Development of a Ceramic Micro Heat Exchanger – Design,Construction, and Testing

This article presents the development of a ceramic micro heat exchanger. Starting from its geometrical design, results obtained from a simplified simulation of the heat exchanger efficiency will be given. The alumina microcomponents were manufactured by a rapid prototyping process chain. Here, stereolithography was combined with a low‐pressure injection molding process for the rapid and precise manufacturing of ceramic components down to the micrometer range. A micro heat exchanger, joined from sintered components using a glass solder, was applied as a prototype and checked for its performance at a system pressure of 8 bar.     

Uncertainty contribution of tip-sample angle to AFM lateral measurements

AFM measurements are very important for quality control in the photovoltaic, microfluidic, electronic or micro-optic industries. This work proposes an algorithm to complete the uncertainty evaluation of AFM systems along the XY-axis under conditions where tolerance of curved surfaces must be controlled. This algorithm is also tested for tilt angles between tip and sample from 0° to 9° using an experimental arrangement which consists of an AFM instrumented with an inclinometer and four step height standards.Results show good agreement between the theoretical model and experimental results for samples with larger steps TGZ03 (465 nm) and TGZ11 (1416 nm), but with poor results for the smaller samples TGZ01 (17.6 nm) and TGZ02 (73.1 nm). An angle of 9° shows an error of about 3% in the horizontal determination of the step dimension, but it could increase to 47% for a tilt angle of 30° according to the theoretical model.The angle error between tip and sample is included in the uncertainty budget using a uniform distribution. An evaluation is performed in a theoretical rolling machine for imprint lithography where a step must be measured with nominal dimensions of 3 μm—X-axis and 1 μm—Z-axis. An assumed tip-sample angle is assumed that changes from 0° to 22.5° (curved form) and produces an uncertainty contribution to the X measurement of 55.7 nm. This uncertainty is important and must be considered to guarantee tolerances in quality control of curved form products.     

微技术的研究现状与发展趋势

阐述了微技术的研究内容，现状及发展趋势。     

Effect of Alternating Pumping of Two Reactants into a Microchannel on a Phase Transfer Reaction

Alternating pumping of two reactants into a microchannel was found to provide, in comparison with batch processes, a more effective mixing and an increased yield for a particular organic reaction which uses a phase transfer catalyst. The superiority of the microreactor method increased with the frequency of alternation of the pumping of the two liquids.     

Microclamping principles from the perspective of micrometrology – A review

This paper gives an overview of the field of clamping and gripping principles from the viewpoint of sample fixturing for dimensional metrology for microobjects. The requirements for clamping microcomponents that allow dimensional measurements are therefore explained before principles and solutions of microclamps as found in literature are reviewed and evaluated on basis of these requirements. Results show that there is no single superior clamping principle or method of implementation but rather several effective solutions for specific applications. The core value of this paper is the link between requirements for sample fixturing in dimensional micrometrology and the many approaches already investigated in the field of microclamping. A radar chart and a decision tree summarize and visualize the major aspects of this review. Finally, directions of future key research areas are suggested.     

微细台阶测量技术的发展现状

微细台阶参数是大规模集成电路和微机械结构制作过程的重要技术指标 ,直接影响器件和构件的特性 ,目前要求台阶测量应具有纳米级精度。概要介绍了台阶测量技术的发展情况 ,阐述了非接触台阶测量和接触式台阶测量技术 ,从测量原理、测量精度与分辨率、适用范围、对被测对象的要求与影响等几方面分析了各种测量方法的特点 ,并得出了结论。     

Multiscale lattice Boltzmann modeling of two-phase flow and retention times in micro-patterned fluidic devices

Recent advances for fabricating micro-featured architectures such as posts or pillars in fluidic devices provide exciting opportunities for multiphase flow management. Here we describe a novel, multiscale modeling approach for two-phase flows in microfeatured architectures developed within the Shan and Chen Lattice Boltzmann method. In our approach a fine scale is used to resolve the true microfeatured architecture, with a coarser scale used to model the gross geometry of the device. We develop the basic features of the approach and demonstrate its applicability to modeling retention times of droplets of a dispersed phase in an array of microposts – an architecture used in microfluidic reactors, bioreactors, and biomedical devises. Additionally we show that it is feasible to model the microfeatured geometry in a piecewise manner which includes extrapolating dispersed phase flow characteristics in the entire system based on simulations in smaller subdomains.     

Microscale pattern transfer without photolithography of substrates

In this paper, we have described a process to transfer microscale patterns on a fully exposed (unpatterned) substrate. The method uses electrochemical means and a specialised electrochemical reactor for pattern transfer. This process uses a metallic material with a resist pattern, which serves as an electrochemical tool. The substrate, which is fully exposed, is placed facing the tool, within close proximity. The tool and the substrate are electrically connected so that the tool is the cathode and the substrate is the anode. Electrolyte is pumped through the system to deliver fresh solution to the anode and cathode as well as remove reaction byproducts. Our initial experiments, involving copper as the tool as well as substrate material, showed that microscale patterns could be transferred with good reproducibility. In our reactor, they were placed within a distance of 500 μm. We have successfully transferred micropatterns which are significantly smaller than the electrode gap, namely 50, 100 and 200 μm.     

Capillary Filling Flows inside Patterned‐Surface Microchannels

Capillary flows inside microchannels with patterned‐surfaces are investigated theoretically and numerically. The surface energy method is used to derive an equivalent contact angle (ECA) model for small capillary number flows. The SIMPLE algorithm using a volume of fluid (VOF) method is adopted to investigate the flows in those microchannels. The flow characteristics such as the liquid front shapes and the evolution of the liquid lengths are obtained. The numerical results reveal that capillary flows in a patterned‐surface microchannel still follow the traditional capillary theories. The ECA model is confirmed by the numerical results. It indicates that the capillary flows inside the patterned‐surface microchannels can be estimated by means of the homogeneous‐surface microchannels with the equivalent contact angle. The ECA model provides a good criterion for the total wettability of a patterned‐surface microchannel, as well.