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