RF micro-electro-mechanical devices for 0.8-2.5 GHz applications in mobile terminals

This thesis presents a wide tuning range micro-electro-mechanical (MEM) capacitor. The two-gap MEM capacitor has a measured nominal capacitance of 1.58 pF and achieves a tuning range of 2.25:1 with parasitic capacitance. When all parasitic capacitance to the substrate are extracted the measured nominal capacitance is 1.15 pF and the tuning range is 2.71:1. The device is made of electroplated gold and has a Q of 66 at 1 GHz, and 53 at 2 GHz. In addition, a novel three-state capacitor is presented. Measured capacitance of the first, the second and the third state are 0.86 pF, 1.61 pF and 3.68 pF, respectively. A novel temperature-compensated two-state microelectromechanical (MEM) capacitor is presented. The principle to minimize temperature dependence is based on geometrical compensation and can be extended to other devices such as continuously tunable MEM capacitors. The compensation structure eliminates the effect of intrinsic and thermal stress on the device operation. This leads to a temperature-stable device without compromising the quality factor (Q) or the voltage behavior. The compensation structure increases the robustness of the devices, but does not require any modifications to the process. Measurement results verify that the OFF and ON capacitance change is less than 6 % and the pull-in voltage is less than 5 % when the temperature is varied from −30 °C to +70 °C. In addition to the temperature stability, the charging of the dielectric layer is studied and a new continuous reliability measurement set-up is presented. This thesis describes important design principles of electrostatically actuated MEM capacitors. Key design principles, such as temperature compensation, calculation of mechanical properties, and calculation of electrical properties of MEM capacitor are studied in detail. A new design principle that describes how pull-in and release voltage ratio is only dependent on up and down capacitance ratio and not on the mechanical properties such as a spring constant is also derived. In addition, it is shown how the RF signal affects the voltage behavior of the MEM capacitor. Two-state, three-state and continuously tunable MEM capacitors are designed and fabricated using presented design principles. Modeling, fabrication and analysis of a truly three-dimensional high-quality-factor toroidal inductor using polymer replication processes is presented. The critical dimensions are in the micrometer range, and the applied manufacturing method is based on the polymer replication. Electrical measurements show that the inductor with an inductance of 6.0 nH exhibits a Q of 37 at 1 GHz and a peak quality factor of 50 at a frequency of 3 GHz. Furthermore, the applied manufacturing technique can be extended to become a flexible packaging platform.reviewe

An Ultrasonically Actuated Needle Promotes the Transport of Nanoparticles and Fluids

Non-invasive therapeutic ultrasound methods, such as high-intensity focused ultrasound (HIFU), have limited access to tissue targets shadowed by bones or presence of gas. This study demonstrates that an ultrasonically actuated medical needle can be used to translate nanoparticles and fluids under the action of nonlinear phenomena, potentially overcoming some limitations of HIFU. A simulation study was first conducted to study the delivery of a tracer with an ultrasonically actuated needle (33 kHz) inside a porous medium acting as a model for soft tissue. The model was then validated experimentally in different concentrations of agarose gel showing a close match with the experimental results, when diluted soot nanoparticles (diameter < 150 nm) were employed as delivered entity. An additional simulation study demonstrated a threefold increase of the volume covered by the delivered agent in liver under a constant injection rate, when compared to without ultrasound. This method, if developed to its full potential, could serve as a cost effective way to improve safety and efficacy of drug therapies by maximizing the concentration of delivered entities within e.g. a small lesion, while minimizing exposure outside the lesion.Comment: 34 pages, 4 figures, under review in the Journal of the Acoustical Society of Americ

An Ultrasonically Actuated Fine-Needle Creates Cavitation in Bovine Liver

Ultrasonic cavitation is being used in medical applications as a way to influence matter, such as tissue or drug vehicles, on a micro-scale. Oscillating or collapsing cavitation bubbles provide transient mechanical force fields, which can, e.g., fractionate soft tissue or even disintegrate solid objects such as calculi. Our recent study demonstrates that an ultrasonically actuated medical needle can create cavitation phenomena inside water. However, the presence and behavior of cavitation and related bioeffects in diagnostic and therapeutic applications with ultrasonically actuated needles are not known. Using simulations, we demonstrate numerically and experimentally the cavitation phenomena near ultrasonically actuated needles. We define the cavitation onset within a liver tissue model with different total acoustic power levels. We directly visualize and quantitatively characterize cavitation events generated by the ultrasonic needle in thin fresh bovine liver sections enabled by high speed imaging. On a qualitative basis, the numerical and experimental results show a close resemblance in threshold and spatial distribution of cavitation. These findings are crucial for developing new methods and technologies employing ultrasonically actuated fine-needles such as ultrasound-enhanced fine-needle biopsy, drug delivery and histotripsy.Comment: 35 pages, 6 figures, under consideration at The Journal of the Acoustical Society of Americ

Non-contact determination of intra-ocular pressure in an ex vivo porcine model

People suffering from glaucoma often endure high intra-ocular pressure (IOP). Methods for determining IOP either contact the eye or are unpleasant to some patients. There is therefore a need for a rapid and patient friendly non-contacting method to determine IOP. To address this need, we developed a tonometer prototype that employs spark-gap induced shock waves and a laser Doppler vibrometer (LDV) that reads the amplitude of membrane waves. The IOP was first identified from the membrane wave propagation velocity first in a custom-made ocular phantom and was then verified in ex vivo porcine eyes. The time-of-flight (TOF) of the membrane wave travelling on a hemispherical membrane was compared to reference IOP values in the sample obtained with an iCare TA01 tonometer. The shock front was characterized by high speed photography. Within one eye, the method achieved an agreement of 5 mmHg (1.96 standard deviation between the shock wave tonometer and the commercial manometer) and high method-to-method association (Pearson correlation, R-2 = 0.98). The results indicate that the presented method could potentially be developed into a non-contacting technique for measuring IOP in vivo.Peer reviewe

Delivery of Agents Into Articular Cartilage With Electric Spark-Induced Sound Waves

Localized delivery of drugs into articular cartilage (AC) may facilitate the development of novel therapies to treat osteoarthritis (OA). We investigated the potential of spark-gap-generated sound to deliver a drug surrogate, i.e., methylene blue (MB), into AC. In vitro experiments exposed bovine AC samples to either simultaneous sonication and immersion in MB (Treatment 1; n = 10), immersion in MB after sonication (Control 1; n = 10), solely immersion in MB (Control 2; n = 10), or neither sonication nor immersion in MB (Control 3; n = 10). The sonication protocol consisted of 1,000 spark-gap -generated pulses. Delivery of MB into AC was estimated from optical absorbance in transmission light microscopy. Optical absorbance was significantly greater in the treatment group up to 900 μm depth from AC surface as compared to all controls. Field emission scanning electron microscopy (FESEM), histological analysis, and digital densitometry (DD) of sonicated (n = 6) and non-sonicated (n = 6) samples showed no evidence of sonication-induced changes in proteoglycan content or collagen structure. Consequently, spark-gap -generated sound may offer a solution for localized drug delivery into AC in a non-destructive fashion. Further research on this method may contribute to OA drug therapies

Ultrasound-enhanced electrospinning

Electrospinning is commonly used to produce polymeric nanofibers. Potential applications for such fibers include novel drug delivery systems, tissue engineering scaffolds, and filters. Electrospinning, however, has shortcomings such as needle clogging and limited ability to control the fiber-properties in a non-chemical manner. This study reports on an orifice-less technique that employs high-intensity focused ultrasound, i.e. ultrasound-enhanced electrospinning. Ultrasound bursts were used to generate a liquid protrusion with a Taylor cone from the surface of a polymer solution of polyethylene oxide. When the polymer was charged with a high negative voltage, nanofibers jetted off from the tip of the protrusion landed on an electrically grounded target held at a constant distance from the tip. Controlling the ultrasound characteristics permitted physical modification of the nanofiber topography at will without using supplemental chemical intervention. Possible applications of tailor-made fibers generated by ultrasound-enhanced electrospinning include pharmaceutical controlled-release applications and biomedical scaffolds with spatial gradients in fiber thickness and mechanical properties.Peer reviewe

Lapsena sydänleikkauksella hoidettujen ennuste on parantunut

Lievissä sydänvioissa elinajanodote vastaa normaaliväestön tasoa. Sydämen vajaatoiminta ja äkkikuolemat ovat vähentyneet merkittävästi vuoden 1990 jälkeen leikatuilla potilailla. Aortan koarktaation leikkauksen jälkeisiä pitkäaikaisongelmia ovat kohonnut verenpaine sekä rekoarktaatio. Fallot’n tetralogian ja yksikammioisen sydämen vuoksi leikatuilla potilailla yleisiä ovat takyarytmiat ja sydämen vajaatoiminta. Valtasuonten transpositiossa eteistunnelointiin liittyvät rytmihäiriöt ja sydämen vajaatoiminta ovat vähentyneet merkittävästi uuden valtasuonten vaihtoleikkauksen myötä. Potilaat tarvitsevat sydämen seurantaa sekä tehokasta liitännäissairauksien primaarista ja sekundaarista ehkäisyä.Peer reviewe