Key Engineering Materials Vol. 613

Abstract: The micropump is the executive component in a microfluidic chip which impels the sample to flow. Its performance directly affects the precision and reliability of Micro Total Analysis Systems (μTAS), and it also plays a key role in the targeting transport of trace substances. The single and double chamber valveless micropumps with saw-tooth microchannel were designed. The saw-tooth diffuser/nozzle pipe was fabricated on chrome glass substrate using MEMS technology and the pump diaphragm was manufactured by PMMA material. The piezoelectric bimorph with cantilever beam was adopted as driving pump actuator and PDMS material as pump diaphragm. The valveless micropumps for both single and double chambers were formed with different saw-tooth structure parameters. The flow rate increased about 25% when the sidewall of microchannel changed from smooth to saw-tooth, and with the driving voltage increasing, the positive and negative flow difference of saw-tooth diffuser/nozzle pipe increased significantly, so does the micro pump flow rate. The best diffused angle θ was determined by the microchannel length L of saw-tooth diffuser/nozzle pipe, and the micro pump operated with its maximum flow rate only when the length-width ratio A reached the best value. The flow rate of a saw-tooth diffuser/nozzle valveless micropump with parallel double chambers increased approximately 30% than that of a single chamber.

Abstract: With an efficient system for 3D-mikrofocus-computed-tomography, the analysis of materials, welding’s, joining’s and structures, with high resolution is possible. In the research center Jülich such a tomographic system is available and has been developed continuously for a wide range of applications. The field of work of the X-ray system and the applications ranges from the analysis of organic materials up to solid metal components like welding’s and joining technologies. The image acquisition is carried out by novel flat panel detectors. The performance of the 3D visualization is demonstrated using examples from various scientific areas and applications. The system makes it feasible to extend automatic defective recognition (ADR) also on a real-time basis. By the special construction and the choice of its components, in combination with individually developed software tools, different application spectra are possible, e.g. for rapid prototyping or reverse engineering as well as FEM analysis in real components.

Abstract: The aim of this scientific work is to present different piezoresistive materials suitable to be integrated into micromechanical force sensors. As material for the mechanical structure of the sensors SU-8 has been chosen because it features favorable characteristics, such as flexible and simple fabrication of micro components through the use of standard UV lithography for forming three dimensional geometries such as cantilevers and membranes. In addition, on the basis of a significantly lower Young’s modulus compared to silicon, great opportunities to improve the force sensitivity of such sensors are offered by SU-8.However, SU-8 photoresist does not have piezoresistive properties, and therefore it has to be combined with an additional, beneficial piezoresistive material. A well-controlled and frequently used material for piezoresistive elements is doped silicon. This paper provides an overview of characteristics such as gauge factor and temperature coefficient of resistance (TCR) for a variety of commonly used piezoresistive materials, namely metals, silicon, conductive composite materials and diamond-like carbon. As a characteristic factor for the estimated sensitivity of the force sensor, the ratio of the gauge factor k to the Young´s modulus E of the structural material is presented for the different material combinations. A classification of conventional silicon based tactile force sensors is made to build a basis for comparison. Furthermore the suitability of different piezoresistive materials for the integration into an SU 8-based sensor is investigated.

Abstract: In this paper, substrate curvature method was adopted and a theory model based on Stoneys formula was built for obtaining the internal stress of SU-8 film. The effect of substrate diameter, film thickness and post-baked temperature on substrate curvature ratio was investigated by ANSYS simulation. The analytical result shows that post-baked temperature is the main effect factor on internal stress of SU-8 film. In addition, internal stresses of SU-8 at three different post-temperatures (55°C, 70°C and 85°C) are measured. The results show that the experimental results greatly agreed with simulation analytical results. It means the internal stress of SU-8 film can be accurately described by the theory model, which provides a basis for the quantitative analysis of the internal stress in SU-8 film.

Abstract: Polydimethylsiloxane (PDMS) has widely appeared in different electronic and medical applications. The knowledge of the thermal properties of PDMS and especially its thermal conductivity is required while processing PDMS to design a particular device. In this paper measurement of the thermal conductivity of PDMS using the three omega method is presented at different temperatures. The three omega method has been chosen because of its ease of use and accuracy. It requires the fabrication of metallic lines which act as heaters and thermometers on the surface of the material under test. A different procedure is introduced in this paper through which the metallic lines are embedded in the surface of PDMS. Experimental results are then compared to Cahill's approximate solution and to the results obtained by numerical simulations using a finite element method.

Abstract: To facilitate the calibration of a precision inertial navigation platform, the drifting of the platform under vibratory testing environment is analyzed, and a simplified drift model is developed which features the accumulative rather than instantaneous impact of the vibration on the platform drifting. When applied to error parameter calibration for the platform, the proposed model entails much less computing load in drifting prediction, and removes the requirement of strict real-time synchronization between the vibration generating device and the drift-predicting programs. The form of vibration can be assumed to be elliptic, a relatively general one which allows the shaker to vibrate sinuoidally in two directions perpendicular to each other and with phase difference of 90 degree. Under certain circumstances, the elliptic vibration can be simplified to a linear or circular one, as is typical in practice. Simulations of the platform drifting error under linear, circular and general elliptic vibration shows that the accumulative model can well serve as an alternative to the conventional one in such test environments, and the merits of the proposed model become more prominent when the frequency of vibration gets higher.

Abstract: The major challenge faced by a quality assurance (QA) system applied to small series production (SSP) is to guarantee the needed quality level already at the first run. Its called first time right on time. The SSP has some particular characteristics as the great diversity of product types and the continuous introduction of new products. Thus, the QA system has to adapt itself constantly to the new production conditions and support continuous process improvements. In this context, this paper presents the development of intelligent systems for QA in the diagnosis of SSP defects. The two systems developed are based on Artificial Intelligence techniques (Bayesian Networks, Expert Systems and Multiagent Systems) that analyze information from the metrological systems (such as a machine vision system) in the SSP line. The goal is to ensure that the cause of a defect will be fixed. The paper will present the context of the SSP, describe two solutions for quality assurance in SSP and will finish with the presentation of the results in the context of a SSP line for Printed Circuit Boards (PCB) mounting.

Abstract: At the so-called End-of-Line of the automotive final assembly the vehicles are commissioned, i. e. single systems as well as functions are checked and/or adjusted. For example, on the roll brake test stand, the parking brake and the driving brake are checked, whereas at the wheel alignment station the wheels are aligned. The commissioning processes are characterized by a high amount of manual work conducted by highly skilled workers with expensive equipment. Furthermore, many of the functions, which are commissioned at the End-of-Line (e. g. adjustment of the switching operation of the automatic transmission), have a high impact on the customers quality perception. Therefore, the improvement of the commissioning processes is a promising method to decrease costs in the automotive final assembly and increase the quality perceived by the customer. This paper presents an approach and in extracts its application that enables its users to improve commissioning processes at the End-of-Line of an automotive final assembly, regarding costs and quality perceived by the customer. The use-case employed in order to demonstrate the approach is the improvement of the steering wheel alignment.

Abstract: Probably one of the most significant developments in the field of software-defined multifunction data acquisition systems and devices is the employment of FPGA (Field-Programmable GateArray) technology, resulting in a tremendous digital processing potential close to the I/O pin. FPGA technology is based on reconfigurable semiconductor devices which can be employed as processing targets in heterogeneous computing architectures for a variety of data acquisition applications. They can primarily be characterized by generic properties, such as deterministic execution, inherent parallelism, fast processing speed and high availability, stability and reliability. Therefore FPGAs areparticularly suitable for use in “intelligent” data acquisition applications that require either in-line digital signal co-processing or real-time system emulation in the field of advanced control, protocol aware communication, hardware-in-the-loop (HIL) as well as RF and wireless test. From the perspective of a domain expert however, primarily being focused on developing applications and algorithms, simple and intuitive design entry methods and tools are required that facilitate the FPGA configuration and design entry process. Traditional FPGA design entry methods and commercially available tools assume a comprehensive knowledge of hardware description languages (HDL),such as VHDL or Verilog^®, and implement a process or function at register-level. In contrast, graphical hardware description languages for FPGAs, such as the integrated development environment NI LabVIEW^® with FPGA module extension, abstract the design process by means of graphical objects, I/O nodes and interconnecting wires that represent the FPGA’s IP and implement processes, timing, I/O integration and data flow. This paper discusses the advantages of graphical system design for FPGAs over text-based alternatives, introduces interfaces for the integration of 3^rd party IP, all backed up by a detailed illustration of a COTS FPGA-based multifunction DAQ target compared to a traditional DAQ architecture.

Abstract: Sensor devices with metrological self-check represent one of the most advanced directions in the present-day development of measurement technique. Generally, in the process of sensor device operation, results of the metrological self-check enable changes of metrological characteristics to be revealed, automatic correction of an error to be performed, grounds for multiple increase of a calibration interval to be obtained. In the present paper an additional procedure of metrological assurance is substantiated which provides the increase in the reliability of metrological self-check results.