Touchless Omnidirectional Magnetosensitive Skins for Interactive Electronics

The widespread permeation of electronic devices into our daily life has increased the importance ofseamless interaction schemes that simplify the user’s experience. Electronic skins [1-3] contribute naturally to this development by combining sensor [4,5] and actuator elements in a compliant and mechanically imperceptible [6] format, thus eliminating the need for rigid interfaces. To advance beyond the conventional tactile interactions, we have recently proposed magnetosensitive skins [7-10] as a novel way to interact with objects in a touchless manner. This vision implies that basic building blocks of any interaction like pressing (proximity sensing) or turning (direction sensing) have to be replicated in a touchless format. In order to do so, our methodology utilizes magnetic fields as external stimuli to magnetosensitive circuits which provide a 3D reconstruction of motion in space. Moreover, to expand the breadth of applications, these interactive devices should operate over the whole range of typically available magnetic fields, spanning from the geomagnetic field of 40 μT up to regular permanent magnet fields of ~10 mT.
Here, we introduce a technology platform that addresses this vision to extend the potential of magnetosensitive skins. At its core, the platform utilizes metallic thin films as magnetoresistive (MR) and Hall-effect sensor elements, which are prepared on 6-μm-thick polymeric foils. This combination of out-of-plane (Hall) and in-plane (MR) sensors allows omnidirectional sensing on a single substrate. In addition, by using geometrical modifications like barber poles [11] or measurement schemes like zero-offset anomalous Hall magnetometry [12,13], the output sensitivity and offset can be optimized for a wide variety of applications.
We foresee that these highly compliant magnetic skins could be used to digitize fine motion, e.g. fingers with respect to the palm. This feat could enable the integration of usually rigid magnetic detection systems into on-skin, textilebased or Internet of Things (IoT) applications. A successful implementation could lead to a new class of virtual or augmented reality systems and interactive input devices which extract information from their surroundings through magnetic tags.
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