal radiation spectrum can be controlled through the introduction of periodic surface microstructures. Herein, a method for the large-area fabrication of periodic microstructures based on multi-step wet etching is described. The method consists of three main steps, i.e., resist mask fabrication via photolithography, electrochemical wet etching, and side wall protection. Using this method, high-aspect micro-holes (0.82 aspect ratio) arrayed with hexagonal symmetry were fabricated on a stainless steel substrate. The conventional wet etching process method typically provides an aspect ratio of 0.3. The optical absorption peak attributed to the fabricated micro-hole array appeared at 0.8 μm, and the peak absorbance exceeded 0.8 for the micro-holes with a 0.82 aspect ratio. While argon plasma etching in a vacuum chamber was used in the present study for the formation of the protective layer, atmospheric plasma etching should be possible and will expand the applicability of this new method for the large-area fabrication of high-aspect materials.