Highly flexible bismuth Hall sensors on polymeric foils are fabricated, and the key optimization steps that are required to boost their sensitivity to the bulk value are identified. The sensor can be bent around the wrist or positioned on the finger to realize an interactive pointing device for wearable electronics. Furthermore, this technology is of great interest for the rapidly developing market of eMobility, for optimization of eMotors and magnetic bearings.
Being a facet of flexible electronics, mechanically reshapeable magnetic field sensorics enable novel device ideas for soft robotics, interactive devices for virtual- and augmented reality and point of care diagnostics. These applications demand mechanically compliant yet robust sensor devices revealing high sensitivity to small magnetic fields. To push the detection limit of highly compliant and linear magnetic field sensors to be in the sub-µT range, we explore a new fundamental concept for magnetic field sensing, namely the planar Hall effect in magnetic thin films. With their remarkable bendability down to 1 mm, these compliant planar Hall effect sensors allow for an efficient detection of magnetic fields as small as 200 nT with a limit of detection of 20 nT. We demonstrate the application potential of these devices as a direction (angle) as well as proximity (distance) sensors of tiny magnetic fields emanating from magnetically functionalized objects. With their intrinsic linearity and simplicity of fabrication, these compliant planar Hall effect sensors have the potential to become a standard solution for low field applications of shapeable magnetoelectronics in point of care applications and on-skin interactive electronics.
Electronic skins (e‐skins) have established themselves as a versatile technology to restore or enhance human perception, and potentially enable softer robotics. So far, the focus has been mostly on reproducing the traditional functions associated with human skin, such as, temperature, pressure, and chemical detection. New developments have also introduced nonstandard sensing capabilities like magnetic field detection, to spawn the field of magnetosensitive e‐skins. Adding a supplementary information channel—an electronic sixth sense—allows humans to utilize the surrounding magnetic fields as stimuli for touchless interactions. Due to their vectorial nature, these stimuli can be used to track motion and orientation in 3D, opening the door to various kinds of gestural control for interactive devices. This approach to tracking provides an alternative or complement to optic‐based systems, which usually rely on cameras or infrared emitters, that cannot easily capture fine motion when objects are far from the source or the line‐of‐sight is obtruded. Here, the background, fabrication techniques, and recent advances of this field are reviewed; covering important aspects like: directional perception, geomagnetic field detection, on‐site conditioning, and multimodal approaches. The aim is to give the reader a general perspective and highlight some new avenues of research, toward artificial magnetoception.
We employ alternating magnetic fields (AMF) to drive magnetic fillers actively and guide the formation and self-healing of percolation networks. Relying on AMF, we fabricate printable magnetoresistive sensors revealing an enhancement in sensitivity and figure of merit of more than one and two orders of magnitude relative to previous reports. These sensors display low noise, high resolution, and are readily processable using various printing techniques that can be applied to different substrates. The AMF-mediated self-healing has six characteristics: 100% performance recovery; repeatable healing over multiple cycles; room-temperature operation; healing in seconds; no need for manual reassembly; humidity insensitivity. It is found that the above advantages arise from the AMF-induced attraction of magnetic microparticles and the determinative oscillation that work synergistically to improve the quantity and quality of filler contacts. By virtue of these advantages, the AMF-mediated sensors are used in safety application, medical therapy, and human-machine interfaces for augmented reality.