The design and realization of two pumps based on micromachining of silicon are described. The pumps, which are of the reciprocating displacement type, comprise one or two pump chambers, a thin glass pump membrane actuated by a piezoelectric disc and passive silicon check valves to direct the flow. Chambers, channels and valves are realized in a silicon wafer by wet chemical etching. The results of mechanical calculations and simulations show good agreement with the actual behaviour of the pumps. It is possible to design pumps having a specific yield and pressure dependence, and which are fail-safe (the flow is blocked while the pump is switched off).

.The design, working pnnaple and reahzatlon of an electro-thermopneumatlc liquid pump based on micro-engmeermg techniques are described The pump, which 1s of the reclprocatmg dlsplacement type, comprises a pump chamber, a thm slhcon pump membrane and two s&on check valves to direct the flow The dynamic pressure of an amount of gas contained m a cavity, controlled by reslstlve heating, actuates the pump membrane The cavity, chambers, channels and valves are realized m &con wafers by wet chemical etching Expernnental results are presented Maximum yield and built-up pressure equal 34 $/mm and 0 05 atm, at a supply voltage of 6 V Results of slmulatlons show good agreement with the actual dynarmc behavlour of the pump

The ionic conductivity of single crystals of tysonite-type solid solutions Lal_xBaxFa_x(O • x • 0.095) has been studied parallel and perpendicular to the crystallographic c axis in the temperature range 293-1300 K. Three regions can be discerned in the compositional dependence of the ionic conductivity: (i) the "pure" crystal, in which at room temperature no exchange occurs between different types of anion sites in the tysonite structure; (ii) an intermediate region (0 < x < 7 X 10 -2) which reveals changes in both the conductivity activation enthalpy and the magnitude of the conductivity; (iii) a concentrated solid-solution region (x > 7 X 10-2), where fluoride ions interchange easily among the different anion sublattices. Diffusion coefficients calculated from ionic conductivity results, are in good agreement with those calculated from 19F NMR measurements. Using the present data, along with 19F NMR data, dielectric relaxation data and structural considerations, mechanisms governing the ionic conductivity are proposed.

The structural properties of r.f. planar magnetron sputtered ZnO films are studied as a function of deposition parameters: substrate type, substrate temperature, sputter gas pressure, growth rate and sputtering power.These films are applied as piezoelectric transducers in micromechanical sensors and actuators. The electric properties, and consequently the piezoelectric behaviour, depend strongly on the structural properties of the layers.All films are polycrystalline. The individual grains are highly oriented with their crystallographic c axis perpendicular to the substrate. Crystalline substrates such as silicon or SiO2 induce a growth of small grains, a few hundredths of a micron wide and long. Amorphous substrates such as metals or amorphous SiO2 induce a growth of broad columnar grains extending through the film thickness and a few tenths of a micron wide. Trends in density and grain size are in agreement with Thornton's structure zone model.

A new type of actuator for a microminiature pump is presented. The pressure of air in a cavity, raised by resistive heating, deflects a thin silicon membrane. The dynamics of membrane deflection is studied experimentally, the results being in excellent agreement with simulation. We conclude that the device is suitable as an actuator in a micro-miniature pump.