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Wideband 100 kHz–4 GHz power sensors are presented, which are based on sensing the electrostatic force between an RF signal line and a suspended membrane. The electrostatic force, which is proportional to the square of the rms signal voltage and thus to the signal power, results in a displacement of the suspended membrane. This displacement is detected capacitively, allowing the sensing of the signal power with extremely low dissipative losses; therefore the sensor can be placed in a transmission line with negligible disturbance of the signal. Devices have been designed and fabricated successfully by aluminum surface micromachining using photoresist as the sacrificial layer. Optimization of the design with SONNET has resulted in measured return and insertion losses (S11 and S21) better than −30 dB and −0.15 dB, respectively, up to 4 GHz, and a sensitivity of 90 aF mW–1.

In this paper the theory of water electrolysis in a closed electrochemical cell, that contains two electrodes, an electrolyte and a pressure sensor is described. From the leakage and electrochemical experiments done with this macrocell it is possible to obtain information about the applicability of the electrochemical principle in a closed cavity, the choice of the electrodes and electrolyte, and different types of leakage. To control the pressure of the electrochemical actuator automatically, an electronic feedback system was connected to the cell. A value of the pressure is set and the regulator will actuate the electrochemical cell in such a way to get the desired pressure.

The shuffle motor is a linear electrostatic stepper motor employing a mechanical transformation to obtain large forces and small steps. A model has been made to calculate the step size and the driving voltage as a function of the load force and the motor geometry. The motor consists of three polysilicon layers and has been fabricated using surface micromachining. Tests show an effective step size of about 85 nm and a produced force of 43 μN at 40 V driving voltage.

A surface micromachining process is presented which has been used to fabricate electrostatic microactuators. These microactuators are interconnected with each other and linked to other movable microstructures by integrated gear linkages. The gear linkages consist of rotational and linear gear structures, and the electrostatic microactuators include curved electrode actuators, comb-drive actuators, and axial-gap wobble motors. The micromechanical structures are constructed from polysilicon. Silicon dioxide was used as a sacrificial layer, and silicon nitride was used for electrical insulation. A cyclohexane freeze drying technique was used to prevent problems with stiction. The actuators, loaded with various mechanisms, were successfully driven by electrostatic actuation. The work is a first step toward mechanical power transmission in micromechanical systems.

Due to the smoothness of the surfaces in surface micromachining, large adhesion forces between fabricated structures and the substrate are encountered. Four major adhesion mechanisms have been analysed: capillary forces, hydrogen bridging, electrostatic forces and van der Waals forces. Once contact is made adhesion forces can be stronger than the restoring elastic forces and even short, thick beams will continue to stick to the substrate. Contact, resulting from drying liquid after release etching, has been successfully reduced. In order to make a fail-safe device stiction during its operational life-time should be anticipated. Electrostatic forces and acceleration forces caused by shocks encountered by the device can be large enough to bring structures into contact with the substrate. In order to avoid in-use stiction adhesion forces should therefore be minimized. This is possible by coating the device with weakly adhesive materials, by using bumps and side-wall spacers and by increasing the surface roughness at the interface. Capillary condensation should also be taken into account as this can lead to large increases in the contact area of roughened surfaces.

Reactive ion etching of silicon in an RF parallel plate system, using SF6/O2/CHF3, plasmas has been studied. Etching behavior was found to be a function of loading, the cathode material, and the mask material. Good results with respect to reproducibility and uniformity have been obtained by using silicon as the cathode material and silicon dioxide as the masking material for mask designs where most of the surface is etched. Etch rate, selectivity, anisotropy, and self-bias voltage have been examined as a function of SF6 flow, O2 flow, CHF3 flow, pressure, and the RF power, using response surface methodology, in order to optimize anisotropic etching conditions. The effects of the variables on the measured responses are discussed. The anisotropic etch mechanism is based on ion-enhanced inhibitor etching. SF6 provides the reactive neutral etching species, O2 supplies the inhibitor film forming species, and SF6 and CHF3 generate ion species that suppress the formation of the inhibitor film at horizontal surfaces. Anisotropic etching of high aspect ratio structures with smooth etch surfaces has been achieved. The technique is applied to the fabrication of three-dimensional micromechanical structures.

A micromechanically fabricated thermal flow sensor is presented. The sensor incorporates multiple, 100 μm spaced, resistive sensing elements on a glass substrate in a silicon flow channel. This sensor works on the principle of a travelling heat pulse through the fluid. The response to this heat pulse at different positions upstream and downstream from a heater is used to determine not only flow velocities but also fluid properties. Theoretical analysis of the sensor response shows that the sensor is more able to discriminate between flow velocities and fluid properties when certain combinations of sensing element signals are used. It is shown that the sensor can also measure mass flow as long as the 'time of flight' of a heat pulse can be measured at equal distances from the heater upstream and downstream. Combination of the 'time of flight' at two different positions downstream can be used to determine the diffusivity of the fluid. The sensor can be made sensitive to flow velocity by taking the heat pulse response at two different locations downstream at an instant in time when the signal amplitudes are equal. The 'time of flight' measured at one position downstream is only accurate when the velocities are high enough since the diffusive effect can be neglected. The ability of an artificial neural network to learn to discriminate between the flow velocity and fluid properties is analyzed.

Observation of a spontaneous reaction between hydrogen and oxygen in bubbles in water whose diameter is smaller than a threshold value around 150 nm is presented. The effect is attributed to high Laplace pressure and to fast dynamics in nanobubbles and is the first indication on combustion in the nanoscale. The bubbles were produced by water electrolysis in specially designed microchips using successive generation of H2 and O2 above the same electrode with short voltage pulses in the microsecond range. Diferent signatures indicating the combustion process are described.

Throughout the ages humanity has stored data in order to preserve important information for generations to come. As the years have progressed the amount of data that can be stored efficiently has increased tremendously, the lifespan of this type of data storage however is severely limited. Within this paper we investigate the possibility to store data by encapsulating W in a SiN matrix.We show that using accelerated thermal aging the possible lifespan of this medium can be investigated and expected to reach well into the millions of years, preserving data for thousands of future generations. The first steps into fabrication of such a medium are discussed.

“The Human Document Project‿ is a project which tries to answer all of the questions related to preserving information about the human race for tens of generations of humans to come or maybe even for a future intelligence which can emerge in the coming thousands of years. This document mainly focusses on how to store the data than other questions as what to store, where to store it and how to ensure readback is possible at all.

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 mu l 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 the reagent, and a mixing area, the bottom of which has 400 micronozzles (15 mu m*15 mu m). 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.

Counterfactual thinking plays a key role in research in physics and, I believe, in research in all natural sciences. In this contribution I will describe a few examples of counterfactual thinking, how it is used, the power of this method of inquiry, and the types of results that can be achieved. A brief account of the way physicists carry out research will be given and three main types of questions will be identified. Two of them will be used to illustrate the value of counterfactual thinking, one example regarding astronomy, and the other example dealing with electromagnetic forces. The latter might be quite tough for non-physicists. The last, most extended, part of this paper gives an analysis of counterfactual situations: what would the world look like if the constants of nature had different values. This discussion leads to the conclusion that slight changes of these numbers leads to uninhabitable worlds.

We present for the first time the combined measured piezoelectric and mechanical properties of epitaxial, (110) oriented Pb(ZrxTi1-x) (PZT) thin films grown on microfabricated silicon cantilevers using pulsed laser deposition (PLD, x=0.4, 0.52, 0.6 and 0.8). The grown PZT thin films develop a strong (110) preferred orientation, which results in an effective piezoelectric coefficient (d33,f) of 123 pm/V at the morphotropic phase boundary (Zr/Ti = 52/48). This value is 70% higher compared to sol-gel deposited films with an equal Young’s modulus [1]. The Young’s modulus of the PZT thin films was determined by measuring the shift in resonancefrequency of microfabricated cantilevers (shown in Fig. 1) both before and after deposition of the films by means of a scanning laser-Doppler vibrometer. To this end, we developed a model to calculate the Young’s modulus from the resonance frequency shift which includes an essential correction for the undesired undercut that is unavoidably introduced during the release of cantilevers [2]. The obtained Young’s modulus is independent on cantilever length, as expected. For a 100 nm thick PZT film with a Zr/Ti ratio of 60/40, the mean value of the measured Young’s modulus was found to be 122 GPa with a standard error of ± 1.3 GPa. Fig.2 shows an increase of the Young’s modulus of the PZT thin films with increasing Zr/(Zr+Ti) ratio. The PLD-PZT thin film presented in this work combines excellent piezoelectric properties with a high Young’s modulus, and is therefore a promising and exciting candidate for the active device layer in actuators and highly sensitive MEMS sensors.

We present an optical technique to detect cantilever deflection of an array using Fraunhofer diffraction patterns. Application areas include probe-based data storage. Intensity profiles of different cantilever arrays are captured on a CCD camera and compared with our model. These measurements are in excellent agreement with the Fraunhofer theory, less than 3% deviation is found. Each cantilever can either be deflected by a fixed amount or undeflected. Based on noise measurements on our setup and intensity patterns simulations, we predict that this method allows the measurement of 1nm deflections in an array of six cantilevers with an SNR of 35dB.

In this contribution we present the compositional dependence of the longitudinal piezoelectric coefficient (d33,f), residual stress and Young's modulus of Pb(Zrx,Ti1-x)O3 (PZT) thin films. Pulsed laser deposition (PLD) was used to deposit epitaxial PZT thin films with a < 110 > preferred orientation on silicon cantilevers. By using PLD, excellent piezoelectric properties of the PZT were observed which makes it an exciting piezoelectric material for the development of actuators and highly sensitive sensors. Our investigation of the compositional distribution of the piezoelectric coefficient (d33,f) for 250 nm thick films shows a maximum value of 93 pm/V for x=0.52. The static deflection of the cantilevers, measured after the deposition of PZT thin films was used to determine the residual stress for various compositions. The observed trend in the residual stress of PZT thin films is attributed to the varying coefficient of thermal expansion for different compositions. The Young's modulus of the PZT thin films was determined by measuring the flexural resonance frequency of the cantilevers both before and after the deposition. The Young's modulus increases for the zirconium rich PZT compositions, which is in agreement with the trend observed in their bulk ceramic counterparts.

This paper elaborates on the incorporation of in-plane electrical interconnects to the reflow bonding. After joining the tubes to silicon substrates, the electrically conductive lines will allow probing into the volume confined by the tube. Therefore methods of fabrication of electrical interconnects, which would survive the bonding and not alter the quality of the bond interface, are investigated.

Self-assembled DNA nanostructures promise low-cost ways to create nanoscale shapes. DNA nanostructures can also be used to position particles with nanometer precision. Yet, reliable and low-cost ways of integrating the structures with MEMS technology still have to be developed and innovations are of great interest to the field. We have examined in detail the adherence of DNA origami tiles on silicon oxide surfaces of wafers in dependence on pH-value and magnesium ion concentration. The results of this work will help to pursue new strategies of positioning DNA nanostruc-tures on SiO2. Precise control over the strength of structure-surface adhesion is a prerequisite of relia-ble processes.

In this work we show for the first time that the effective in-plane Young’s modulus of PbZr0.52Ti0.48O3 (PZT) thin films, deposited by pulsed laser deposition (PLD) on dedicated single crystal silicon cantilevers, is independent of the in-plane orientation of cantilevers.

We report on progress in the fabrication of cantilever arrays with tips. The process features only one lithographic step for the definition of both the tips and cantilevers. The tips have a uniform height distribution and are placed by selfalignment on the cantilever. The arrays are fabricated for an optical readout technique under development in which the cantilever arrays serve as diffraction gratings. This work describes our ongoing effort in array fabrication as well as preliminary results on optical readout of a previously fabricated batch of tipless cantilever arrays using Fraunhofer diffraction.

Borofloat® (borosilicate 8330) glass is an important type of inorganic glass, both scientifically and commercially. During prolonged heat treatment of this glass above its glass transition temperature of 525°C, heterogeneous nucleation, and growth of cristobalite crystals occur. The kinetics and morphology of this crystal growth have been studied for heat treatment temperatures at and above 660°C. The activation energy for crystal growth is estimated to be 185±10 kJ/mol. This is attributed to the diffusion of boron, rather than sodium, being the rate-limiting step within the borosilicate framework. Contact with the atmosphere is shown to initiate the nucleation of cristobalite crystals, while deposition of a thin silicon nitride surface coating on the glass helps to prevent this nucleation.

Calculation of the resonance frequency of cantilevers fabricated from an elastically anisotropic material requires the use of an effective Young’s modulus. In this paper a technique to determine the appropriate effective Young’s modulus for arbitrary cantilever geometries is introduced. This technique is validated using a combined analytical and finite element simulations (FEM) approach. In addition, the effective Young’s modulus of PbZr0.52Ti0.48O3 (PZT) thin films deposited on dedicated micromachined cantilevers was investigated experimentally. The PZT films were deposited on the cantilevers by pulsed laser deposition (PLD). The change in flexural resonance frequency of the cantilevers was measured both before and after deposition of the PZT thin film. From this frequency difference we determined the Young’s modulus of PZT deposited by PLD to be 103 ± 2 GPa. Even though the PZT is grown epitaxially, this value is independent of the in-plane orientation.

Integrated optical switches using mechano-optical sensing are gaining more attention in many fields due to their fast switching speed, large bandwidth and compact devices. In this paper, a micromachined electrostatically actuated metal plate to sense the evanescent field above the waveguide is presented. The feasibility of MEMS based light weight mechanical plates to achieve fast switching is evaluated. With decreasing distance between the suspended plate and the substrate it gets more difficult to control the gap due to forces resulting from parasitic charging and the Casimir effect. Measurement of the Casimir force between parallel plates at sub-micron distance is also cumbersome. A methodology to measure the Casimir force between parallel plates is presented here. The prime objective of this research is to come up with an ultra fast optical switch using parallel plates and also to measure the Casimir force between them.

In this work we present parallel optical readout of a cantilever array which operates in dynamic mode using a standard optical beam deflection configuration containing only one laser-detector pair. We show accurate readout of the resonance frequency shift of an individual cantilever within an array by designing arrays where each cantilever has a different resonance frequency. The different resonance frequencies are created by giving each cantilever a different length and allow parallel readout of all cantilevers within the array. We show that even if the cantilevers are closely spaced each cantilever resonance frequency can be individually tracked without signs of cross-talk at current measurement precision (below 12 mHz). Interference of the laser light reflecting of each cantilever is observed when the amplitude of the cantilever is on the order of the wavelength of the laser light.

The miniaturization of space applicable devices by means of micro system technology (MST) is pursued by many research groups. MST devices are often designed as stand alone and require individual packaging which makes them still quite large. Focusing on the integration of several MST components has the advantage of reducing size and mass much more. An integrated and miniaturized feeding and thruster system for micro satellites is presented which consists of a valve, a particle filter, a pressure sensor and a nozzle. The first prototype valve has been fabricated and tested.

To enable formation flying of micro satellites, small sized propulsion systems are required. Our research focuses on the miniaturization of a feeding and thruster system by means of micro system technology (MST). Three fabrication methods have been investigated to make a conical converging-diverging nozzle. These methods are reactive ion etching, femtosecond laser machining (FLM) and a combination of powderblasting and heat treatment. It is shown that the latter two methods are very promising.

The present invention provides an optical device, comprising an optical fiber and a cantilever that is arranged on an end of the optical fiber; The cantilever may be an integral part of the optical fiber, and may have a length that is substantially equal to a diameter of the optical fiber. Measurement means for measuring a displacement of the cantilever are connected to an opposite end of the, optical fiber. A method of measuring a displacement using the optical device comprises the steps of: —arranging measurement means, comprising a light source, on an opposite end of the optical fiber; —using the light source to send a beam of light into the optical fiber; —measuring the interference of light that is reflected on the end op the optical fiber and light that is reflected on the cantilever; and determining the displacement of the cantilever relative to an intermediate position dependent on the measured interference.

Capillary bonding of glass tubes to silicon wafers has been elaborated. After proper preparation, tubes are placed on silicon substrates and specimens are annealed at sintering temperatures of glass. The resulting interconnect is capable of working above 70 bars of filling pressure and the bond is completely hermetic. However, due to high temperature annealing in air, surface devitrification has been observed on glass, which can be avoided by vacuum annealing

The invention relates to a method for making a glass supported micro or nano system, comprising the steps of: i) providing a glass support; ii) mounting at least one system on at least one glass support; and iii) bonding the system to the glass support, such that the system is circumferentially supported within the confinement of the glass support, to a glass supported system, and to the use of a glass support therefor.

We present a novel ultrasensitive magnetometry technique using a micromachined magnetic cantilever that is brought in resonance. The induced magnetic moment generates a torque on the cantilever, thereby effectively stiffening the cantilever spring constant and changing its resonance frequency. Experiments are in good correspondence with the presented analytical model for this frequency shift, predicting the detection of nanotesla magnetic fields.

The sensitivity of an innovative acoustic sensor composed of four hot-wires is analyzed. An analytical model is presented that describes both the air flow and the temperature distribution in and around the probe. The presence of the chip surface in the vicinity of the wires influences the acoustic flow, while it also affects the temperature distribution. Both effects result into a specific angular dependence of the sensor sensitivity. Acoustic measurements are compared with theory, showing good correspondence.

We present a normally open stepper motor actuated microvalve based on micro and fine-machining technique. In this paper, first we have described how the larger controllable flow range can be achieved with simple micromachining techniques and secondly we have presented the results which show how the performance of the microvalve can be improved by using combination of different metal screws for mechanical transmission of power to deflect the membrane to control the flow of gas.

1D nanochannels are fabricated by direct bonding between the silicon wafer containing the nanochannels, microchannels, access holes and the blank thin glass of 170 µm thickness. The thin glass wafers are used as channel covers because of their appropriate thickness for use with coverglass corrected water immersion lenses. As the nanochannel chips are used on an inverted microscope, access holes are created in the silicon wafer so that polyimide is good selection for protection during deep etching of the macro holes. Fabricated nanochannels with 50 nm depth were successfully filled with low concentration of solutions Alexa 488 could be observed through fluorescence microscopy. These nanochannels are promising for mobility studies of single molecules such as quantum dots.

The omni-directional sensitivity pattern of an integrated three dimensional acoustic sensor, composed of four hot-wire particle velocity sensors is analyzed theoretically and experimentally. We investigate the influence of the presence of the probe surface on the direction of the measured particle velocity measured by the sensors, and a description of the gas flow profile around the integrated sensor is presented.

This article presents microchannel thermal flow sensors fabricated using standard micromachining technology. The sensors comprise of a SiXNY microchannel created by etching of a poly-Si sacrificial layer. The channels are released by KOH etching through inlets and outlets etched from the backside of the substrate. Liquid flow is measured by platinum resistors deposited on top of the microchannel, while the channel is thermally isolated from the substrate by a SiXNY membrane. Flow rates of DI water in the order of nl⋅min-1 have been measured using a dynamic sensing method applying heat waves.

This work investigates the fundamental growth of c-axis oriented piezoelectric AlN thin films by RF reactive sputtering on p-type (100) and (110) silicon substrates. Substrates are treated with a 1% HF solution before deposition to remove the native oxide followed by backsputtering using argon ions. X-ray diffraction shows a (0001) oriented columnar texture of AlN grains which is the preferred orientation for piezoelectric applications. TEM shows the presence of a 4 nm thick semi-crystalline interface between silicon and the AlN layer. A basic growth mechanism is proposed from microstructural observations.

Thick silicon nitride blocks embedded in silicon wafers were recently proposed as a substrate for RF devices. In this paper we show that deep trenches filled with silicon nitride—having thin slices of monocrystalline silicon in between—already result in a significantly improved RF behavior. Measurement results are presented on RF coplanar waveguides using solid silicon nitride blocks and silicon nitride filled trenches with various dimensions and orientations with respect to the transmission line. A clear difference exists between trenches parallel and perpendicular to the transmission line due to the different associated loss mechanisms. S-parameter measurements on the coplanar waveguides show an improvement of the transmission losses at 4 GHz from 3.5 dB mm-1 on a standard silicon substrate to 0.7 dB mm-1 on silicon nitride filled trenches and 0.2 dB mm-1 on a solid silicon nitride block. In this way, an RF performance very close to dedicated glass substrates such as AF45 is obtained (with transmission losses of 0.1 dB mm-1 at 4 GHz).

Keywords: Nanochannels, capillarity, viscosity

The packaging effects of an acoustic particle velocity sensor have been analysed both analytically and by means of finite volume simulations on fluid dynamics. The results are compared with acoustic experiments that show a large magnification of the output signal of the sensor due to the mounting inside a cylindrically shaped package. The influences of the package consist of a decrease of the output signal at frequencies below 1 Hz, whereas signals with frequencies above 10 Hz are amplified by a constant factor of approximately 3.5 (11 dB). The analysis leads to an improved insight into the effects of viscosity and fluid flow that play a role in flow sensing and opens the way for further optimisation of sensitivity and bandwidth of the sensor.

This article presents an analysis for two related concepts of a capacitive incremental position sensor. In Incremental Capacitance Measurement Mode the periodic change in capacitance is measured to determine the relative displacement between two periodic geometries S1 and S2 with gap-distance of ~ 1 μm. In Constant Capacitance Measurement Mode the distance between S1 and S2 is controlled to keep the capacitance between S1 and S2 constant. Analysis and 2D- Finite Element simulations show that SNR for CCMM can be >300x over ICMM and with a lower non-linearity in the position sensor signal, CCMM will perform better in accurate quadrature position detection.

Nickel thin films have been electrodeposited directly on highly doped silicon wafers after removal of the native oxide layer. These substrates conduct sufficiently well to allow deposition using a periferical electrical contact on the wafer. Films 2 μm thick were deposited using a nickel sulfamate bath on both n+ and p+-type silicon wafers, where a series of trenches with different widths had been previously etched by plasma etching. A new, reliable and simple procedure based on the removal of the native oxide layer is presented which allows uniform plating of patterned substrates.

We present a surface micromachining process to fabricate AlN piezoelectric microstructures. The fabrication process utilizes Si02 sacrificial layer etching with Polysilicon as a structural layer. The significance of the process is that the polysilicon layer is used as a structural as weIl as a bottom electrode layer. A thin layer of Cr is used as a mask layer to etch both the AIN and polysilicon layers, while acting as a top electrode. The fabricated clamped-clamped beam microbridges show compressive stress. Preliminary results using phase-shift interferometry measurements show displacements of 8.3nmN on a typical microbridge with dimensions 385 x 50 /-lm.

The anisotropic etch rate of p-type single crystal silicon has been systematically studied as a function of an externally applied electrical potential. Changes in overall etch rate are consistent with a combined chemical etching and electrochemical oxidation mechanism. Etch rate results of orientations close to (111) indicate that, at these surfaces, etching follows a step mechanism. Additionally it shows a difference in reactivity between monohydride and dihydride terminated steps towards both chemical etching and electrochemical oxidation. Morphology changes have also been observed, in particular on (110) surface, where the macroscopic surface becomes smoother at positive bias.

At the University of Twente, research on the development of a sorption-based micro cooler is in progress. Because of the absence of moving parts, such a cooler is virtually vibration free and highly durable, which potentially results in a long lifetime. A miniature cryogenic cooler with these properties would be appealing in a wide variety of applications including the cooling of vibration-sensitive detectors in space missions, low-noise amplifiers and semi- and superconducting circuitry. The objective of the present project is to scale down a Joule-Thomson (JT) cold stage to a total volume of a few hundredths of a cm3. This size reduction introduces many problems. The proposed cold stage volume results in a restriction cross-sectional area of about a thousandth of a mm2 which may cause clogging problems. Flow channels with a cross-sectional area of a few hundredths of a mm2 will produce high pressure drops influencing the JT cycle. Furthermore, the micro channels must be capable of withstanding high pressures and maintaining a large temperature gradient over a relatively short length. The project aim is to develop a reliable micro JT cold stage that is fabricated out of one material with a relatively simple and reproducible fabrication method. The length of the cold stage is calculated at about 20 mm with a width of 1.7 mm and height of about 0.3 mm. The mass flow is in the order of one mg per second to create a net cooling power of 10 mW at 96 K. The final objective of the project is to integrate the cold stage, vacuum chamber and device into one compact design. This paper discusses possible solutions to the problems mentioned and presents a concept design of such a miniature JT cold stage.

An experimental study of low Reynolds number gas flow across pillars in a microchannel is presented. Various geometries of pillars are considered for systematic comparison. This is for the first time such an investigation is done. The pillars 25 um in diameter and height of 230 um are dry etched in silicon. a 4-point pressure drop measurement setup is used to avoid measuring losses in fittings. Among various geometries considered, shifted sine pattern and rhombus shaped structures with an aspect ratio of 1/3 have the lowest friction factor and circle staggered arrangement has the highest friction factor.