This paper deals with the characteristics of circular shaped polysilicon pressure sensor diaphragms operating in the non-tactile mode. Using a phase shifting interferometer the main characteristics of diaphragms were investigated under applied pressure with respect to sensitivity, initial deflection and cavity height. Diaphragms with a thickness of 1 μm and a diameter of 96 μm were investigated in an intended pressure range of applied pressure of about 700 – 2000 hPa. Process parameters with major impact on performance and yield limitations were identified. These include the variance in diaphragm sensitivity and the impact of the variance of the sacrificial oxide layer defining the diaphragm cavity height on the contact pressure point. The sensitivity of these diaphragms including the variance was found to be - 19.8 ± 1.3 nm per 100 hPa. The impact of variance in the cavity height on the contact pressure point was found to be about 3.7 ± 0.5 hPa per nm. Summarizing both impacts a maximum variation of the contact pressure point of more than 450 hPa is possible to occur considering a nominal deflection of 300 nm. By optimizing the process of diaphragm deposition the variance in the sensitivity of the diaphragm was decreased by a factor of 2. A semi – empirical formula was evaluated that describes the deflection including initial deflection due to intrinsic stress and the process variations. A validation to the experimental obtained deflection lines showed a good agreement with deviations of less than 2 % for radial ranges of maximum deflection.
In view of their properties, laser-driven ion beams have the potential to be employed in innovative applications in the
scientific, technological and medical areas. Among these, a particularly high-profile application is particle therapy for
cancer treatment, which however requires significant improvements from current performances of laser-driven
accelerators. The focus of current research in this field is on developing suitable strategies enabling laser-accelerated
ions to match these requirements, while exploiting some of the unique features of a laser-driven process. LIBRA is a
UK-wide consortium, aiming to address these issues, and develop laser-driven ion sources suitable for applicative
purposes, with a particular focus on biomedical applications. We will report on the activities of the consortium aimed to
optimizing the properties of the beams, by developing and employing advanced targetry and by exploring novel
acceleration regimes enabling production of beams with reduced energy spread. Employing the TARANIS Terawatt
laser at Queen's University, we have initiated a campaign investigating the effects of proton irradiation of biological
samples at extreme dose rates (> 109 Gy/s).
A system-level model of an electrostatically actuated accelerometer is presented. The accelerometer comprises a proof mass levitated between an arrangement of upper and lower pie-shaped electrodes. The proof mass is an electroplated nickel disk, 1 mm in diameter and 200 micrometers thick. The position and orientation of the disk is detected by measuring the differential capacitance between the disk and each of the four upper and corresponding lower electrodes.
This paper reports the design, fabrication and testing of silicon based micropump for liquid and gases. This piezoelectrically driven membrane pump is designed to be tolerant to gas-bubbles and to be suitable for self-priming. Reducing the dead volume within the pump, and thus increasing the compression ration, achieves the gas pumping. The main advantage of the pump described in the paper is the self-aligning of the membrane unit to the valve unit and the possibility of using screen printed PZT as actuator, which enables mass production and thus very low-cost micropumps. Dynamic passive valves are used, as those valves are very reliable having no moving parts and being not sensitive to smaller particles. Furthermore they can follow high frequencies, hence allowing the pump to run at resonance frequency enabling the maximum deflection of the diaphragm. First tests carried out on the micropump have produced promising results.