B. van der Schoot

Design and fabrication of high-temperature micro-hotplates for drop-coated gas sensors

Note: 243 Reference SAMLAB-ARTICLE-2000-004 Record created on 2009-05-12, modified on 2016-08-08

Integrated flow-regulated silicon micropump

Abstract A piezoelectric silicon micropump with a controlled output flow is presented. A closed-loop controller regulates the liquids flow. The system can maintain a constant output flow when the pressure difference between the pumps output and input varies. This regulation has been demonstrated for flow rates from 10 to 100 μl/min, and for pressure differences up to 100 mbar. The main components of the system as well as the results obtained are discussed.

Smallest dead volume microvalves for integrated chemical analyzing systems

Normally open, normally closed, and three-way microvalves were developed. These microvalves had a simple structure and small dead volume on the order of tens of nl. Each microvalve was driven by a stack-type piezo-actuator and the controllable flow range is from 1 mu l/min to tens of mu l/min. These valves are useful for constructing integrated chemical analyzing systems.<<ETX>>

A Silicon Flow Cell for Optical Detection in Miniaturized Total Chemical Analysis Systems

Abstract The applicability of silicon micromachining to the fabrication of a small-volume flow cell for UV-visible absorption detection is demonstrated. With volumes ranging from 1 to 100 nl and lengths of 1 and 5 mm, this type of cell has a long path length relative to its volume. Light is transported through the cell by means of a series of reflections, so that the optical path length may be increased to values beyond the actual cell length, depending on the input angle of the light. Preliminary experiments using a 1 mm, 15 nl cell to measure dye-containing solutions demonstrate an application of multireflection to the measurement of absorbance.

Nanofluid handling by micro-flow-sensor based on drag force measurements

A micro-flow-sensor for fluids is reported. The flow sensor operates over the 5-500- mu L/min range, allowing the detection of minute volumes, down to nanoliter resolution. The sensing principle is the measurement of the drag exerted by the fluid onto an obstacle, a cantilever beam having overall dimensions of 0.03 mm*1 mm*3 mm. The sensor chip is manufactured with micro-machining technologies, requiring a set of six masks.<<ETX>>

A dipstick sensor for coulometric acid-base titrations

By performing an acid-base titration by coulometric generation of OH− or H+ ions at an inert electrode in close proximity to the pH-sensitive gate of an ISFET, it is possible to determine the acid or base concentration of a solution using the ISFET as an indicator device for the equivalence point in the titration curve. Typical values for the titration time are 0.1 to 10 s for acid or base concentrations ranging from 0.5 × 10−3 to 10 × 10−3 mol/l. By placing the counter electrode for the supplied current on the backside of a small piece of printed-circuit board on which the sensor-actuator is attached, we obtain a dipstick-like structure.

A low-power micromachined MOSFET gas sensor

This paper reports on the design, fabrication, and characterization of the first low-power consumption MOSFET gas sensor, The novel MOSFET array gas sensor has been fabricated using anisotropic bulk silicon micromachining. A heating resistor, a diode used as temperature sensor, and four MOSFETs are located in a silicon island suspended by a dielectric membrane. The membrane has a low thermal conductivity coefficient and, therefore, thermally isolates the electronic components from the chip frame. This low thermal mass device allows the reduction of the power consumption to a value of 90 mW for an array of four MOSFETs at an operating temperature of 170/spl deg/C. Three of the MOSFETs have their gate covered with thin catalytic metals and are used as gas sensors. The fourth one has a standard gate covered with nitride and could act as a reference. The sensor was tested under different gaseous atmospheres and has shown good gas sensitivities to hydrogen and ammonia. The low-power MOSFET array gas sensor presented is suitable for applications in portable gas sensor instruments, electronic noses, and automobiles.

Integrated blood-gas sensor for pO2, pCO2 and pH

Note: 99 Reference SAMLAB-ARTICLE-1993-001 Record created on 2009-05-12, modified on 2016-08-08

Development of a Miniature Bioreactor for Continuous Culture in a Space Laboratory

A new type of miniature bioreactor for continuous culture of yeast cells in space laboratories has been developed. Silicon microtechnology has permitted the integration of numerous functions and systems in a volume of 87 x 63 x 63 mm3 and a weight of 610 g. The 100 ml of fresh medium can be delivered at variable flow rates to the cultivation chamber (volume 3 ml) by means of a micropump. The culture is agitated by a magnetic stirrer. Microsensors monitor pH, temperature and redox potential. The decrease of pH occurring during the cultivation of Saccharomyces cerevisiae is compensated electrochemically. A window allows the inspection of the culture status. Samples of up to 1 ml can be drawn through a silicone rubber septum. The data measured by the sensors are transmitted on-line to the ground station during operations in space. The bioreactor had to fulfil several requirements related to the safety regulation of the space agencies. In particular, new materials had to be selected and tested for their biocompatibility. The instrument has now passed all space and biological qualification tests and will be used in an experiment selected by ESA for the International Microgravity Laboratory-2 Mission in Spacelab in July 1994. This paper gives the results of the functional and biological tests and a detailed description of the instrument.

Characterisation of a fL droplet generator for inhalation drug therapy

A droplet generator for Inhalation Drug Therapy (IDT) was developed which works in the fL size range. The device uses nozzles that are etched through thin membranes by Deep Reactive Ion-etching (DRIE). To analyse the ejection of droplets, high speed video showed to be the most effective. Different ejection regimes were seen as function of the actuation amplitude. To measure the high number of droplets ejected from the final devices, Laser Doppler Anemometry was used. The device as presented showed some of the most critical characteristics required by the FDA and industry.