Hartung-Gorre Verlag
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Renate Gorre D-78465
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Scientific Reports on Micro and Nanosystems
edited by Christofer Hierold
Vol. 38
Matthias Alexander Dupuch
Implantable Pressure
Sensor
Encapsulation for
Ventricular
Assist Device Control
1st Edition 2025. (8), XXII, 162 pages. € 64,00.
ISBN 978-3-86628-834-8
Abstract
Autonomous feedback controlled ventricular
assists device (VAD) operation promises a plethora of benefits such as
increased patient safety, comfort, and reduced healthcare costs. Current
generation VADs operate at static pump speeds due to the lack of available
biocompatible, long-term stable pressure sensor systems.
In this thesis, a pressure sensor encapsulation
was developed and integrated in an inflow cannula for a VAD and in an
implantable testing platform for animal trials. The encapsulation uses a media
separating diaphragm embedded in a Parylene C
coating. The approach is expanded to enable optimized diaphragm shapes, which
allow significantly better control over the final device characteristics,
especially the temperature cross sensitivity.
Furthermore, a production processes was
developed to minimize assembly induced internal overpressure.
The produced capsules showed excellent
pressure transmission of more than 99.7 % and a temperature cross sensitivity
of less than 266 Pa from 35 °C to 42 °C for most capsules. However, a large
temperature cross sensitivity was observed from room to body temperature in
some capsules, adding relevant drift of 750 Pa (75 % quartile) after 42 days to
the measurement.
The observed drift is related to the
viscoelastic nature of the Parylene C diaphragm and
the capsule-to-capsule variation is attributed to production process variations,
which can be further optimized.
Systematic errors in the pressure
transmission, temperature cross sensitivity (TCS), and drift were extracted and
correction approaches for each were developed. This enabled the reduction of
the pressure transmission error by 50 % by linear correction. A differential
measurement approach reduced the temperature cross sensitivity to less than 70
Pa from 35 °C to 42 °C and
drastically reduced the temperature induced drift to 300
Pa (75 % quartile) after a jump from room to body temperature. Half of all
sensors even remained within a +- 100 Pa window in the same time period.An alternative drift correction solution was
developed based on the Burgers model for viscoelastic materials. This approach
performed almost as well as the differential correction, but with the added
benefit of being applicable to single sensor systems.
One of the implantable testing platforms was
used in three acute animal trials. It matched the systolic and diastolic
pressures recorded by a catheter tip sensor within a +-
133 Pa window for most
measurements.
The developed solutions and gained
understanding with the proof of concept device build a solid foundation for
future pressure sensor integrations for VAD applications.
Keywords: ventricular assist device (VAD), blood pressure
monitoring, blood pressure sensor, sensor encapsulation, parylene,
drift correction
Scientific Reports on Micro and Nanosystems
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