Flexible magnetoreceptive switch for on-skin touchless human-machine interaction.

Skin compliant magnetoreceptive electronics is a game changer for prospective human-machine interactions and augmented reality applications [1]. Mechanically flexible magnetoresistive sensors enabled proximity sensing as well as motion and orientation tracking features[2,3] via interaction with magnetic objects. However, current on-skin magnetoreceptors are not yet employed as advanced spintronics-enabled switches and logic elements for skin compliant electronics. The major limitation is the use of in-plane magnetized layer stacks, sensitive mainly to magnetic fields oriented within the sensor plane. Flexible Hall effect sensors[4,5] provide out-of-plane sensitivity but no intrinsic logic, thus requiring more complex electronics. Considering the lower performance of flexible electronics compared to their rigid counterparts[ 6], full-fledged flexible interactive systems should be based on smart receptors with intrinsic logic functionality. Here we present the first mechanically flexible switch based on spin valves sensitive to out-of-plane magnetic fields[7]. The device is realized on a flexible polyethylene naphthalate (PEN) foil and rely on Co/Pd multilayers with perpendicular magnetic anisotropy and synthetic antiferromagnet as a reference layer. By tuning the magnetic coupling strength between the free and the reference layers, the functionality of the device can be tailored between momentary or permanent (latching) switch. The flexible device retains its performance upon bending down to a bending radius of 3.5 mm and withstand more than 600 bendings. We demonstrate the performance of our device as touchless interactive interface for augmented reality systems, as well as its tolerance to the magnetic field disturbances. We showcase the potential of this new kind of flexible magnetoreceptive functional elements as on-skin human-machine interfaces for virtual and augmented reality applications