Göran Stemme

A valveless diffuser/nozzle-based fluid pump

Abstract A new valveless fluid pump has been designed and tested. The pump consists of two fluid diffuser/nozzle elements on each side of a chamber volume with an oscillating diaphragm. The vibrating diaphragm produces an oscillating chamber volume, which together with the two fluid-flow-rectifying diffuser/nozzle elements, creates a one-way fluid flow. A micropump prototype with a chamber diameter of 19 mm with conical diffuser/nozzle elements has been built and tested. The maximum liquid flow rate is 16 ml/min and the maximum pump pressure is 2 m H 2 O. The pump frequency is of the order of 100 Hz.

Adhesive wafer bonding

Wafer bonding with intermediate polymer adhesives is an important fabrication technique for advanced microelectronic and microelectromechanical systems, such as three-dimensional integrated circuits, advanced packaging, and microfluidics. In adhesive wafer bonding, the polymer adhesive bears the forces involved to hold the surfaces together. The main advantages of adhesive wafer bonding include the insensitivity to surface topography, the low bonding temperatures, the compatibility with standard integrated circuit wafer processing, and the ability to join different types of wafers. Compared to alternative wafer bonding techniques, adhesive wafer bonding is simple, robust, and low cost. This article reviews the state-of-the-art polymer adhesive wafer bonding technologies, materials, and applications.

Resonant silicon sensors

This paper is a review of the design and fabrication of resonant sensors that are based on resonating silicon structures. Some of the design aspects that control the performance of the resonator sensor are analysed. The most important aspects are: resonator materials, fabrication technology, type of resonator, mode of vibration, quality of vibration and temperature stability. Q-factor-reducing damping factors are discussed and the different techniques that are available for excitation and detection of the vibration of the resonator are described. Descriptions of published resonant silicon sensors are presented.

A valve-less planar fluid pump with two pump chambers

A new planar fluid pump based on the valve-less diffuser/nozzle pump principle is presented. The pump consists of two pump chambers, each with two flow rectifying diffuser/nozzle elements with rectangular cross sections, one at the inlet and one at the outlet. The pump chambers are arranged in parallel for high pump flow. Each pump chamber has two piezoelectrically vibrated diaphragms. The planar pump is fabricated in brass with a total thickness of 1 mm. The pump chamber diameter is 13 mm and the diffuser/nozzle element neck dimensions are 0.3×0.3 mm. Simplified theoretical analyses of the maximum pump flow and resonance frequency are given. The flow rectifying ability of the diffuser/nozzle elements is demonstrated in a stationary flow situation and the pump performance is verified in two different pump mode configurations: anti-phase and in-phase chamber volume excitation. The measurements in the anti-phase mode show pump flows and pump pressures which are more than twice as high as those of the in-phase oscillation mode. The anti-phase mode has a pump capacity of about 16 ml/min and a maximum pump pressure of about 1.7 m H2O with the pump diaphragm vibration frequency set to the pump resonance frequency of 540 Hz.

Low-temperature full wafer adhesive bonding

We have systematically investigated the influence of different bonding parameters on void formation in a low-temperature adhesive bonding process. As a result of these studies we present guidelines ...

Micromachined electrodes for biopotential measurements

We describe the microfabrication, packaging and testing of a micromachined dry biopotential electrode, (i.e., where electrolytic gel is not required). It consists of an array of micro-dimensioned, very sharp spikes, (i.e., needles) designed for penetration of human skin which circumvent high impedance problems associated with layers of the outer skin. The spikes are etched in silicon by deep reactive ion etching and are subsequently covered with a silver-silverchloride (Ag-AgCl) double layer. The electrode-skin-electrode impedance of dry spiked electrodes having a size of 4/spl times/4 mm/sup 2/ is reduced compared to standard electrodes using electrolytic gel and having a comparable size. Recorded low amplitude biopotentials resulting from the activity of the brain, (i.e., EEG signals) are of high quality, even for spiked electrodes as small as 2/spl times/2 mm/sup 2/. The spiked electrode offers a promising alternative to standard electrodes in biomedical applications and is of interest in research of new biomedical methods.

Micromachined flat-walled valveless diffuser pumps

The first valveless diffuser pump fabricated using the latest technology in deep reactive ion etching (DRIE) is presented. The pump was fabricated in a two-mask micromachining process in a silicon wafer polished on both sides, anodically bonded to a glass wafer. Pump chambers and diffuser elements were etched in the silicon wafer using DRIE, while inlet and outlet holes are etched using an anisotropic etch. The DRIE etch resulted in rectangular diffuser cross sections. Results are presented on pumps with different diffuser dimensions in terms of diffuser neck width, length, and angle. The maximum pump pressure is 7.6 m H/sub 2/O (74 kPa), and the maximum pump flow is 2.3 ml/min for water.

Micromachined flow-through filter-chamber for chemical reactions on beads

A new flow-through micromachined device for chemical reactions on beads has been designed, manufactured, and characterized. The device has an uncomplicated planar design and microfabrication proces ...

Characterization of micromachined spiked biopotential electrodes

We present the characterization of dry spiked biopotential electrodes and test their suitability to be used in anesthesia monitoring systems based on the measurement of electroencephalographic signals. The spiked electrode consists of an array of microneedles penetrating the outer skin layers. We found a significant dependency of the electrode-skin-electrode impedance (ESEI) on the electrode size (i.e., the number of spikes) and the coating material of the spikes. Electrodes larger than 3/spl times/3 mm/sup 2/ coated with Ag-AgCl have sufficiently low ESEI to be well suited for electroencephalograph (EEG) recordings. The maximum measured ESEI was 4.24 k/spl Omega/ and 87 k/spl Omega/, at 1 kHz and 0.6 Hz, respectively. The minimum ESEI was 0.65 k/spl Omega/ an 16 k/spl Omega/, at the same frequencies. The ESEI of spiked electrodes is stable over an extended period of time. The arithmetic mean of the generated DC offset voltage is 11.8 mV immediately after application on the skin and 9.8 mV after 20-30 min. A spectral study of the generated potential difference revealed that the AC part was unstable at frequencies below approximately 0.8 Hz. Thus, the signal does not interfere with a number of clinical applications using real-time EEG. Comparing raw EEG recordings of the spiked electrode with commercial Zipprep electrodes showed that both signals were similar. Due to the mechanical strength of the silicon microneedles and the fact that neither skin preparation nor electrolytic gel is required, use of the spiked electrode is convenient. The spiked electrode is very comfortable for the patient.

Numerical and experimental studies of flat-walled diffuser elements for valve-less micropumps

An investigation of flat-walled diffuser elements for valve-less micropumps is presented. The diffuser element is a small angle flow channel with a rounded inlet and a preferably sharp outlet. The diverging-wall direction is the positive flow direction. The flow-directing capability under steady flow conditions was determined experimentally for several different diffuser elements. The flow-pressure characteristic was studied in detail for one of them. The result is compared with previously published results on pump performance. Numerical simulations were done using the Computational Fluid Dynamics program ANSYS/Flotran. The simulations show the flow-directing capability of the diffuser elements and predict the flow-pressure characteristics well for Reynolds numbers below 300-400. For higher Reynolds numbers, the simulations show the flow-directing capability, but there is a larger discrepancy between simulations and measurements. Simulations were also done for a nozzle element, a wide-angle flow channel with sharp inlet and outlets used in the micropump with dynamic passive-valves. A nozzle element has the converging-wall direction as positive flow direction. The simulations show differences in the flow patterns for diffuser elements and nozzle elements that explain the opposite positive flow directions. The diffuser element has an ordered flow and takes advantage of the pressure recovery in the diverging-wall direction. The nozzle element has gross flow separation in the diverging-wall direction and there is a vena-contracta effect instead of pressure recovery. The effective cross-sectional area is smaller in the diverging-wall direction than in the converging-wall direction.