Integrated sensors for process monitoring and health monitoring in microsystems

This thesis presents the development of integrated sensors for health monitoring in Microsystems, which is an emerging method for early diagnostics of status or “health” of electronic systems and devices under operation based on embedded tests. Thin film meander temperature sensors have been designed with a minimum footprint of 240 m × 250 m. A microsensor array has been used successfully for accurate temperature monitoring of laser assisted polymer bonding for MEMS packaging. Using a frame-shaped beam, the temperature at centre of bottom substrate was obtained to be ~50 ºC lower than that obtained using a top-hat beam. This is highly beneficial for packaging of temperature sensitive MEMS devices. Polymer based surface acoustic wave humidity sensors were designed and successfully fabricated on 128° cut lithium niobate substrates. Based on reflection signals, a sensitivity of 0.26 dB/RH% was achieved between 8.6 %RH and 90.6 %RH. Fabricated piezoresistive pressure sensors have also been hybrid integrated and electrically contacted using a wire bonding method. Integrated sensors based on both LiNbO3 and ZnO/Si substrates are proposed. Integrated sensors were successfully fabricated on a LiNbO3 substrate with a footprint of 13 mm × 12 mm, having multi monitoring functions for simultaneous temperature, measurement of humidity and pressure in the health monitoring applications

On the Ground State and Evolution of Structural and Transport Properties of Tin Selenide

The recent surge of interest in tin selenide (SnSe) is due to the reported record-high thermoelectric figure of merit at elevated temperatures. While the researchers are exerting tremendous efforts to further improve the thermoelectric performance of SnSe via doping and nanostructuring, it is getting more and more apparent that SnSe is fascinating in many aspects of fundamental physics. SnSe is, in many aspects, an outlier of the current materials selection rules for high thermoelectric performance. Hence, answering why thermoelectric performance is high in SnSe should come before addressing how to further improve its thermoelectric performance. To this end, there are three primary questions worth immediate attention, one related to the thermal nature of SnSe: (i) why the lattice thermal conductivity is low in such a simple-structured light element containing binary compound; and the other two related to the electrical nature of SnSe: what is the electronic ground state of this material. The second question can be addressed by answering to sub-questions: (ii) what is the origin of the resistivity anomaly around 50 K; and (iii) what is the nature of the metal-insulator transition driven by Sn deficiency. In this thesis, we intend to address the three questions by means of the temperature dependent resistivity, Seebeck coefficient, Hall coefficient, specific heat, thermal conductivity, magnetic susceptibility and X-ray diffraction measurements in conjunction with density functional theory calculations. These results presented a grand picture how SnSe evolves structurally, electrically, and thermally from a low temperature metallic state to a high temperature semiconducting state toward a promising thermoelectric performance. In particular, we found that (i) high quality pristine SnSe single crystals exhibit a metallic ground state (that is, a small but robust Fermi surface with multiple pockets) with a coexisting band gap; (ii) off-stoichiometry and doping could destabilize the metallic state; (iii) the low-lying optical phonon modes and strong anharmonicity contribute to the low lattice thermal conductivity. We obtained a thermoelectric figure of merit ZT ∼ 1.0, ∼ 0.8 and ∼ 0.25 at 850 K along the b, c and a directions in high quality single crystalline SnSe. We have also discussed the formation of the Fermi surface in relation to Sn vacancies and the disorder induced metal-to-insulator transition in light of Anderson localization

Naked-Eye Detection of Hepatitis B Surface Antigen Using Gold Nanoparticles Aggregation and Catalase-Functionalized Polystyrene Nanospheres

Developing rapid, efficient, highly sensitive, simple, stable, and low-cost virus marker detection products that are appropriate for basic facilities is of great importance in the early diagnosis and treatment of viruses. Naked-eye detection methods are especially important when medical testing facilities are limited. Polystyrene nanospheres (PSs) with catalytic and specific recognition functions were successfully developed by simultaneously modifying catalase and goat anti-hepatitis B surface antibodies on nanospheres. The modified PSs contributed significantly to the amplification of the signal. Via the specific antigen–antibody reaction, the bifunctional nanospheres could be captured on microplate and then catalyzed the decomposition of hydrogen peroxide to reduce chloroauric acid and synthesize gold nanoparticles (AuNPs). Due to the surface plasmon resonance of AuNPs, the solution color change could be observed with the naked eye and the limit of detection (LOD) was 0.1 ng/mL. Furthermore, the LOD observed with instrumentation was 0.01 ng/mL, which meant that a rapid, efficient, and highly sensitive method for the detection of hepatitis B surface antigens was successfully developed, and neither complex sample pretreatment nor expensive equipment was needed

Autonomous pointing control of a large satellite antenna subject to parametric uncertainty

With the development of satellite mobile communications, large antennas are now widely used. The precise pointing of the antenna’s optical axis is essential for many space missions. This paper addresses the challenging problem of high-precision autonomous pointing control of a large satellite antenna. The pointing dynamics are firstly proposed. The proportional–derivative feedback and structural filter to perform pointing maneuvers and suppress antenna vibrations are then presented. An adaptive controller to estimate actual system frequencies in the presence of modal parameters uncertainty is proposed. In order to reduce periodic errors, the modified controllers, which include the proposed adaptive controller and an active disturbance rejection filter, are then developed. The system stability and robustness are analyzed and discussed in the frequency domain. Numerical results are finally provided, and the results have demonstrated that the proposed controllers have good autonomy and robustness