Silicone-based sensor elements for actively-deformable, hydraulically-actuated medical products (Akva-Med Sense)

Prof. L. Zentner
Dr. S. Griebel

The aim of the previous project (Akva-Med) was to develop compliant fluid-mechanical actuators that can be specifically deformed by external control. They are used in flexible implants or diagnostic and therapeutic instruments. As an exemplary application, electrode carriers have been chosen, which are inserted with low-contact preferably into the twisted structure of the cochlea (hearing auger). By means of a targeted, continuous adaptation of the electrode curvature, a gentle implantation with a perimodiolar end position can be achieved.

For the development of the actuators, a model-based synthesis method was developed that combines the finite element method and the analytical method. Conducted scaling examinations showed that geometrically similar hollow-cylindrical rods with embedded thread and with identical material and internal pressure achieve a geometrically similar shape. This finding enabled the theoretical and experimental investigations to be carried out on an enlarged scale.

Two types of actuators (in the initial state straight and pre-curved actuators) could be proved that the desired deformations of the actuators can be achieved. This could be used to verify the developed synthesis process. Furthermore, experimental insertion experiments on the scaled cochlear model showed that the insertion forces acting on the cochlea during the insertion can be reduced.

The aim of the project is the consequential suupplement of the instruments developed in the previous project by an integrated sensor system for the detection of deformation states and / or interaction forces with the surrounding tissues.
In order to obtain the advantageous compliance of the developed actuators, electrically conductive silicones are to be used. These are as flexible as the basic material used for the instruments or the already developed actuators. Furthermore, conductive polymers change their electrical resistance as a function of the material elongation, whereby an inherent sensor system can be realized in the silicone-based instrumentation.

Within the follow-up project, the possibilities and limitations of compliant sensor technology shall be investigated. The focus are the identification of relevant design parameters, which must be taken into account in the design process of sensory areas, as well as the development of an analytical-model-based synthesis method for inherent sensor technology. This also includes the establishment of necessary methods for shaping, structuring and contacting the sensor elements. Due to the scaling of the instrumentation, embodied as a compliant rod-shaped fluid-mechanical actuator (FMA), within the framework of modeling, differently sized instruments are considered. This is intended to exploit the limits of miniaturization. Afterwards, the fundamentals developed in the project will also form a basis for sensorized, fluidically actuated compliant endoscopes and catheters and thus for further surgical applications.

• Link to the video on youtube.com: detailed video
• Link to the video on youtube.com: shortened video
• previous project Akva-Med

• Griebel, S.: Entwicklung und Charakterisierung fluidmechanischer nachgiebiger Aktuatoren am Beispiel eines multifunktionalen Sauggreifers. In: Berichte der Ilmenauer Mechanismentechnik Band 6, Universitätsverlag Ilmenau, Ilmenau, 2021, ISBN: 978-3-86360-233-8; doi: 10.22032/dbt.46923
• Zentner, L.; Linß, S.: Compliant Systems - Mechanics of elastically deformable mechanisms, actuators an sensors. Berlin/Boston: De Gruyter, 2019 – ISBN: 978-3-11-047731-3
• Zentner, L.; Griebel, S. und Hügl, S.: „Fluid-mechanical compliant actuator for the insertion of a cochlear implant electrode carrier“. In: Mechanism and Machine Theory 142, Nr. 103590, S. 1–16. issn: 0094114X. doi: 10.1016/j.mechmachtheory.2019.103590, 2019.
• Zentner, L.; Griebel, S.; Wystup, C.; Hügl, S.; Rau, T. S., Majdani, O.: Synthesis process of a compliant fluidmechanical actuator for use as an adaptive electrode carrier for cochlear implants. In: Mechanism and Machine Theory 112, S. 155–171. issn: 0094114X. doi:10.1016/j.mechmachtheory.2017.02.001, 2017.
• Griebel, S.; Hügl., S.; Rau, T.S.; Majdani, O.; Zentner, L.: Nachgiebiger fluidmechanischer Aktuator für eine schonende Implantation am Beispiel eines vorgekrümmten Cochlea-Implantat-Elektrodenträgers. In: 12. Kolloquium Getriebetechnik, 18 - 20 September 2017 in Dresden, S. 235-254, TUDpress, 2017.
• Hügl, S.; Zentner, L, Griebel, S., .; Majdani, O.; Rau, T. S.: Analysis of the customized implantation process of a compliant mechanism with fluidic actuation used for cochlear implant electrode carriers. In: Scharff,Peter (Hrsg.): 59th IWK, Ilmenau Scientific Colloquium, Technische Universität Ilmenau, 11.-15. September 2017 Proceedings, 6 Seiten, Ilmenau, 2017.
• Hügl, S.; Zentner, L.; Griebel, S.; Majdani, O.; Lenarz, T.; Rau, T. S.: Individualized design of fluidically actuated cochlear implants. In: 51. Jahrestagung der Biomedizinischen Technik und Dreiländertagung der Medizinischen Physik (BMTMedPhys), Dresden, 2017.09.10, S. 280, doi: doi.org/10.1515/bmt-2017-5054, 2017.

• Griebel, S.; Hügl., S.; Rau, T. S.; Majdani, O.; Wystup, C.; Lenarz, T.; Zentner, L.:
  Adaptive electrode carrier
  Aktenzeichen: WO 2017 / 148903 A1, published on 08.09.2017
• Griebel, S.; Hügl., S.; Rau, T.S.; Majdani, O.; Wystup, C.; Lenarz, T.; Zentner, L.:
  Adaptiver Elektrodenträger, seine Verwendung und Verfahren zu seiner Insertion
  Aktenzeichen: DE 10 2016 003 295.B3, patent granted on 11.05.2017

Dr.-Ing. Thomas S. Rau, Medizinische Hochschule Hannover, Klinik für Hals-, Nasen-, Ohren-Heilkunde

08/2017 - 12/2020

DFG - Deutsche Forschungsgemeinschaft ; Project: https://gepris.dfg.de/gepris/projekt/241357279
DFG - reference number: ZE 714/9-2