Abstract Microvalves are important for fluid control in a variety of applications, ranging from miniaturized chemical analysis systems, to precision manufacturing and miniature fuel cells. MEMS technology provides the opportunity to miniaturize valves that work with smaller sample volume, operate rapidly with low power and can potentially be integrated with other components on a single chip. A review of actuators for microvalves is provided, including electrostatic, magnetic, piezoelectric, thermal, shape memory alloy and hydrogel. The design and simulation of a magnetic latching microvalve is provided as a case study. The fabrication by surface micromachining with low temperature, potentially CMOS compatible processing is given.

Abstract The development of microfabricated devices manufactured in silicon, glass, or plastic materials is a well‐known trend in the research of novel biological techniques and tools over the last two decades, resulting in a multitude of start‐up companies serving the pharmaceutical, biotechnology, and diagnostics markets. However, the idea of implementing such devices on microelectronic substrates has been introduced only recently. This chapter aims to describe the state‐of‐the‐art of microsystems for molecular and cell biology produced in general purpose CMOS (complementary metal oxide semiconductor) technology, emphasizing the advantages of this approach along with their challenges and limitations. This chapter discusses significant examples of fully tested devices in comparison with existing state‐of‐the‐art techniques.

Simultaneous, multi-site recording from the brain of freely behaving animals will allow neuroscientists to correlate neuronal activity with external stimulation and behavior. This information is critical for understanding the complex interactions of brain cells. Recent interest in microelectromechanical systems (MEMS) and in particular in bio-MEMS research has led to miniaturization of microelectrodes for extracellular neuronal recording. MEMS technology offers a unique opportunity to build compact, integrated sensors well suited for multi-site recording from freely behaving animals. These devices have the combined capabilities of silicon-integrated circuit processing and thin-film microelectrode sensing. MEMS probes for intracellular recording may offer significantly improved signal quality. Here we discuss the basic concepts that underlie the construction of intracellular MEMS probes. We first review the basics of neuronal signaling and recording, and the principles of microelectrode technology and techniques. Progress in MEMS technology for neuronal recording is then discussed. Finally, we describe MEMS probes for intracellular recording, viz., fabrication of micro-machined silicon needles capable of penetrating cell membranes. Using these needles, we recorded localized extracellular signals from the hawk moth Manduca sexta and obtained first recordings with silicon-based micro-probes from the inside of neurons, using an isolated brain of the sea slug Tritonia diomedea.

The cell patterning technique is important for observing living cells in a systematic way, especially from the viewpoint of nonlinear science, which enables us to treat a complicated system such as a living system by a form of mathematics. We developed a cell patterning method and constructed a living coupled oscillator system with the plasmodial slime mold, Physarum polycephalum, using a microfabricated structure. The plasmodium is a large ameboid unicellular organism consisting of an almost homogeneous structure without a highly differentiated system like a nervous system, but it shows a response to change in environment. The response behavior is considered to be caused by the interactions among the cell bodies where internal nonlinear oscillatory phenomena can be observed. Therefore, the plasmodium can be regarded as a coupled oscillator system. In order to understand the mechanism of the behavior of the plasmodium, it is essential to observe the behavior under conditions where the interactions among the cell bodies are systematically controlled. We patterned the shape of the plasmodium by a microstructure fabricated with a photoresist resin (SU-8) by a photolithographic method. With this system, we constructed two- and multiple oscillator systems of the plasmodium and observed oscillation phenomena by controlling the interaction parameters among the oscillators. We found that the oscillation patterns varied dynamically depending on the parameters in the same manner of the prediction by a mathematical model of a coupled oscillator system. This approach with side-by-side analyses is important for understanding complicated biological systems. In addition, for such analyses, the microfabrication technique is one of the key technologies.

In recent years, much effort has been expended to developing miniaturized, reliable sensors for measuring physical and chemical liquid properties. Microacoustic devices may be employed to determinate physical quantities perturbing the propagation conditions of the acoustic wave, even in liquid environments. For liquid sensors, acoustic modes with shear polarization are often used in order to avoid radiation losses. Examples are shear bulk modes, surface skimming bulk waves, shear-horizontal acoustic plate modes, and Love modes. Furthermore, modes with sagittal polarization may be applied if their phase velocity is sufficiently lower than the sound velocity in the adjacent liquid. General interactions between acoustic waves and liquids are viscous coupling, acoustoelectric effects, and mass loading. The resulting changes in device frequency and attenuation may be utilized for sensing purposes. The general advantages of microacoustic sensors are high sensitivity, simple fabrication, and quasidigital frequency readout. Hence, a wide variety of devices based on different modes for very different applications has been discussed in the relevant literature. The aim of this review is to provide a systematic overview of microacoustic sensors particularlay suited for operation in liquids. First, we provide a brief introduction to surface acoustic wave devices and the underlying physics, basic microacoustic structures, and general measurement techniques. A description of the mechanisms of interaction between liquids and acoustic waves is then followed by a comprehensive survey covering the different types of microacoustic liquid sensors, with emphasis on the mode-specific device properties. Thereafter, aspects of material selection and device fabrication are summarized. Lastly, an overview is given indicating where microacoustic liquid sensors have already been put into practice and where their application may be expected in the near future.

Research and development of automatic gas-sensor fire-detection systems are presented. An application in a mature state, the detection of smoldering fire in power plants, is described to some detail. First drafts of test procedures for gas-sensor fire-detection systems for general use and more specialized for aircrafts are sketched, these will guide the work on future systems. Signal evaluation discriminating a threatening fire from a non-threatening condition even at gas concentrations of only a few ppm is discussed. Gas sensors with potential for fire detection, especially with low-power consumption for building applications are described. Some of these sensors are just leaving the research labs. More selective sensors and arrays for detection at high background levels of those gases usually used for fire detection are pointed out. New functions of software for integration in industrial alarm control centers allow central parameter adaption to the surroundings of detector location.

Sensors UpdateVolume 7, Issue 1 p. 301-316 Sensor Applications - Time-domain Range New Time-domain Reflectometry Sensors for Water Content Determination in Porous Media M. Stacheder, M. Stacheder IMKO Micromodultechnik, Ettlingen, GermanySearch for more papers by this authorK. Koehler, K. Koehler IMKO Micromodultechnik, Ettlingen, GermanySearch for more papers by this authorR. Fundinger, R. Fundinger IMKO Micromodultechnik, Ettlingen, GermanySearch for more papers by this author M. Stacheder, M. Stacheder IMKO Micromodultechnik, Ettlingen, GermanySearch for more papers by this authorK. Koehler, K. Koehler IMKO Micromodultechnik, Ettlingen, GermanySearch for more papers by this authorR. Fundinger, R. Fundinger IMKO Micromodultechnik, Ettlingen, GermanySearch for more papers by this author First published: 11 April 2001 https://doi.org/10.1002/1616-8984(200001)7:1<301::AID-SEUP301>3.0.CO;2-XAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume7, Issue1January 2000Pages 301-316 RelatedInformation