Passive radiosonde transducer design for remote pressure sensing applications

Abstract

Intracranial pressure can be measured to accuracies within 1 milliTorr using passive microtransponders that are micromachined using silicon as a base technology. These microtransponders can operate with either a dual-oscillator or a phase-locked loop frequency scanned control system. The current work describes the design of a totally implantable microsensor for biomedical applications with the aim to monitor and measure the epidural intracranial pressure . The implanting microsensor is basically an RLC device in which capacitance varies with fluid pressure. The resonant frequency of RLC Series connected device varies with chemically etched diaphragm electrode spacing and thereby measures the variations with pressure changes in the fluid pressure The small pressure changes are recorded by an external receiver unit which drives the implanted sensor into oscillator by means of an RF magnetic field. The pressure measurement system is expected to measure pressure with an accuracy of I Torr over the range 1 to 760 Torr. The microsensor is expected to measure pressure at distances up to 2 meters from the power source loop in any environment that is nonconductive and nonmagnetic. The one application of the present thesis is for the chronic measurement of intercranial fluid pressure following brain surgery and for eschemic brain conditions