Fabrication of a micro-tip array mold using a micro-lens mask with proximity printing

In this study, a mold for a micro-tip array is fabricated using a microlens array mask with proximity exposure. The micro-tip array uses a microlens array mask with geometrical optics. Light passing through a microlens is focused at the focal points. There is microlens on the mask and the pattern that results from the light passing through the mask is directly projected onto the photoresist surface. A concave profile is developed using a positive photoresist and the remaining photoresist microstructures are formed after the development process. By changing the distance between the mask and the photoresist and the radius of curvature of the microlens, various tip shapes can be fabricated. The exposure gap is calculated using the microlens array mask and the geometry of the mold of micro-tip array is established using the irradiance absorption maps for the different levels. These methods respectively use the model of the positive photoresist and optical software. When electroforming a metallic micro-tip copy of the patterned photoresist, masters are created. The metal micro-tip array is used membrane probe card.     

Concave microlens array mold fabrication in photoresist using UV proximity printing

This paper presents a simple and effective method for fabricating a polydimethyl-siloxane (PDMS) microlens array with a high fill factor. The proposed method utilizes the UV proximity printing and photoresist replication methods. A concave microlens array mold is made using a printing gap in a lithography process. Optical UV light diffraction of UV light is used to deflect light away from the aperture edges to produce a certain exposure in the photo-resist material outside the aperture edges. This method can precisely control the geometric profile of a concave microlens array. The experimental results show that a concave micro-lens array can be formed automatically in photo-resist when the printing gap ranges from 240 to 720 μm. A high fill factor microlens array can be produced when the control pitch distance between the adjacent apertures of the concave microlens array is decreased to the aperture size.     

Voxel-based fabrication through material property mapping: A design method for bitmap printing

We present a bitmap printing method and digital workflow using multi-material high resolution Additive Manufacturing (AM). Material composition is defined based on voxel resolution and used to fabricate a design object with locally varying material stiffness, aiming to satisfy the design objective. In this workflow voxel resolution is set by the printer’s native resolution, eliminating the need for slicing and path planning. Controlling geometry and material property variation at the resolution of the printer provides significantly greater control over structure–property–function relationships. To demonstrate the utility of the bitmap printing approach we apply it to the design of a customized prosthetic socket. Pressure-sensing elements are concurrently fabricated with the socket, providing possibilities for evaluation of the socket’s fit. The level of control demonstrated in this study cannot be achieved using traditional CAD tools and volume-based AM workflows, implying that new CAD workflows must be developed in order to enable designers to harvest the capabilities of AM.     

New high fill-factor triangular microlens array fabrication method using UV proximity printing

A simple and effective method for fabricating a high fill-factor triangular microlens array using the proximity printing in lithography process is reported. The technology utilizes the UV proximity printing by controlling the printing gap between the mask and substrate. The designed approximate triangle microlens array pattern can be fabricated in photoresist. This is because to the UV light diffraction deflects away from the aperture edges and produces a certain exposure in photoresist material outside the aperture edges. This method can precisely control the geometric profile of a high fill-factor triangular microlens array. The experimental results showed that the triangular photoresist microlens array could be formed automatically when the printing gap ranged from 240 to 840 μm. The gapless triangular microlens array will be used to increase the luminance for the backlight module of liquid crystal displays. An erratum to this article can be found at     

A novel method for the fabrication of high-aspect ratio C-MEMS structures

A novel fabrication process was developed to create high aspect ratio (>10:1) carbon posts, all-carbon suspended bridges and wires, self-organized bunches of carbon posts, and carbon plates supported by carbon beams. The structures are all made from a two-step pyrolysis process with SU-8 photoresist as the starting material. In this paper we describe the fabrication of these various new C-MEMS structures and detail an important application of the high aspect ratio carbon posts arrays. The carbon post arrays can be reversible charged/discharged with Li ions, an application that may greatly impact the application of C-MEMS in three-dimensional microbatteries. Complex suspended C-MEMS structures, such as wires, plates, ribbons, and self-organized bunches of posts, were built. Methods to accurately and repeatedly fabricate all the above 3-D C-MEMS structures are given.     

Silicon shadow mask fabrication for patterned metal deposition with microscale dimensions using a novel corner compensation scheme

Pattern deposition of metals with controlled and microscale dimensions can be a challenging task if traditional photolithography is not a practical option. This is a particularly valid concern for the case of certain polymer substrates, which are gaining in importance in the microelectronics and related industries. Therefore, a novel design and process flow for batch fabricating low cost reusable silicon shadow masks was developed. Of note was the corner compensation scheme employed to avoid over-etching of the convex corners in the design. These shadow masks enabled deposition of metals or other suitable materials with feature sizes ranging from approximately 3 to 250 μm and were successfully utilized to form patterned metal heater lines and pads on various samples. The heaters, required for conducting thermal conductivity measurements of the underlying films/substrates using the three omega (3ω) method, showed resistance–temperature linearity, confirming theoretical estimates to within 0.2%. Moreover, the room temperature thermal conductivity of an amorphous SiO₂ film as well as a polyaniline thick film were measured, further validating the deposition through shadow mask technique.     

Large area mold fabrication for the nanoimprint lithography using electron beam lithography

The mold fabrication is a critical issue for the development of nanoimprint lithography as an effective low-cost and mass production process.This paper describes the fabrication process developed to fabricate the large area nanoimprint molds on the silicon wafers.The optimization of e-beam exposure dose and pattern design is presented.The overlayer process is developed to improve the field stitching accuracy of e-beam exposure,and around 10 nm field stitching accuracy is obtained.By means of the optimizatio...     

The fabrication of LIGA mask using photolithography and synchrotron radiation lithography

 The fabrication of LIGA mask is a very important step in LIGA process. Usually an intermediate mask with gold absorber pattern of 2 μm thickness is fabricated firstly using gold electroplating for absorber pattern in the resist structure written by Electron Beam (e-Beam), then the LIGA mask can be copied from the intermediate mask using synchrotron radiation lithography and gold electroplating. Recently, we use photolithography (instead of e-beam) to make the primary structure, and produce the intermediate mask with gold absorber pattern of 1.5 μm thickness produced by etching gold film with 1.5 μm thickness under the photoresist structure using Ar⁺. The LIGA mask with absorber pattern of 13 μm thickness is copied from the intermediate mask using synchrotron radiation lithography and gold electroplating. Received: 30 October 1995/Accepted: 9 December 1995     

面向模具陡峭区的接触式测量误差补偿方法

为了实现大型复杂曲面模具的加工与检测一体化,避免二次装卡误差问题,针对模具的陡峭曲面,利用基于UG二次开发的在机测量系统,提出合理的测量点选择及测量误差补偿方法。对陡峭曲面进行在机测量实验,通过与蓝光数码光栅三维扫描仪得到的测量结果进行比对,验证了该测量误差补偿方法在实际生产中的可行性,为大型复杂曲面模具的测量提供了一种高效、准确、低成本的测量系统。     

采用SU—8胶制作模具的工艺研究

主要描述了SU—8胶制造微流体芯片用模具的工艺研究。讨论了各工艺流程主要包括有前烘、中烘、光刻、显影等因素对模具的影响。提出了一个可供参考的模具制作工艺流程,对抗粘层工艺进行了讨论。另外,在模具制造过程中加入反应离子刻蚀(RIE)来提高SU—8与硅基底的粘附性。最终通过上述的工艺研究,成功制作出了应用于流体的模具,并制造成了微流控芯片。     

一种新型三维实体到标准工艺版图的转换方法

研究了一种准标准格式的三维实体文件的结构,在此基础上提出了三维实体到标准工艺版图的转换方法,并采用VC 编程语言开发了相应的转换接口.最后通过典型MEMS器件--微机械加速度计进行了验证,结果表明这种转换方法是切实可行的.     

Swelling of SU-8 structure in Ni mold fabrication by UV-LIGA technique

UV-LIGA technique is used to fabricate hot embossing mold of PMMA microfluidic chip. Pre-polished Ni plate serves as electroforming substrate and the micro channel is the only structure to be electroformed in the fabricated mold. The precision of the micro channel strongly depends on the process parameters. Experiments show that the width of micro channel varies with the electroforming time. With the electroforming time of 108, 140 and 160 min, the width of micro channel reduces to 89, 86 and 82% of patterned SU-8 mold respectively, which is caused by swelling of SU-8 in acidic, high temperature electroforming solution. This swelling is the key answer to the slope of the sidewalls of the electroformed structure. This study is beneficial to optimizing microfluidic chip mold design.     

A novel ant-based clustering algorithm using the kernel method

A novel ant-based clustering algorithm integrated with the kernel (ACK) method is proposed. There are two aspects to the integration. First, kernel principal component analysis (KPCA) is applied to modify the random projection of objects when the algorithm is run initially. This projection can create rough clusters and improve the algorithm’s efficiency. Second, ant-based clustering is performed in the feature space rather than in the input space. The distance between the objects in the feature space, which is calculated by the kernel function of the object vectors in the input space, is applied as a similarity measure. The algorithm uses an ant movement model in which each object is viewed as an ant. The ant determines its movement according to the fitness of its local neighbourhood. The proposed algorithm incorporates the merits of kernel-based clustering into ant-based clustering. Comparisons with other classic algorithms using several synthetic and real datasets demonstrate that ACK method exhibits high performance in terms of efficiency and clustering quality.     

A novel bonding method for fabrication of PMMA nanofluidic chip with low deformation of the nano-trenches

All PMMA-based nanofluidic chips are becoming increasingly important for biological and medical applications. To fabricate PMMA nanofluidic chips, the open nano-trenches should be sealed by thermal bonding method. However, the present thermal bonding method suffers from high deformation of nano-trenches due to PMMA softening near glass transition temperature. In this work, a novel bonding technique, based on acetone and ethanol (v:v, 8:2) treatment, is developed to adjust the Young’s modulus of PMMA in its surface layer. By optimizing nanoimprinting and bonding process, PMMA nanofluidic chip was fabricated without undesired nano-trench deformation. The integrity of the enclosed PMMA nanofluidic system was verified by a fluorescence filling experiment.     

A controllable liquid mold for fabrication of 3D spherical structures and arrays

This study presents a fabrication method for spherical or ellipsoidal structures, achieved by using a liquid mold in a controlled manner. In order to verify this method, the physical relationship between liquid drops and pre-cured PDMS mixture was investigated during fabrication by altering properties such as density, viscosity, and surface tension. The results show that the lateral capillary force plays a critical role in fabricating hollow dome-like structures in a well-arranged array format. The degree of sphere of the fabricated structures was theoretically examined and was consistent with experimental data. This method is useful for fabricating hollow spherical structures with easy-to-fabricate protocols, and is affordable for general laboratories not equipped with conventional clean room facilities. Standard molding techniques for spherical structures are commonly cumbersome and difficult, since the removal process of the spherical rigid mold from the structure is almost impossible, or destructive to the fabrication. The current fabrication method uses a liquid fabrication mold, therefore providing a noninvasive means of forming spherical structures in pre-cured polymeric mixtures for micro- and meso-scale level applications. This method is also potentially beneficial for producing dynamic culture arrays with a sufficient supply of cell media to maintain controlled cellular environments that can directly induce stem cell differentiation and proliferation.     

Prediction of laser solid freeform fabrication using neuro-fuzzy method

In this paper, a new application of a neuro-fuzzy method (ANFIS) to laser solid freeform fabrication (LSFF) is presented. The laser solid freeform fabrication process is a complex manufacturing technique that cannot be modeled analytically due to non-linear behaviours of the physical phenomena involved in the process. A neuro-fuzzy model is proposed to predict the clad height (coating thickness) as a function of laser pulse energy, laser pulse frequency, and traverse speed in a dynamic fashion. Four membership functions are assigned to be associated with each input of the model architecture. Experiments are performed to collect data for the training of the proposed network, and a set of unseen experimental data are also considered for the verification of the identified model. The effects of the assigned inputs on the clad height are discussed. The comparison between the experimental data and the model output shows promising results. The model can predict the process with an absolute error as low as 0.07%.     

A novel document ranking method using the discrete cosine transform

We propose a new spectral text retrieval method using the discrete cosine transform (DCT). By taking advantage of the properties of the DCT and by employing the fast query and compression techniques found in vector space methods (VSM), we show that we can process queries as fast as VSM and achieve a much higher precision.     

A novel graph-based clustering method using noise cutting

Recently, many methods have appeared in the field of cluster analysis. Most existing clustering algorithms have considerable limitations in dealing with local and nonlinear data patterns. Algorithms based on graphs provide good results for this problem. However, some widely used graph-based clustering methods, such as spectral clustering algorithms, are sensitive to noise and outliers. In this paper, a cut-point clustering algorithm (CutPC) based on a natural neighbor graph is proposed. The CutPC method performs noise cutting when a cut-point value is above the critical value. Normally, the method can automatically identify clusters with arbitrary shapes and detect outliers without any prior knowledge or preparatory parameter settings. The user can also adjust a coefficient to adapt clustering solutions for particular problems better. Experimental results on various synthetic and real-world datasets demonstrate the obvious superiority of CutPC compared with k-means, DBSCAN, DPC, SC, and DCore.     

A novel fabrication method of fiber-optical planar transmission sensors for monitoring pH in concrete structures

Monitoring concrete structures requires robust, long-term stable, and low-cost sensors. We introduce a new technique for producing a fiber-optical planar transmission sensor setup using a wafer saw for cutting the sensitive zone, which can monitor in situ pH in concrete. The sensitive zone of the fiber-optical sensor setup is filled with a sensing material, which color varies reversibly upon change of pH. Analyzing the characteristic changes in absorption of this material is done by a micro spectrometer. Our fabrication method is suited for industrial mass production because no cost-intensive adjustment of fibers is necessary. In this paper we will present beside our fabrication method the calibration of pH sensors produced with this method.     

A novel method for characterization of liquid transport through micro-wicking arrays

The existing methods for predicting/modeling the permeability of a wick structure involve the use of a capillary pressure model. Thus, the validity of the existing permeability models has not been verified independent of the capillary pressure. Here, for the first time, the permeability and capillary pressure of monoporous wick structures have been independently determined using a new experimental approach. In the new approach, the liquid mass flow rate against gravity is measured by testing the wick at its dryout threshold at different wicking lengths. The permeability and capillary pressure of the wick are then uniquely determined by curve fitting the wicking length-dependent mass flow data. The advantage of the developed method over Washburn’s rate of rise technique is that the current method yields both capillary pressure and permeability values while the former only returns the product of the two parameters. The permeability values obtained from the experiments were used to examine the accuracy of the existing permeability models.