Skin-conformal flexible and printable magnetoelectronics for human-machine interfaces and soft robotics

Motion sensing is the primary task in numerous disciplines including industrial robotics, prosthetics, virtual and augmented reality appliances. In rigid electronics, rotations, displacements and vibrations are typically monitored using magnetic field sensors prepared on flat and rigid substrates. Extending 2D structures into 3D space relying on the flexible and printed electronics approaches allows to enrich conventional or to launch novel functionalities of spintronic-based devices by tailoring geometrical curvature and 3D shape. We developed shapeable magnetoelectronics [1] – namely, flexible, stretchable [2] and even printable [3] skin-conformal magnetosensitive elements. The technology platform relies on high-performance magnetoresistive and Hall effect sensors fabricated on ultrathin polymeric foils based on thin film technologies or printing methods. These mechanically shapeable magnetosensitive elements enable touchless interactivity with our surroundings based on the interaction with magnetic fields, which is relevant for smart skins, soft robotics and human-machine interfaces. With these activities, we extended the use of high quality magnetic thin films to new research and technology fields. This topic is gaining visibility in the interdisciplinary community of physicists, chemists, mechanical and electrical engineers working on the fabrication of 3D shaped magnetic functional membranes, develops methods for their characterisation and theoretical frameworks for their description as well as puts forth concepts for the technological implementation of shapeable magnetoelectronics in different application fields. Here, we will review technological platforms allowing to realize mechanically imperceptible electronic skins for interactive electronics, which enable perception of the geomagnetic field, but also enable sensitivities down to ultra-small fields of sub-50 nT. These devices allow humans to orient with respect to earth’s magnetic field ubiquitously. Furthermore, biomagnetic orientation enables novel interactivity concepts for virtual and augmented reality applications. We showcase this by realizing touchless control of virtual units in a game using omnidirectional magnetosensitive skins [2]. This concept was further extended by demonstrating a flexible magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [4]. This is crucial for smart home applications, interactive electronics, human-machine interfaces, but also for the realization of smart soft robotics with highly conformal integrated feedback system [5] as well as in medicine for physicians and surgeons. In 2019, we brought these research activities to the next level in the frame of the Helmholtz Innovation Lab FlexiSens. FlexiSens bridges fundamental and application-oriented activities with the focus on the transfer of the thin film fabricated sensor technologies for flexible and printable electronics to the market. For this purpose, together with Scia Systems GmbH, we establish a 300 mm grade production line (thin film deposition, lithography, chemical processing of 300 mm wafers) to bring the our sensor technologies to the industry-relevant scale. Flexible magnetic field sensors are offered to industry partners either directly via the HZDR or via the company HZDR Innovation GmbH and already bring financial benefit to the group. The fundamental and application-oriented aspects of this technology will be discussed in the presentation.

[1] D. Makarov, M. Melzer, D. Karnaushenko, O. G. Schmidt, Applied Physics Reviews, 2016, 3, 011101.
[2] G. S. Cañón Bermúdez, H. Fuchs, L. Bischoff, J. Fassbender, D. Makarov, Nature Electronics, 2018, 1, 589.
[3] M. Ha, G. S. Cañón Bermúdez, T. Kosub, I. Mönch, Y. Zabila, E. S. Oliveros Mata, R. Illing, Y. Wang, J. Fassbender, D. Makarov, Advanced Materials, 2021, 33, 2005521.
[4] J. Ge, X. Wang, M. Drack, O. Volkov, M. Liang, G. S. Cañón Bermúdez, R. Illing, C. Wang, S. Zhou, J. Fassbender, M. Kaltenbrunner, D. Makarov, Nature Communications, 2019, 10, 4405.
[5] M. Ha, G. S. Cañón Bermúdez, J. A.-C. Liu, E. S. Oliveros Mata, B. A. Evans, J. B. Tracy, D. Makarov, Advanced Materials, 2021, 33, 2008751.