Piezoelectric Hydrocephalus Shunt Valve – Design and First Evaluation Results
P.P. Pott, G. Allevato, M. Bartenschlager, J. Butz, P. Schmitt, H.F. Schlaak
Technische Universität Darmstadt, Darmstadt, Germany
Excess production and / or impeded drain of Liquor Cerebrospinalis can lead to increased intracranial pressure (ICP) resulting in pain and severe damage to the brain. A possible therapy is the use of shunt valves that control the drain of the liquor to the abdominal cavity. Conventional valves distinguish between supine and standing position and use pre-defined default pressure values. In advanced systems, the pressure can be defined from outside the cranium using external programming devices. However, default pressure changes during daytime activity cannot be considered eventually leading to headache and dizziness. A user-programmable mechatronic
valve would be advantageous to overcome these limitations.
Requirements concerning size, pressure range, electromagnetic compatibility, robustness against external acceleration, and power consumption have to be met. Above all, safety has to be ensured at all times by providing a fail-safe state in case of malfunction and power shortage.
To meet these requirements, a system consisting of a conventional spring-loaded ball-in-cone valve and a piezoelectric bending actuator is proposed. Here, the actuator is used to raise the preload of the spring above the fail safe level. To maintain a certain preload with the piezoelectric actuator, only charge losses have to be delivered by the energy source. The internal electronics are based on a new integrated circuit charge pump to alter the battery voltage to meet the voltage requirements of the piezo element while avoiding any inductance.
First evaluation shows that the opening pressure can be controlled with 6 bit. Biocompatibility as well as compatibility with an MR environment can be derived by making the housing from PEEK and by using glass for the valve ball and PEEK springs.
ACTUATOR 2016 Manuscript B1.3
Publication date: 01/06/2016
Manuscript B1.3 published in Conference Proceedings ACTUATOR 2016
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