Study on a piezoelectric micropump for the controlled drug delivery system

We present the design of a new controlled drug delivery system potential for in vitro injection of diabetics. The system incorporates some integrated circuit units and microelectromechanical system devices, such as micropump, microneedle array and microsensor. Its goal is to achieve safer and more effective drug delivery. Moreover, a valveless micropump excited by the piezoelectric actuator is designed for the drug delivery system, and a simple fabrication process is proposed. A dynamic model is developed for the valveless micropump based upon the mass conservation. To characterize the micropump, a complete electro-solid-fluid coupling model, including the diffuser/nozzle element and the piezoelectric actuator, is built using the ANSYS software. The simulation results show that the performance of micropump is in direct proportion to the stroke volume of the pump membrane and there is an optimal thickness of the piezoelectric membrane under the 500 V/mm electric field. Based on this simulation model, the effects of several important parameters such as excitation voltage, excitation frequency, pump membrane dimension, piezoelectric membrane dimension and mechanical properties on the characteristics of valveless micropump have been investigated.     

Transport of drug particles in micropumps through novel actuation

Micropumps with various types of actuations have been used in lab-on-a-chip devices. In order to control the delivery of drug particles both in space and time and avoid clogging, other types of actuation mechanisms may be needed. In this study, a valveless micropump with novel actuation is proposed to transport particles for biomedical and environmental applications. The transport of drug particles through the designed valveless micropump is carried out through computational fluid dynamics combined with discrete particle transport methods. After convergence studies, the effects of actuation frequency, particle size and the resident times on the particle transport are investigated. Interestingly, both the actuation frequency and particle size have a strong effect in terms of resident times and the spatial distribution of the transported particles through the designed micropump. Based on the results obtained, the relationship between actuation frequency, fluid flow, and particle transport through the designed micropump is presented. The computational analysis presented demonstrates that it is possible to optimize the proposed valveless micropump design for specific delivery of drug particles for separation and sorting applications.     

Fully coupled modeling and design of a piezoelectric actuation based valveless micropump for drug delivery application

The precise control over the drug delivery involved in several vital applications including healthcare is required for achieving a therapeutic effect. For such precise control/manipulation of the drugs, micropumps are used. These micropumps are basically of two types viz. check valve-based and valveless micropumps. The valveless micropumps are preferable due to the congestion-free operation of diffuser/nozzle valves. In this paper, design optimization of a valveless piezo-electric actuation based micropump is carried out using COMSOL Multiphysics 5.0 by coupling two Multiphysics interface modules namely fluid–structure interaction and piezoelectric physics modules. Using simulation studies, the influence of pump design parameters including diffuser angle, diffuser length, neck width, chamber depth, chamber diameter and diaphragm thickness on net flow rate is studied. An optimal set of design parameters for the proposed micropump is identified. Further, the influence of actuation frequency on the flow rate is analysed. It is found that the proposed micropump is capable to deliver a net flow rate of 20 µl/min and a maximum back pressure attainable is 200 Pa.

     

Integration of UML and VHDL-AMS for analogue system modelling

This paper details a new object-oriented methodology that permits a unified modelling language (UML) behavioural representation of analogue circuits at system level. The proposed method demonstrates a novel approach to the problem of behavioural representation of an analogue topology, by constructing a consistent set of rules for automated mapping of the UML model to a VHDL-AMS specification. The VHDL-AMS specification enables behavioural simulation of the UML model and the methodology is validated using an analogue subsystem level application.Correspondence and offprint request to: C. T. Carr, Intelligent Systems Engineering Laboratory, University of Ulster, Magee Campus, Northland Rd, Derry, Northern Ireland, BT48 7JL, UK.Received May 2002 Accepted in revised form September 2003 by C. Delgado Kloos     

MEMS-based micropumps in drug delivery and biomedical applications

This paper briefly overviews progress on the development of MEMS-based micropumps and their applications in drug delivery and other biomedical applications such as micrototal analysis systems (μTAS) or lab-on-a-chip and point of care testing systems (POCT). The focus of the review is to present key features of micropumps such as actuation methods, working principles, construction, fabrication methods, performance parameters and their medical applications. Micropumps have been categorized as mechanical or non-mechanical based on the method by which actuation energy is obtained to drive fluid flow. The survey attempts to provide a comprehensive reference for researchers working on design and development of MEMS-based micropumps and a source for those outside the field who wish to select the best available micropump for a specific drug delivery or biomedical application. Micropumps for transdermal insulin delivery, artificial sphincter prosthesis, antithrombogenic micropumps for blood transportation, micropump for injection of glucose for diabetes patients and administration of neurotransmitters to neurons and micropumps for chemical and biological sensing have been reported. Various performance parameters such as flow rate, pressure generated and size of the micropump have been compared to facilitate selection of appropriate micropump for a particular application. Electrowetting, electrochemical and ion conductive polymer film (ICPF) actuator micropumps appear to be the most promising ones which provide adequate flow rates at very low applied voltage. Electroosmotic micropumps consume high voltages but exhibit high pressures and are intended for applications where compactness in terms of small size is required along with high-pressure generation. Bimetallic and electrostatic micropumps are smaller in size but exhibit high self-pumping frequency and further research on their design could improve their performance. Micropumps based on piezoelectric actuation require relatively high-applied voltage but exhibit high flow rates and have grown to be the dominant type of micropumps in drug delivery systems and other biomedical applications. Although a lot of progress has been made in micropump research and performance of micropumps has been continuously increasing, there is still a need to incorporate various categories of micropumps in practical drug delivery and biomedical devices and this will continue to provide a substantial stimulus for micropump research and development in future.     

Design and simulation of a piezoelectric micropump for drug delivery systems

Microsystem Technologies - In this paper a piezoelectric micropump to be used in a drug delivery system is presented, for the specific application of providing synthetic lacrimal fluid to people...     

Equivalent electrical network for performance characterization of piezoelectric peristaltic micropump

Utilizing an electronic–hydraulic analogy, this study develops an equivalent electrical network of a piezoelectric peristaltic micropump which has not been modeled the whole system operation completely by computational fluid dynamics (CFD) or equivalent electrical network so far due to its excessive complicated structure. The validity of the proposed model is verified by comparing the simulation results obtained using the SPICE (simulation program with integrated circuit emphasis) software package for flow rate spectrum and its maximum state of a typical micropump with the experimental observations for two working fluids, namely DI water and blood. The simulation results predict a maximum flow rate frequency and flow rate of 280 Hz and 43.23 μL/min, respectively, for water, and 210 Hz and 24.12 μL/min for blood. The corresponding experimental results are found to be 300 Hz and 41.58 μL/min for water and 250 Hz and 23.75 μL/min for blood. The relatively poorer agreement between the two sets of results when using blood as the working fluid is thought to be the result of the non-Newtonian nature of blood, which induces a more complex, non-linear flow behavior within the micropump. Having validated the proposed model, the equivalent network is used to perform a systematic analysis of the correlation between the principal micropump design parameters and operating conditions and the micropump performance. The results confirm the validity of the equivalent electrical network model as the first microfluidic modeling tool for optimizing the design of peristaltic micropumps and for predicting their performance.     

基于Monte Carlo模型的微型PLGA给药系统建模及仿真

多腔体的微型可降解高分子聚合物PLGA药物缓释系统是一种新型植入式给药微器件,其载体结构是结合药物释放的要求和高分子聚合物生物降解特性进行设计并利用MEMS工艺制备.为了解微型给药系统实际释药的性能,需要对其进行建模和仿真研究.基于体溶蚀的Monte Carlo溶蚀模型,建立了具有多腔体的微型PLGA给药载体的释药模型,并对腔体结构为圆形的微型给药系统进行了释药过程仿真.仿真结果表明本文建立的微系统释药模型可以较为准确的描述微系统的释药过程,仿真模型对进一步开发微型PLGA给药系统有重要的参考价值.     

On challenges of model transformation from UML to Alloy

The Unified Modeling Language (UML) is the de facto language used in the industry for software specifications. Once an application has been specified, Model Driven Architecture (MDA) techniques can be applied to generate code from such specifications. Since implementing a system based on a faulty design requires additional cost and effort, it is important to analyse the UML models at earlier stages of the software development lifecycle. This paper focuses on utilizing MDA techniques to deal with the analysis of UML models and identify design faults within a specification. Specifically, we show how UML models can be automatically transformed into Alloy which, in turn, can be automatically analysed by the Alloy Analyzer. The proposed approach relies on MDA techniques to transform UML models to Alloy. This paper reports on the challenges of the model transformation from UML class diagrams and OCL to Alloy. Those issues are caused by fundamental differences in the design philosophy of UML and Alloy. To facilitate better the representation of Alloy concepts in the UML, the paper draws on the lessons learnt and presents a UML profile for Alloy.     

PDM system implementation based on UML

The paper deals with a Unified Modeling Language (UML)-based approach for implementing Product Data Management (PDM) system. Such kind of system enables the management of the entire product lifecycle and related information about its design, its manufacturing and its in-service.

The interest of using an UML-based approach for modeling, specifying and implementing PDM systems is detailed. Then an implementation method is proposed in order to clarify the instantiation of UML diagrams into database entities. Regarding a business case study based on the needs of a turboprop aircraft development project, the preliminary implementation of PDM system is presented. The used UML diagrams for the modeling and integration of product, process, and resource data is detailed in order to argue the interest of an object-oriented approach in such kind of PDM implementation.     

Structural and microfluidic analysis of hollow side-open polymeric microneedles for transdermal drug delivery applications

In this paper, we present a new design of hollow, out-of-plane polymeric microneedle with cylindrical side-open holes for transdermal drug delivery (TDD) applications. A detailed literature review of existing designs and analysis work on microneedles is first presented to provide a comprehensive reference for researchers working on design and development of micro-electromechanical system (MEMS)-based microneedles and a source for those outside the field who wish to select the best available microneedle design for a specific drug delivery or biomedical application. Then, the performance of the proposed new design of microneedles is numerically characterized in terms of microneedle strength and flow rate at applied inlet pressures. All the previous designs of hollow microneedles have side-open holes in the lumen section with no integrated reservoir on the same chip. We have proposed a new design with side-open holes in the conical section to ensure drug delivery on skin insertion. Furthermore, the present design has an integrated drug reservoir on the back side of the microneedles. Since MEMS-based, hollow, side-open polymeric microneedles with integrated reservoir is a new research area, there is a notable lack of applicable mathematical models to analytically predict structural and fluid flow under various boundary conditions. That is why, finite element (FE) and computational fluid dynamic (CFD) analysis using ANSYS rather than analytical systems has been used to facilitate design optimization before fabrication. The analysis has involved simulation of structural and CFD analysis on three-dimensional model of microneedle array. The effect of axial and transverse loading on the microneedle during skin insertion is investigated in the stress analysis. The analysis predicts that the resultant stresses due to applied bending and axial loads are in the safe range below the yield strength of the material for the proposed design of the microneedles. In CFD analysis, fluid flow rate and pressure drop in the microneedles at applied inlet pressures are numerically and theoretically investigated. The CFD analysis predicts uniform flow through the microneedle array for each microneedle. Theoretical and numerical results for the flow rate and pressure drop are in close agreement with each other, thereby validating the CFD analysis. For the proposed design of microneedles, feasible fabrication techniques such as micro-hot embossing and ultraviolet excimer laser methods are proposed. The results of the present theoretical study provide valuable benchmark and prediction data to fabricate optimized designs of the polymeric, hollow microneedles, which can be successfully integrated with other microfluidic devices for TDD applications.     

Fault diagnosis for high order systems based on model decomposition

Fault detection observer and fault estimation filter are the main tools for the model based fault diagnosis approach. The dimension of the observer gain normally depends on the system order and the system output dimension. The fault estimation filter traditionally has the same order as the monitored system. For high order systems, these methods have the potential problems such as parameter optimization and the real time implementation on-board for applications. In this paper, the system dynamical model is first decomposed into two subsystems. The first subsystem has a low order which is the same as the fault dimension. The other subsystem is not affected by the fault directly. With the new model structure, a fault detection approach is proposed where only the residual of the first subsystem is designed to be sensitive to the faults. The residual of the second subsystem is totally decoupled from the faults. Moreover, a lower order fault estimation filter (with the same dimension of the fault) design algorithm is investigated. In addition, the design of a static fault estimation matrix is presented for further improving the fault estimation precision. The effectiveness of the proposed method is demonstrated by a simulation example.     

A digital smart product service system and a case study of the mining industry: MSPSS

Mining equipment products and services no longer meet the needs of future development in the mining industry due to high safety and operational risk. The deep integration of the product-service system (PSS) and digitization is required in the mining industry to promote industry transformation and safe and efficient production without changing the traditional operation mode. This paper proposes a smart product-service system for the mining industry (MSPSS) consisting of a smart product subsystem, stakeholders, smart service subsystem, and smart decision-making subsystem. The analytic hierarchy process (AHP) and virtual reality (VR) are used for decision-making, product selection, operation, and maintenance. The smart product subsystem outputs reliable digital products using three stages: digital design, virtual simulation and planning, and virtual debugging. The smart service subsystem is driven by data and digital technology and provides fault diagnosis and online maintenance services for complex mining products. A case study indicates that all stakeholders can participate seamlessly in the design process. The smart product subsystem uses iterative optimization (more than 100 iterations) to obtain the design results interactively. The smart service subsystem provides digitalized services throughout the entire process. Thus, a stable, reliable, and comprehensive product and service solution is provided for complex mining conditions. The output is used to guide the design, debugging, and operation of physical equipment. The MSPSS has higher design quality and efficiency, a shorter design time, and lower design cost (key performance indicator (KPI)) than the traditional design method.     

基于RUP的UML建模方法研究

文章介绍了基于RUP应用UML进行系统分析、设计,建立系统模型的简洁方法。文中通过对一个研究生综合管理系统的建模过程,给出了该方法的应用细节,并对该方法进行了验证。实践表明,在基于RUP以体系结构为中心的建模方法指导下,应用UML语言丰富的可视化表达元素,可以清晰、快速地定义出面向对象的软件系统模型。     

Reasoning about UML/OCL class diagrams using constraint logic programming and formula

Model Driven Engineering promotes the use of models as the main artifacts in software and system development. Verification and validation of models are key activities to ensure the quality of the system under development. This paper presents a framework to reason about the satisfiability of class models described using the Unified Modeling Language (UML). The proposed framework allows us to identify possible design flaws as early as possible in the software development cycle. More specifically, we focus on UML Class Diagrams annotated with Object Constraint Language (OCL) invariants, which are considered to be the main artifacts in Object-Oriented analysis and design for representing the static structure of a system. We use the Constraint Logic programming (CLP) paradigm to reason about UML Class Diagrams modeling foundations. In particular, we use Formula as a model-finding and design space exploration tool. We also present an experimental Eclipse plug-in, which implements our UML model to Formula translation proposal following a Model Driven Architecture (MDA) approach. The proposed framework can be used to reason, validate, and verify UML Class Diagram software designs by checking correctness properties and generating model instances using the model exploration tool Formula.     

基于SABER平台的MEMS系统级模型研究

多端口组件网络方法是一种新的系统级统一建模方法,通过该方法形成的多端口三维组建库可以实现MEMS器件的快速设计与仿真.利用该方法,在SABER仿真平台上搭建了MEMS固态引信核心子系统的系统级行为模型,并进行了一系列的仿真分析,包括小信号频域仿真,时域仿真.以及灵敏度仿真,其结果接近于有限元分析结果.采用多端口组件网络方法进行MEMS器件的设计可以满足设计要求,保证精度,提高设计效率.     

基于UML实时系统的分析和设计

介绍了统一建模语言的最新版本UML2及应用UML2进行实时系统设计的作用及意义.探讨了UML2中用在实时系统设计中的概念.结合一个使用UML2为家庭安全系统设计的例子,着重分析了系统的静态结构和动态行为,通过类图、顺序图、状态图等UML图描述系统的方法从整体上对系统建模,说明实时系统分析与设计过程.使用UML分析和设计系统能够提高软件设计的效率和质量增强软件的维护性和复用性.     

A framework for an integrated unified modeling language

The unified modeling language (UML) is one of the most commonly used modeling languages in the software industry. It simplifies the complex process of design by providing a set of graphical notations, which helps express the objectoriented analysis and design of software projects. Although UML is applicable to different types of systems, domains, methods, and processes, it cannot express certain problem domain needs. Therefore, many extensions to UML have been proposed. In this paper, we propose a framework for integrating the UML extensions and then use the framework to propose an integrated unified modeling language-graphical (iUML-g) form. iUML-g integrates the existing UML extensions into one integrated form. This includes an integrated diagram for UML class, sequence, and use case diagrams. The proposed approach is evaluated using a case study. The proposed iUML-g is capable of modeling systems that use different domains.     

一类串联控制系统的优化设计:Backstepping方法

针对一类多输入非线性串联系统提出了基于Backstepping方法的次优控制的设计.首先,将串联控制系统分为几个子系统,然后为每个子系统分别设计辅助子系统及相应的辅助控制变量,进一步利用State_DependentAlgebraicRiccatiEquation(SDARE)技术为每个辅助子系统设计次优控制律.设计出的次优控制律使得原状态变量和辅助控制变量(即:辅助反馈变量)具有一定的渐近特性,因此,不但可在线获得次优控制律的解析解,而且保证了原闭环系统的全局渐近稳定性.最后通过一个两输入的二阶串联系统的数字仿真结果验证了该优化设计方法的有效性.     

力矩输入有界的柔性关节机器人轨迹跟踪控制

为解决柔性关节机器人在关节驱动力矩输出受限情况下的轨迹跟踪控制问题,提出一种基于奇异摄动理论的有界控制器.首先,利用奇异摄动理论将柔性关节机器人动力学模型解耦成快、慢两个子系统.然后,引入一类平滑饱和函数和径向基函数神经网络非线性逼近手段,依据反步策略设计了针对慢子系统的有界控制器.在快子系统的有界控制器设计中,通过关节弹性力矩跟踪误差的滤波处理加速系统的收敛.同时,在快、慢子系统控制器中均采用模糊逻辑实现控制参数的在线动态自调整.此外,结合李雅普诺夫稳定理论给出了严格的系统稳定性证明.最后,通过仿真对比实验验证了所提出控制方法的有效性和优越性.