Fig. 5: Application in disposable magnetoelectronics.

a Conceptual illustration showing a pathway toward closed-loop eco-sustainability of the biodegradable MR sensors. b Smart package of a medicine box and a gift box. The left two photographs show the closed and open states of the medicine box mounted with a printed Fe/Fe₃O₄-NaCMC sensor and a printed sustainable magnet. Once the medicine box is opened, the state can be recorded by the MR sensor. The right photograph shows a gift box mounted with a printed Fe/Fe₃O₄-NaCMC sensor and a printed sustainable magnet. When the box is opened, the state can be read by the MR sensor, and the circuit control LED light is on. c Magnetoresistance signal variation as the box is closed and open states. d Operational stability test for the printed magnetoresistive sensor under a 100 mT alternating magnetic field cycles. MR performance shows no degradation after 8000 alternating magnetic field cycles. e–h Disposable human machine interface (HMI) application. e, Photograph of the wearable disposable MR sensor printed on the fingernail. A permanent magnetic ring worn on the thumb provides a magnetic field. f A gelatin-glycerol gel encapsulating the printed sensor to protect it from exposure to water. g Photographs of different gestures and the corresponding game operation screenshot, and h the time evolution of the MR signals of the two sensors read out dependent on the distance between the finger nail and the magnetic ring.