• Organisation

Abstract:

The present work focuses on the design, realization and test of a miniaturized piezoresistive force sensor. The application expects the integration on the top of a guide wire for catheterization in minimal-invasive surgery. Furthermore, a method for packaging the measuring element is investigated.

In accordance with its application for catheterization, the choice of the most suitable sensor is mainly dictated by the need of an element which can be integrated in a standard guide wire whose diameter is 360 µm. In order to select the most suitable element, several possibilities are evaluated and compared. Since the chosen element is not available for test and measurements, a corresponding model is required for the experiments. The model construction consists of modifying a standard piezoresistive pressure sensor through a grinding process. After the description of the method used to manufacture models of the chosen element, the investigation of the covering technique and materials follows. Sensors covered with silicone and polyurethane are studied and tested. The measurements consist in the determination of the static and dynamic transfer factors as well as phase shift with forces in the span of 0-50 mN and frequencies up to 80 Hz. Since covered and uncovered sensors are compared, the influence of the cover on the characteristics of the sensors is shown as well.

The results of the measurements are conditioned by strong temperature dependence, up to 0.12 - 0.15%/°C respectively for polyurethane and silicone and even 0.275%/°C in case of uncovered sensors. The temperature dependence is caused by the absence of the integrated Wheatstone bridge, which is lost after the mechanical modifications of the sensor.

The static measurements show transfer factors ranging from 0.35 mV/mN up to 4.2 mV/mN respectively for covered and uncovered sensors.

The dynamics results show transfer factors differences between -3 dB to +3 dB in comparison to the quasi-static ones. The phase shift of uncovered sensor remains smaller than 10° while covered sensors show phase lag up to ±25°.

Despite the low repeatability of the results due to a limited number of measurements and a significant drift, this thesis demonstrates the potential of the chosen element as a force sensor for catheterization and ends with suggestions of how such a sensor can be improved in the near future.

EMK-spezifische Daten:

Lagerort Dokument: Archiv EMK, Kontakt über Sekretariate,

Bibliotheks-Sigel: 17/24 EMKD 1583

Art der Arbeit: Diplomarbeit

Beginn Datum: 09-03-2005

Ende Datum: 19-09-2005

Querverweis: keiner

Studiengang: Elektrotechnik und Informationstechnik (ETiT)

Vertiefungsrichtung: Mikro- und Feinwerktechnik (MFT)

Abschluss: Diplom (MFT)