Cells adhered and cultured on microcantilevers

This paper shows a novel method to cultivate cells on a π-shape microcantilever inside a polydimethylsiloxane microfluidic system. Only one lithography step was needed to precisely align and pattern a poly(2-hydroxyethyl methacrylate) hydrogel microstructure, of size 200 × 200 μm, onto a silicon nitride microcantilever inside the PDMS microfluidic device. Gelatin was used as a sacrificial layer to resolve the issue of the microfluidic and hydrogel microstructure sticking together, successfully releasing the microcantilevers. BHK-21 cells were successfully laden and cultivated on the hydrogel microstructures of microcantilevers for 24 h. The optical system consisted of a He–Ne laser, a charge-coupled device camera, and a position-sensitive detector, which was used to measure the deflections of the microcantilevers due to the laden cells. The deflection increased continually during the cell-laden period. Meanwhile, the deflection increased with increasing cell concentration. By repeating the cell-laden and culture experiment three times, the magnitude and trend of deflection of microcantilevers were almost the same. It demonstrates that the microcantilever-based biochip has adequate stability and provides reliable measurement results for drug screening applications in the future.     

A Microcantilever-Based Picoliter Droplet Dispenser With Integrated Force Sensors and Electroassisted Deposition Means

This paper introduces a picoliter droplet dispenser relying on an array of silicon microcantilevers. The microcantilevers bear fluidic channels, and liquid transfer is achieved by a direct contact of the cantilever tip and the surface. A high degree of control over the location and geometry of the fabricated patterns is ensured by incorporating force sensors and electroassisted deposition means, i.e., electrowetting actuation and electrospotting, to the devices. The cantilever array, a PC-controlled stage, and an electronic circuit dedicated to the piezoresistance measurements form a closed-loop system that enables the automatic displacement of the array and the control of the deposition parameters. By using an external loading chip, different liquids are loaded onto the cantilevers, enabling the parallel deposition of several entities in a single spotting run. This paper details the design of the cantilevers assisted by finite-element modeling, the fabrication of the cantilever array, and the closed-loop operation. Moreover, proof-of-concept experiments are presented to demonstrate the versatility of our deposition system in terms of deposited materials and spot sizes. The control of the spotting process, the versatility of the printed materials, and the added electroassisted features prove that this tool has a real potential for research work and industrial applications.     

一种基于优化的自适应遗传算法的粒子滤波算法

针对粒子滤波的粒子退化现象及多样性损失问题,提出了一种新的基于优化的自适应遗传算法的粒子滤波算法。该算法首先依据每个采样时刻生成的粒子集合重要性权值作为适应度值,自适应的确定交叉、遗传的概率;然后对选出的粒子进行遗传操作,重新度量其粒子的权值并进行状态估计。该方法不仅保留了粒子的多样性,而且相对于普通的基于自适应遗传算法的粒子滤波算法,降低了高权值粒子交叉和变异的可能,使粒子的采样更接近于状态后验概率密度分布。实验结果表明,该算法有效提高了滤波精度。     

Interaction of the classical particle and quantum apparatus

The measurement process is considered through the interaction of the particles. The statistical operator of a single particle describes the classical behaviour while the interference term of the particles describes the quantum behaviour. A free single particle is treated classical. An apparatus consisting of two particles is treated quantum. The free particle is involved in the quantum superposition through the interaction with the apparatus. Collapse of the superposition state of the apparatus leads to the projection of the particle onto a definite state.     

Influence of pH on particle size and sensing response of chemically synthesized chromium oxide nanoparticles to alcohols

Nanoparticles of chromium oxide have been synthesized by following a co-precipitation route at various pH values of the precursor solution. Structural and morphological analysis were carried out by using XRD and TEM techniques which revealed that the size of nanoparticles synthesized at pH 9 was smaller as compared to those synthesized at other pH values. The thick films of synthesized samples were deposited on alumina substrate and their sensing response to methanol, ethanol and isopropanol was investigated at different operating temperatures. It was observed that all the sensors gave optimum response at 250 °C. It has been observed that sample prepared at pH 9, being a collection of smallest particles as compared to other samples, exhibited high sensing response to alcohol vapour. Sensor response of all the samples tested was significantly higher towards isopropanol vapour than towards methanol or ethanol.In the present study the effect of particle size on intergranular activation energy has been studied as well. It was found that smaller particles possess high activation energy and exhibit higher sensing response as compared to that of larger particles. This type of study may help in the selection of particle suitable for gas sensing.     

自适应不完全重采样粒子滤波器

针对传统重采样算法易引起粒子贫化的问题,提出了自适应不完全重采样粒子滤波 (A particle filter based on adaptive part resampling, APRPF)算法. APRPF以分步的方式仅对部分粒子进行重采样,以递推的方式计算表征 粒子退化程度的度量函数(Measurement of particle degeneracy, MPD),直到满足给定条件.重采样后的粒子由新生粒子 和未参与重采样的粒子组成,前者的存在有助于缓解退化问题,后者可使粒子集保 持一定多样性.实验结果表明,与标准粒子滤波(Sampling importance resampling, SIR)、辅助变量粒子滤波(Auxiliary particle filter, APF)、正则化粒子滤波(Regularized particle filter, RPF) 三种滤波器相比, APRPF的估计精度高;由于平均重采样次数少,计算量也小.     

新型粒子群优化算法

现有粒子群优化存在局部收敛、对可调参数敏感等缺点.基于此,本文提出一种新型粒子群优化算法.首先,通过分析社会个体对其环境的认知规律,简化粒子更新公式使粒子位置的更新仅与粒子自身速度及其邻域内最优粒子位置相关.其次,基于粒子速度划分提出一种优势粒子速度小概率变异、劣势速度随机赋值方法.最后,通过优化4个典型测试函数验证了本文所提方法在优化解的质量、算法收敛速度及鲁棒性等方面的优异性能.     

改进的流体模拟固体边界处理算法

流体模拟是计算机图形学的一个重要研究分支,流体的固体边界处理一直是流体 模拟的研究重点,光滑粒子流体动力学(SPH)方法中的镜像粒子法是处理固体边界的一个重要方 法。镜像粒子法通过靠近边界的流体粒子在边界外动态生成对应的镜像粒子来处理固体边界问 题,但随着边界复杂程度的提高,传统的镜像粒子法生成镜像粒子的复杂度也随之提高,模拟 效率随之降低。为此,文章对镜像粒子法进行改进,提出一种新的镜像粒子场量求值方法,有 效地降低了复杂边界情况下生成镜像粒子的复杂度,且使靠近边界的流体粒子场量更加均匀。 仿真实验结果表明,随着流体模拟粒子数的增加以及边界复杂程度的提高,该方法比传统镜像 粒子法效率高的优势也更加明显。     

Effects of the binder material on the mechanical properties of thick-film magnetostrictive materials

This paper presents research carried out at the University of Southampton into the development of a magnetostrictive thick-film material suitable for use with silicon micromachined devices. This form of magnetostrictive material has previously been deposited onto alumina substrates and this paper reports further work on migrating the technology onto silicon. The evaluation of two alternative glass frits for use as the binder within the thick film is reported. The correct choice of the binder material is important in a thick-film material because it is responsible for binding the active material within the thick film into a composite material and also adhering the film to the substrate. A series of tests have been applied to samples fabricated using various glass frits to assess their mechanical properties and suitability for the micro-actuator applications.     

Interferometric study of reliability of microcantilevers driven by AlN sandwiched between two metal layers

Micro-electro-mechanical systems are exposed to a variety of environmental stimuli, making a prediction of operational reliability difficult. Here, we investigate environmental effects on properties of piezoelectrically actuated microcantilevers, where aluminum nitride is used as actuation material. The environmental effects to be considered include thermal and humid cycling, as well as harsh electrical loading performed under normal conditions. Investigated properties are defined for the static and dynamic behavior of microcantilevers. A Twyman-Green interferometer, operating in both stroboscopic regime and time-average interferometry mode, is used as a metrology tool. The initial deflection and frequency changes of the first resonance mode of the microcantilevers are monitored during accelerated thermal aging tests, humidity tests, as well as harsh electrical loading and fatigue tests. Finally, the resonant fatigue tests accelerated by application of a high voltage are accomplished to evaluate a lifetime of microcantilevers. Monitoring the micromechanical behaviors of devices driven by aluminum nitride during the lifetime tests assists monitoring of their long-term stability. Finite Element Modeling is used to identify critical areas of stress concentration in the cantilever structure and to further explain various failure mechanisms.     

Towards particle system based stress visualization

A particle system, as understood in computer science, is a novel technique for modeling robots in their environment. Particle systems have traditionally been used for modeling complex dynamics of fluids and gases. In this paper, as the main contribution, we adapt our earlier work on particle systems, to compute a preliminary stress visualization for a bipedal robot walking on a soft sediment. The underlying problem of modeling rigid objects with particles is solved by introducing rack particles that enforce structural rigidness while maintaining deformability under stress. The presented approach opens many new possibilities, as it provides a computationally lightweight and unified, complementary framework for computing a stress of interacting, moving components with underspecified, non-trivial materialistic properties.     

Swallow swarm optimization algorithm: a new method to optimization

This paper presents an exposition of a new method of swarm intelligence–based algorithm for optimization. Modeling swallow swarm movement and their other behavior, this optimization method represents a new optimization method. There are three kinds of particles in this method: explorer particles, aimless particles, and leader particles. Each particle has a personal feature but all of them have a central colony of flying. Each particle exhibits an intelligent behavior and, perpetually, explores its surroundings with an adaptive radius. The situations of neighbor particles, local leader, and public leader are considered, and a move is made then. Swallow swarm optimization algorithm has proved high efficiency, such as fast move in flat areas (areas that there is no hope to find food and, derivation is equal to zero), not getting stuck in local extremum points, high convergence speed, and intelligent participation in the different groups of particles. SSO algorithm has been tested by 19 benchmark functions. It achieved good results in multimodal, rotated and shifted functions. Results of this method have been compared to standard PSO, FSO algorithm, and ten different kinds of PSO.     

基于卡尔曼粒子滤波器的人眼跟踪

提出了一种基于卡尔曼粒子滤波器的人眼跟踪算法，该方法利用一种新的二维可变形模板来提取眼睛的精确特征，采用粒子滤波器跟踪人眼。为了进一步提高普通粒子滤波器跟踪的速度和精度，将卡尔曼滤波器引入粒子滤波器中，利用卡尔曼滤波器算法进行采样预测和校正，减少了人眼跟踪中所需的粒子数目，从而达到快速而准确的跟踪目的。最后，用上述方法进行了实验，验证了该方法的实用性和有效性。     

A new method for the interaction between multiple DEP particles: iterative dipole moment method

Dielectrophoresis for bio-particle manipulation has been drawing much attention in recent years. The equivalent dipole moment has been widely used to calculate dielectrophoretic forces on a particle, but this method falls short to describe the interaction between neighboring particles. The Maxwell stress tensor method (MST) is theoretically rigorous for particle interaction, but it will cost huge computing resource. In this paper, an iterative dipole moment method (IDM) is presented to investigate the interaction between multiple dielectrophoretic particles in a two-dimensional electric field. Without any cumbersome numerical computation, the inter-particle forces and the particle trajectories calculated by the IDM method are found to be in good agreement with those by the MST method for some published results. Furthermore, it is found that the final stable particle chain patterns strongly depend on the initial configuration of the particle distribution. An arbitrary small disturbance to the particle locations may lead to dramatically different motion trajectories and final particle chains.     

微悬臂梁矩阵细胞牵引力测量传感器研制

提出一种采用聚碳酸酯核孔膜为模版来制作高深宽比聚二甲基硅氧烷微悬臂梁矩阵的新方法,用来作为生物微机电系统传感器探测细胞微纳力学及在体外研究细胞的机械特性,并对其制作工艺进行研究.通过选择不同的膜,可以便捷制作不同规格的微悬臂梁矩阵来满足不同精度的测量需求.细胞贴附在经表面处理后的微悬臂梁矩阵顶端生长并延展迁移,造成微悬臂梁弯曲形变.通过对形变共焦荧光显微图像处理,可以精确描绘出细胞牵引力分布.实验结果表明该制作方法有效,测量精度达到nN/μm.     

Studies of particle holding,separating, and focusing using convergent electrodes in microsorters

This paper presents numerical simulation results on the efficacy of dielectrophoretic (DEP) convergent electrodes in a particle sorter. DEP forces created by non-uniform electric fields are used as holding forces to trap and select the particles from a mixture of many samples, as well as confining forces to focus the particles into a single particle stream in the microsorter for further analysis. The key mechanism of the sorter that can hold particles against destabilizing fluid flows is investigated in this study. A barrier is found at X/L=0.84 and Y=0 in the present DEP sorter. By comparing the DEP and hydrodynamic forces at the barrier, one can determine the release velocity when the zero-net-force condition ceases to exist and the particles start to be released.     

基于粒子分解的SPH并行算法研究与应用

作为一种典型的拉格朗日型无网格数值方法,光滑粒子流体动力学(SPH)方法在模拟自由表面流问题时具有天然优势。但是,该方法计算量大、耗时长,为此提出了一种基于粒子分解的SPH并行算法。该算法将所有粒子平均分配到各个进程进行计算,每个时间步通信仅调用一次发送、接收和广播函数,因此易于实现且可扩展性较好。应用该并行算法对二维溃坝流和三维液滴冲击液膜问题进行数值模拟,结果表明：该并行算法能显著减少模拟所消耗的计算时间,有利于进行三维大规模计算问题的数值模拟;当粒子数大于百万时,最大加速比可达30以上。     

Analysis of Rank-Based Resampling Based on Particle Diversity in the Rao–Blackwellized Particle Filter for Simultaneous Localization and Mapping

In order to solve the simultaneous localization and mapping (SLAM) problem of mobile robots, the Rao–Blackwellized particle filter (RBPF) has been intensively employed. However, it suffers from particle depletion problem, i.e., the number of distinct particles becomes smaller during the SLAM process. As a result, the particles optimistically estimate the SLAM posterior, meaning that particles tend to underestimate their own uncertainty and the filter quickly becomes inconsistent. The main reason of loss of particle diversity is the resampling process of RBPF-SLAM. Standard resampling algorithms for RBPF-SLAM cannot preserve particle diversity due to the behavior of their removing and replicating particles. Thus, we propose rank-based resampling (RBR), which assigns selection probabilities to resample particles based on the rankings of particles. In addition, we provide an extensive analysis on the performance of RBR, including scheduling of resampling. Through the simulation results, we show that the estimation capability of RBPF-SLAM by RBR outperforms that by standard resampling algorithms. More importantly, RBR preserves particle diversity much longer, so it can prevent a certain particle from dominating the particle set and reduce the estimation errors. In addition, through consistency tests, it is shown that RBPF-SLAM by the standard resampling algorithms is optimistically inconsistent, but RBPF-SLAM by RBR is so pessimistically inconsistent that it gives a chance to reduce the estimation errors.     

Electro-optical characterization of IC compatible microcantilevers

The aim of this work is to simulate and optically characterize the piezoelectric performance of complementary metal oxide semiconductor (CMOS) compatible microcantilevers based on aluminium nitride (AlN) and manufactured at room temperature. This study should facilitate the integration of piezoelectric micro-electro-mechanical systems (MEMS) such as microcantilevers, in CMOS technology. Besides compatibility with standard integrated circuit manufacturing procedures, low temperature processing also translates into higher throughput and, as a consequence, lower manufacturing costs. Thus, the use of the piezoelectric properties of AlN manufactured by reactive sputtering at room temperature is an important step towards the integration of this type of devices within future CMOS technology standards. To assess the reliability of our fabrication process, we have manufactured arrays of free-standing microcantilever beams of variable dimension and studied their piezoelectric performance. The characterization of the first out-of-plane modes of AlN-actuated piezoelectric microcantilevers has been carried out using two optical techniques: laser Doppler vibrometry (LDV) and white light interferometry (WLI). In order to actuate the cantilevers, a periodic chirp signal in certain frequency ranges was applied between the device electrodes. The nature of the different vibration modes detected has been studied and compared with that obtained by a finite element model based simulation (COMSOL Multiphysics), showing flexural as well as torsional modes. The correspondence between theoretical and experimental data is reasonably good, probing the viability of this high throughput and CMOS compatible fabrication process. To complete the study, X-ray diffraction as well as d₃₃ piezoelectric coefficient measurements were also carried out.     

一种新的基于发散度函数的地形模型简化方法

提出了一种新的地形模型简化方法,该方法是在隐式四叉树层次结构基础上,结合离散粒子群思想建立地形的简化模型.文中重新定义粒子为具有层次信息的特征点的集合,从而每个粒子与简化模型的一个候选解相对应.为了实现多个粒子的空间压缩和快速检索,给出了隐式四叉树层次结构的快速索引方法.此外提出了基于法向矢量夹角的发散度函数的误差计算方法,重新定义了既满足地形模型误差要求同时兼顾模型简化比例的粒子评价函数,使地形简化模型在保持细节特征和轮廓特征的同时获得了更优的简化比率和模型精度.最后采用最优粒子作为启发信息引导简化过程,因此多个粒子迅速收敛于最优简化模型,从而模型的简化效率大大提高.文中方法均在多个基准数据上进行实验研究,结果表明与经典层次简化方法相比,算法效率和模型精度均显著提高.