Project A2 - Hybrid Magnetoelectric Sensors Based on Mechanically Soft Composite Materials

The project aims to develop novel magnetoelectric (ME) sensors that are not based on conventional magnetostrictive and piezoelectric materials but involve new material concepts for the efficient conversion of the magnetic field change into an electric signal. We use composite cantilevers and pursue two key strategies:

• Reduction of passive materials and components, in particular the substrate is eliminated or the substrate effect is drastically reduced by a minimalistic sensor design.
• The energy for bond stretching is minimized by employment of very soft materials for the magneto- and electroactive components.

In the first funding period, both strategies were successfully implemented. Clamp-free mechanically soft magnetostrictive composite cantilevers with a bending at saturation of almost 5° and an order of magnitude higher piezomagnetic coefficient (compared to, e.g. conventional metglas) were developed, and the potential of soft and non-clamped materials as an alternative magnetostrictive component was clearly demonstrated. Moreover, the piezoelectric material was completely removed in the sensor design and replaced by an electret generator/transducer setup, which enabled very compact and simplified cantilever sensors. Here, we also introduced a new approach to soften the vibrating beam by reduction of the restoring force through the attractive electrostatic electret potential. This approach increases the oscillation amplitude while reducing the resonance frequency and simultaneously gaining bandwidth. Accordingly, the electrostatic interaction enables direct detection of magnetic fields with a large bandwidth.

In the second funding period, we plan to extend our demonstrated electret generator/transducer principle for the development of hybrid ME sensors based on mechanically soft composite materials. Emphasis will now shift from first feasibility studies to advanced designs and low limits of detection. In order to increase the sensitivity, we intend to maximize the total chargeable electret surface by using highly porous materials as templates. In this approach, a thin film dielectric fluoropolymer will be deposited onto the porous template by initiated chemical vapor deposition (iCVD) combined with a subsequent corona discharge treatment. iCVD in conjunction with corona discharge already turned out to enable unique deposition of ultra-stable fluoropolymer electret thin films. Especially the growth characteristics typical for CVD and low process temperature of iCVD permit the deposition on the complex and temperature sensitive substrates envisioned here. A custom-made setup based on syringe pumps allows 3D printing of complex resonator geometries, which are made up of mechanically soft composites, e.g. silicone, filled with magnetic micro- and nanoparticles. Thus, the unique combination of sensor fabrication methods provides design freedom for the individual components with micro scale precision in 3D for the optimum tailoring of the potential energy landscape of the ME resonators by the targeted employment of non-linearities like progressive characteristics or attractive potentials. The developed sensors will allow direct measurements with a large bandwidth, particularly in the range of 10 - 40 Hz for applications in magnetocardiography.

Involved Researchers

Person		Role
	Prof. Dr. Rainer Adelung Materials Science Functional Nanomaterials	Project lead
	Prof. Dr. Franz Faupel Materials Science Multicomponent Materials	Project lead
	Dr. Sören Kaps Materials Science Functional Nanomaterials	Project lead
	Dr.-Ing. Stefan Schröder Materials Science Multicomponent Materials	Doctoral researcher
	Dr. Thomas Strunskus Materials Science Multicomponent Materials	Associated project lead
	M.Sc. Lukas Zimoch Materials Science Functional Nanomaterials	Doctoral researcher

Role within the Collaborative Research Centre

Cooperate with the following projects:

Project-related Publications

S. Schröder, N. Ababii, O. Lupan, J. Drewes, N. Magariu, H. Krüger, T. Strunskus, R. Adelung, S. Hansen, F. Faupel: Sensing Performance of CuO/Cu2O/ZnO: Fe Heterostructure Coated with Thermally Stable Ultrathin Hydrophobic PV3D3 Polymer Layer for Battery Application, Materials Today Chemistry, vol. 23, pp. 100642, 2021.

A. Komijani, S. Schröder, T. Strunskus, F. Faupel: Multi-pin Corona Poling Rotating System for ME Electret Sensors, 18th IEEE International Symposium on Electrets (ISE 18), Shanghai, China, 24-28 September, 2021.

S. Schröder, A. M. Hinz, T. Strunskus, F. Faupel: Molecular Insight into Real-Time Reaction Kinetics of Free Radical Polymerization from the Vapor Phase by In-Situ Mass Spectrometry, J. Phys. Chem. A., 125, pp. 1661−1667, 2021.

M. H. Burk, D. Langbehn, G. Hernández Rodríguez, W. Reichstein, J. Drewes, S. Schröder, S. Rehders, T. Strunskus, R. Herges, F. Faupel: Synthesis and Investigation of a Photoswitchable Copolymer Deposited via Initiated Chemical Vapor Deposition for Application in Organic Smart Surfaces, ACS Appl. Polym. Mater., 3, 3, 1445–1456, 2021.

S. Schröder, O. Polonskyi, T. Strunskus, F. Faupel: Nanoscale Gradient Copolymer Films Via Single-Step Deposition from the Vapor Phase, Materials Today, vol. 37, pp. 35-42, 2020.

M. H. Burk, S. Schröder, W. Moormann, D. Langbehn, T. Strunskus, S. Rehders, R. Herges, F. Faupel: Fabrication of Diazocine-Based Photochromic Organic Thin Films via Initiated Chemical Vapor Deposition, Macromolecules, vol. 53, issue 4, pp. 1164–1170, 2020.

M. Scharnberg, S. Rehders, Ö. Adiyaman, S. Schröder, T. Strunskus and F. Faupel: Evaporated Electret Films with Superior Charge Stability Based on Teflon AF 2400, Organic Electronics, vol. 70, pp. 167-171, 2019.

S. Schröder, T. Strunskus, S. Rehders, K. K. Gleason, F. Faupel: Tunable Polytetrafluoroethylene Electret Films with Extraordinary Charge Stability Synthesized by Initiated Chemical Vapor Deposition for Organic Electronics Applications, Scientific Reports, 9, no. 2237, 2019.

M. Mintken, M. Schweichel, S. Schröder, S. Kaps, J. Carstensen, Y. K. Mishra, T. Strunskus, F. Faupel, R. Adelung: Nanogenerator and Piezotronic Inspired Concepts for Energy Efficient Magnetic Field Sensors, Nano Energy, vol. 56, pp. 420-425, 2019.

O. C. Aktas, S. Schröder, S. Veziroglu, M. Z. Ghori, A. Haidar, O. Polonskyi, T. Strunskus, K. K. Gleason, F. Faupel: Superhydrophobic 3D Porous PTFE/TiO2 Hybrid Structures, Advanced Materials Interfaces, vol. 6, 1801967, 2019.