Dispenser printed bismuth-based magnetic field sensors with non-saturating large magnetoresistance for touchless interactive surfaces

Printed magnetic field sensorics enable a new generation of human-machine interfaces and contactless switches for resource efficient printed interactive electronics. As printed magnetoresistors rely on scarce or hard to manufacture magnetosensitive powders, their scalability and demonstration of printing with industry-grade technologies are the key material science challenges. Here, we report dispenser printing of a commodity scale nonmagnetic bismuth-based paste processed by large area laser sintering to obtain printed magnetoresistive sensors. The sensors are printed on different substrates including ceramics, paper and polymer foils. We validate experimentally that the peculiar quantum large orbital magnetoresistive effect remains effective in printed bismuth sensors, allowing their operation in high magnetic fields. The sensors reveal up to 146% resistance change at 5 T at room temperature with a maximum resolution of 2.8 µT. If printed on flexible foils, our sensors show resilience to bending deformation for more than 2000 bending cycles and withstand even thermal forming, as relevant for smart wearables and in-mold electronics. The freedom in the substrate choice and sensor design enabled by dispenser printing allowed us to implement the proposed sensor technology for different applications focused on touchless interactive platforms, such as advertisement materials, interactive wallpapers and printed security panels.