Thin film formation on non-planar surface with use of spray coating fabrication

This paper presents a three-dimensional microfabrication and integration technology for MEMS smart materials that utilizes a spray coating method. Spray coating is shown to be most effective for additional deposition on non-planar surfaces. PZT films were formed both on flat and uneven surfaces at a thickness of about 1 μm. Perovskite structures were formed with suitable heat treatment and ferroelectric P-E hysteresis loop was also obtained. This paper is the first report from our group and other researchers on the deposition of smart materials for MEMS using a spray coating method. Spray coating has been proposed as an effective three-dimensional coating method which can be used to deposit piezoelectrics, pyroelectrics, magnetics, etc. for sensors and actuators. The hydrophilic and hydrophobic properties between the substrate surface and ejected liquid are most essential process factors in the spray coating method for improving the film growth conditions.     

Zone electrophoresis of proteins in poly(dimethylsiloxane) (PDMS) microchip coated with physically adsorbed amphiphilic phospholipid polymer

The zone electrophoresis of protein in poly(dimethylsiloxane) (PDMS) microchip coated with the physically adsorbed amphiphilic phospholipid polymer (PMMSi) was investigated. PMMSi was composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) and 3-(methacryloyloxy) propyltris (trimethylsiloxy) silane (MPTSSi) units in a random fashion. The membrane of PMMSi can be formed on the PDMS surface by a simple and quick dip-coating method. The membrane showed high hydrophilicity and good stability in water, as determined by contact angle measurement, fourier-transformed infrared absorption by attenuated total reflection (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS) analysis. High suppression of protein adsorption to the PDMS surface and reduction in electroosmotic flow (EOF) were achieved by PMMSi coating due to an increase of hydrophilicity, and a decrease of the ζ-potential on the surface of PDMS. For zone electrophoresis, the PMMSi30 containing 30 % hydrophilic MPC was the most suitable molecular design in terms of the stability of the coated membrane on PDMS surface. The average value of EOF mobility of PDMS microchip coated with PMMSi30 was 1.4 × 10^?4 cm² V^?1 s^?1, and the RSD was 4.1 %. Zone electrophoresis of uranine was further demonstrated with high repeatability and reproducibility. Separation of two FITC-labeled proteins (BSA and insulin) was performed with high efficiency and resolution compared with non-treated PDMS microchip.     

Solvent-free surface modification by initiated chemical vapor deposition to render plasma bonding capabilities to surfaces

A versatile solvent-free method for surface modification of various materials including both metals and polymers is described. Strong irreversible bonds were formed when substrates modified by initiated chemical vapor deposition (iCVD) of poly(1,3,5-trivinyltrimethylcyclotrisiloxane) or poly(V3D3) and exposed to an oxygen plasma were brought into contact with plasma-treated poly(dimethylsiloxane) (PDMS). The strength of these bonds was quantified by burst pressure testing microfluidic channels in the PDMS. The burst pressures of PDMS bonded to various coated substrates were in some cases comparable to that of PDMS bonded directly to PDMS. In addition, porous PTFE membrane coated with poly(V3D3) was successfully bonded to a PDMS microfluidic device and withstood pressures of over 300 mmHg. Bond strength was shown to correlate with surface roughness and quality of the bond between the coating and substrate. This work paves a methodology to fabricate microfluidic devices that include a specifically tailored membrane. Furthermore, the bonded devices exhibited hydrolytic stability; no dramatic change was observed even after immersion in water at room temperature over a period of 10 days.     

可印刷柔性应变传感器的制作及其对 人体运动行为监测研究

该文主要研究了导电浆料 PS@Ag/PDMS 的流变特性与印刷性,以聚苯乙烯微球表面镀 银(PS@Ag)的核壳结构粒子为导电填料,与聚二甲基硅氧烷(PDMS)预聚物及其固化剂复合配制 PS@Ag/PDMS 导电浆料,采用丝网印刷技术与旋涂工艺制备得到 PDMS-PS@Ag/PDMS-PDMS 三明治结构柔性应变传感器。柔性应变传感器在人体运动行为中的实时监测结果显示,该传感器在手肘关节与膝盖关节的弯曲——伸展循环运动中的相对电阻变化率分别高达约 0.75 0.50,展现出较高的可拉伸柔性、灵敏度及一致性,在人体运动行为监测中具有广阔的应用前景。     

Computer controlled galvanizing

In the galvanizing process zinc is coated onto the steel strip to inhibit rusting. Excess zinc is used to ensure that the finished product exceeds coating quality standards. Reducing the excess coating to a minimum while maintaining product quality can significantly reduce a company's zinc bill.A computer based coating-mass control system, installed on a galvanizing line, has reduced zinc consumption by thirteen percent, saving in excess of one million dollars annually. The same system has been installed in a zincalume line with similar results.The most significant time constant in the process is the transport delay between coatingmass control and measurement. Feedforward control, using a simple model and a table of adapted constants, compensate for this during major changes in process conditions. Feedback control, using a self-adapting linear incremental model, maintains the coating-mass within range during steady-state conditions.     

Spray rendering

Spray rendering provides a framework for creating and experimenting with different visualization techniques. The name spray rendering is derived from the metaphor of using a virtual spray can to paint data sets. Varying the type of paint in the can highlights data in different ways. Spray rendering is not limited to the paint metaphor, however. Other useful metaphors include a flashlight and a probe. Thus, spray rendering refers to the localized nature of the visualization algorithms and the manner in which the algorithms are sent to the data sets. We gain several advantages by looking at visualization algorithms in this way, including extensibility, grid independence, and ability to handle large data sets. This article presents the benefits, conceptual design, issues and directions of spray rendering     

AdaBoost算法在喷码图像识别的应用

喷码在印刷中使用比较普遍,其识别通常采用模板匹配的方法,但是由于喷码常出现误差,为模板匹配方法识别带来难度。AdaBoost是一个建构准确分类器的学习算法,文中将此算法应用于喷码图像的识别,不仅提高了识别的准确率,速度也更为理想。     

Patterning of carbon nanotube films on PDMS using SU-8 microstructures

In this paper, we propose a simple and low-cost fabrication technique for patterning carbon nanotube (CNT) films on polydimethylsiloxane (PDMS), which can be used in flexible sensors and electronics. We demonstrate CNT patterning on both recessed and flat PDMS surfaces using a standard photolithography method. By this proposed technique, we were able to fabricate a CNT film, having a high flexibility and good conductivity, on a PDMS surface. A CNT pattern with a minimum feature resolution of 150 μm was obtained using the proposed fabrication technique. The sheet resistance of the CNT film on the PDMS surface was determined to be in the 100–280 Ω/sq range. The thickness and resultant resistivity of the CNT film can be easily controlled by controlling just the spray duration. Furthermore, the gauge factor of the proposed device is higher than that of metal and it increases as the thickness of the CNT film increases.     

Optimization of tool change timing in a nut forming process using genetic algorithms

In this study, we consider an optimization problem arising from tool change scheduling of a nut forming process. The process has nine punches with different life spans. The objective of the study is to optimize the tool change timing of the nine punches in order to maximize the production yield. The punch life spans can be extended by means of Ti coating, but coated punches are more expensive. We also evaluate whether it is worth using coated punches. A cost model is developed for the nut forming process. In the developed cost model, we consider the reliability of the nine punches, the periods taken for changing punches, scrap cost and production yield. The cost function for the process is complex, and is difficult to be solved using conventional optimization methods. Therefore, genetic algorithms are used to solve the problems. We have developed our own genetic algorithms using Java programs and applied the developed genetic algorithms to provide solutions to the optimization problem.     

Rapid replication of polymeric and metallic high aspect ratio microstructures using PDMS and LIGA technology

This paper present a method of rapid replication of polymeric high aspect ratio microstructures (HARMs) and a method of rapid reproduction of metallic micromold inserts for HARMs using polydimethylsiloxane (PDMS) casting and standard LIGA processes. A high aspect ratio (HAR) metallic micromold insert, featuring a variety of test microstructures made of electroplated nickel with 15:1 height-to-width ratio for 300 μm microstructures, was fabricated by the standard LIGA process using deep X-ray lithography (DXRL). A 10:1 mixture of pre-polymer PDMS and a curing agent were cast onto the HAR metallic micromold insert, cured and peeled off to create reverse images of the HAR metallic micromold insert in PDMS. In addition to the replication of polymeric HARMs, replicated PDMS HARMS were coated with a metallic sacrificial layer and electroplated in nickel to reproduce another metallic micromold insert. This method can be used to rapidly and massively reproduce HAR metallic micromold inserts in low cost mass production manner without further using DXRL.     

The fabrication and property of a novel coated out-of-plane microneedle arrays

The efficiency of transdermal drug delivery (TDD) is often undermined by stratum corneum of skin. In this paper, a novel design and fabricating process was developed to coat microneedles (MNs). Testing results of facture strength of the MNs demonstrated that the Ni coated microneedle can meet the mechanical requirement for practical TDD applications. Dip-coating experiment demonstrated that it was practical to load baicalin onto the surfaces of the MNs. The amount of loaded drug was increased simply by increasing times of dip-coating operation. It was also demonstrated that upon coated by HPMC or PVP, drug can be released from the MNs in a more sustainable manner. Coating solution had great impact on drug releasing rate, indicating that the required drug concentration can be achieved by proper coating solution.     

A computer controlled spray system

A computer-controlled spray system is described that is used to control the application of thermal protection coatings to the Space Shuttle Exxternal Tank. The hardware and software requirements of the system as a manufacturing process are presented. The Spray Control System controls all turntables, elevators and spraying equipment used by the caoting process. Coatings are applied in a barber pole fashion, the turntable rotation, elevator vertical travel, and motions and functions of the spraying equipment being coordinated by the process control software.     

基于声表面波实现数字微流体的产生

数字微流体的产生是压电材料为基片的微流控芯片进行微流分析的前提,报道了在压电基片上应用声表面波技术产生数字微流体的方法.在128°旋转Y切割X传播方向的LiNbO3基片上集成PDMS微通道,在微通道出口一侧为经疏水处理的铝薄片,注射泵产生恒定流量的微流体经PDMS微通道到达铝薄片并聚集,当聚集的微流体体积足够大时,微流体克服表面张力作用下滑到达压电基片,并在中心频率为27.7 MHz叉指换能器激发的声表面波作用下输运,实现微流体的数字化.同时,理论分析了微流体在铝薄片表面上受力状况,并以水为实验对象,进行微流体数字化实验.结果表明,声表面波作用下能精确产生微升量级数字微流体,为压电微流控芯片提供了一种新的微流体引入方法.     

Hybrid replication development for construction of polymeric devices

The combination of poly(dimethyl)siloxane (PDMS) replica molding, hot-embossing of poly(methyl)methacrylate (PPMA) and PDMS membrane transfer has been explored for the construction of a pneumatically-actuated, multi-levelled polymeric microvalve. The critical part of the process, bonding of the three polymeric levels, has been demonstrated. It involves bonding of PDMS to PDMS using two different methods, one with oxygen plasma treatment and heat treatment, and the other one with PDMS as glue, whereas PDMS was bonded to PMMA using a commercial primer. A method for replicating PDMS parts in large number was also described.Nicolas Alamagny and Sylvain Lefèbvre are thanked for their help in the microvalve fabrication and hot embossing respectively. The cleanroom staff is also greatly acknowledged for their help throughout this work. Michel de Labachelerie and Michel Froelicher are also thanked for helpful discussions on the microfluidic aspect of the project and the hot embossing respectively.     

Soft lithography replication based on PDMS partial curing

In this paper, a partial curing technique is presented. Its aim is to enable the soft lithography replication process for the case requiring usage of PDMS mold. Through controlling the curing time during molding step, the liquid PDMS prepolymer in original status, which will later constitute the device substrate, can be partially polymerized as well as solidified. As a result, not only can the structural pattern in the mold be successfully transferred into the device layer, but also the spontaneous adhesive interaction between these two PDMS parts happening during curing can be effectively limited within very low level, thus largely facilitating the demoulding process. Based on this process, several devices have been successfully developed and high fidelity pattern transfer capability has also been demonstrated. Comparing with the most commonly used treatments such as silanization, the presented method demonstrates easier operation and better user-friendly interface advantages.     

Fabrication of steel roller imprinting molds through adapting conventional planar micro fabrication tools

A soft lithography process has been developed to transfer a pattern directly from a flat PDMS stamp to a stainless steel cylindrical substrate using an SAM ink, without any need to physically attach the stamp to a roller. The process uses standard semiconductor wafer processing equipment, along with specially designed elements to adapt to the cylindrical substrates. The entire process can be applied to batch processing and thus can be directly applied to manufacturing. This technique was demonstrated by fabricating a steel herringbone journal bearing with a diameter of 1.5 mm. The HGJB is an important element which is used for high-speed rotating spindles of electro-mechanical systems such as hard disk drives, CD-Rom drives, and DVD drives in the consumer electronics industry. In this case, the pattern had a dimension of 85 microns and depth of 3 microns. Features as deep as ten microns and as narrow as two microns have been also demonstrated.     

Process modeling,simulation, and paint thickness measurement for robotic spray painting

An algorithm and a computer program are developed for modeling of the spray painting process, simulation of robotic spray painting, and off‐line programming of industrial robots for painting of curved surfaces. The computer program enables the user to determine the painting strategies, parameters, and paths which will give the desired paint thickness. Surface models of the parts that are to be painted are obtained by using a computer‐assisted design (CAS) software. Models of relatively simple surfaces are formed by using the surface generation tools of the CAD software. For parts with more complex surfaces, point data related to the part is collected by using a laser scanner, and this data is used to form the CAD model of the part surface. The surface is then divided into small triangular elements and centroid coordinates, and unit normals of the elements are determined. Surface data together with the spray distance, painting velocity, and paint flow rate flux are used for simulation of the process and paint thickness analysis. Paint flow rate flux is determined experimentally by using different spray gun settings and painting parameters. During the experiments flat surfaces are painted by using a single painting stroke of the gun. Then, paint thickness measurements are made on the surfaces. It is observed that besides the technical specifications of the spray gun, air and paint nozzles, and paint needle, basic settings like paint tank pressure, spray air pressure, and gun needle‐valve position affect paint cone angle and paint flow rate, which finally characterize the spray painting process. For that reason, settings and parameters should be changed and the painting process should be simulated until an acceptable paint thickness distribution is obtained for the part that is going to be painted. The robot program is then generated in the robot's programming language. Paint thickness distribution on the painted surface is determined by measuring the thicknesses using the robot and the CAD model of the part surface. The thicknesses are measured at the centroids of the surface elements. A measurement probe of the coating thickness measurement gauge is attached to the wrist of the robot by using a feedback/safety adapter designed and manufactured for this purpose. © 2000 John Wiley & Sons, Inc.     

Stamp-and-stick room-temperature bonding technique for microdevices

Multilayer MEMS and microfluidic designs using diverse materials demand separate fabrication of device components followed by assembly to make the final device. Structural and moving components, labile bio-molecules, fluids and temperature-sensitive materials place special restrictions on the bonding processes that can be used for assembly of MEMS devices. We describe a room temperature "stamp and stick (SAS)" transfer bonding technique for silicon, glass and nitride surfaces using a UV curable adhesive. Alternatively, poly(dimethylsiloxane) (PDMS) can also be used as the adhesive; this is particularly useful for bonding PDMS devices. A thin layer of adhesive is first spun on a flat wafer. This adhesive layer is then selectively transferred to the device chip from the wafer using a stamping process. The device chip can then be aligned and bonded to other chips/wafers. This bonding process is conformal and works even on surfaces with uneven topography. This aspect is especially relevant to microfluidics, where good sealing can be difficult to obtain with channels on uneven surfaces. Burst pressure tests suggest that wafer bonds using the UV curable adhesive could withstand pressures of 700 kPa (7 atmospheres); those with PDMS could withstand 200 to 700 kPa (2-7 atmospheres) depending on the geometry and configuration of the device.     

Tool path planning for compound surfaces in spray forming processes

Spray forming is an emerging manufacturing process. The automated tool planning for this process is a nontrivial problem, especially for geometry-complicated parts consisting of multiple freeform surfaces. Existing tool planning approaches are not able to deal with this kind of compound surface. This paper proposes a tool-path planning approach which optimizes the tool motion performance and the thickness uniformity. There are two steps in this approach. The first step partitions the part surface into flat patches based on the topology and normal directions. The second step determines the tool movement patterns and the sweeping directions for each flat patch. Based on the above two steps, optimal tool paths can be calculated. Experimental tests are carried out on automotive body parts and the results validate the proposed approach. Note to Practitioners-This paper was motivated by the problem of automatically planning tool paths for spray forming using Programmable Powdered Preforming Process (P4) technology. However, the proposed approach can be applied to other surface manufacturing applications such as spray painting, spray cleaning, rapid tooling, etc. Existing tool planning approaches are not able to handle complicated, multi-patch surfaces. This paper proposes a methodology to partition complicated surfaces into easy-to-handle patches and generate tool paths with optimized thickness uniformity and tool motion performance. We tested the approach using simulation on sample automotive body parts and proved its feasibility. However, this approach requires that the parts to be sprayed belong to the sheet-metal type so that the part geometry can be analyzed on a plane. In our future research, we will run physical tests on actual parts and investigate the deposition effects on the thickness uniformity.