This paper presents the modelling, design, fabrication and characterization of flow sensors based on the wind-receptor hairs of crickets. Cricket sensory hairs are highly sensitive to drag-forces exerted on the hair shaft. Artificial sensory hairs have been realized in SU-8 on suspended Si x N y membranes. The movement of the membranes is detected capacitively. Capacitance versus voltage, frequency dependence and directional sensitivity measurements have been successfully carried out on fabricated sensor arrays, showing the viability of the concept.

In this contribution three aspects of miniaturized total analysis systems (mTAS) are described and discussed in detail. First, an overview of microfabricated components for fluid handling is given. A description of the importance of sampling-and fluid-handling techniques is followed by details of microvalves, micropumps and micro flowchannels. Secondly, the problems associated with system integration are discussed. As a solution for the realization of microfluidic-and micro analysis systems, the concept of a planar mixed circuit board (MCB) as a platform for the integration of different components is described. In addition, the design, modeling and simulation, and realization of several components in the form of standard modules for integration on a MCB is described. As an illustration of the potential of this approach, the realization of a mTAS demonstrator for the optical detection of the pH change of a pH indicator, is presented. Finally, a number of different applications of mTAS are described, such as on-line process monitoring, environmental monitoring, biomedical and space applications and DNA-analysis.

This paper discusses the modeling, design and realization of micromachined Coriolis mass flow sensors. A lumped element model is used to analyze and predict the sensor performance. The model is used to design a sensor for a flow range of 0-1.2 g h −1 with a maximum pressure drop of 1 bar. The sensor was realized using semi-circular channels just beneath the surface of a silicon wafer. The channels have thin silicon nitride walls to minimize the channel mass with respect to the mass of the moving fluid. Special comb-shaped electrodes are integrated on the channels for capacitive readout of the extremely small Coriolis displacements. The comb-shaped electrode design eliminates the need for multiple metal layers and sacrificial layer etching methods. Furthermore, it prevents squeezed film damping due to a thin layer of air between the capacitor electrodes. As a result, the sensor operates at atmospheric pressure with a quality factor in the order of 40 and does not require vacuum packaging like other micro Coriolis flow sensors. Measurement results using water, ethanol, white gas and argon are presented, showing that the sensor measures true mass flow. The measurement error is currently in the order of 1% of the full scale of 1.2 g h −1 .

Arrays of MEMS fabricated flow sensors inspired by the acoustic flow-sensitive hairs found on the cerci of crickets, have been designed, fabricated and characterized. The hairs consist of up to 1 mm long SU-8 structures mounted on suspended membranes with normal translational and rotational degrees of freedom. Electrodes on the membrane and on the substrate form variable capacitors allowing for capacitive read-out. Capacitance versus voltage, frequency dependency and directional sensitivity measurements have been successfully carried out on fabricated sensor arrays, showing the viability of the concept. The sensors form a model-system allowing for investigations on sensory acoustics by their arrayed nature, their adaptivity via electrostatic interaction (frequency tuning and parametric amplification) and their susceptibility to noise (stochastic resonance)

A snnple to reahse micro-hqmd flow sensor wth hrgh senativlty 1s presented The sensor IS based on well known thermal anemometer pnnclples An analytIca model for the sensor behavlour apphcable for gas/hqmd fluids 1s presented The reahsatlon process of the sensor 1s described Model and expenmental results agree well The sensor 1s simple to Integrate Hrlth other micro-hqmd handling components such as pumps, mixers, etc 45

Ignition of exothermic chemical reactions in small volumes is considered as difficult or impossible due to the large surface-to-volume ratio. Here observation of the spontaneous reaction is reported between hydrogen and oxygen in bubbles whose diameter is smaller than a threshold value around 150 nm. The effect is attributed to high Laplace pressure and to fast dynamics in nanobubbles and is the first indication on combustion in the nanoscale. In this study the bubbles were produced by water electrolysis using successive generation of H(2) and O(2) above the same electrode with short voltage pulses in the microsecond range. The process was observed in a microsystem at current densities >1000 A/cm(2) and relative supersaturations >1000.

Two new methods have been developed to fabricate nanochannels by conventional micromachining. We succeeded in restricting the width of the channels to the submicrometer scale, while using standard photolithography with a resolution in the order of 1 µm. The first method is based on the sacrificial etching of a nanowire, which was formed on the side wall of a step. The second method is based on the adhesion of the capping layer to the substrate after removal of a sacrificial strip separating the two. The fabricated nanochannels are localized and can be connected to microchannels and reservoirs.

In this paper we describe components for integrated microliquid handling systems such as fluid injection analysis, and first results of planar integration of components. The components discussed are channels, passive and active valves, actuators for micropumps, micromixers, microflow sensors, optical detectors, pumps and dosage systems. The dosage system described comprises a flow sensor and a pump micromachined on a single silicon wafer sandwiched between Pyrex wafers. The liquid pump is of the reciprocating type with a thermo-pneumatic actuator. The microliquid flow sensor is based on the thermal anemometer type. Both pump and flow sensor are realized in a 3 inch (100)-Si wafer using a KOH bulk etch from both sides of the wafer. The dosing system allows accurate dosing of liquid in the wl regime and can easily be integrated with components as mixers and detectors to microliquid handling systems. A new concept for micromixing of liquids is introduced and its feasibility is demonstrated. The mixer allows fast mixing of small amounts of two liquids and it is applicable to microliquid handling systems. The,mixer has a channel for the liquid, an inlet port for t h e reagent, and a mixing area, the bottom of which has 400 micronozzles (15 p m x i 5 Nm). Through these nozzles, a reagent is injected into the sample liquid, making many microplumes. These plumes speed up mixing by diffusion over a short distance.