Printable anisotropic magnetoresistance sensors for highly compliant electronics

Abstract

Printed electronics are attractive due to their low-cost and large-area processing features, which have been successfully extended to magnetoresistive sensors and devices. Here, we introduce and characterize a new kind of magnetoresistive paste based on the anisotropic magnetoresistive (AMR) effect. The paste is a composite of 100-nm-thick permalloy/tantalum flakes embedded in an elastomer matrix, which promotes the formation of appropriately conductive percolation networks. Sensors printed with this paste showed stable magnetoresistive properties upon mechanical bending. The AMR value of this sensor is $$0.34\%$$ 0.34 % in the field of 400 mT. Still, the response is stable and allows to resolve sub-mT field steps. When printed on ultra-thin 2.5-$$\upmu \hbox {m}$$ μ m -thick Mylar foil, the sensor can be completely folded without losing magnetoresistive performance and mechanically withstand $$20\, \upmu {\hbox {m}}$$ 20 μ m bending radius. The developed compliant printed AMR sensor would be attractive to implement on curved and/or dynamic bendable surfaces for on-skin applications and interactive printed electronics.

Self-healable printed magnetic field sensors using alternating magnetic fields

“…c Noise signal of sensor. d Comparison of sensitivity, magnetic field where the highest sensitivity is obtained, and figure of merit (FoM) for printable magnetoresistive sensors in previous reports 34 , 41 , 42 , 55 – 61 and this work. Figure of merit is defined as the maximum sensitivity divided by the magnetic field where maximum sensitivity is obtained.…”

“…1b ), although the applied 500 mT was much higher than the above AMF. To assess the AMF-mediated percolation network in magnetoresistive performance, we took a Ni 81 Fe 19 based sensor prepared with thin film technologies as benchmark (e.g., displaying 1.89% magnetoresistance) 34 . The printed AMF-mediated sensor (with 0.91% magnetoresistance at 12.5 mT) reached 48.1% of the performance of the thin film counterpart; while the nanoflake-based sensor without AMF treatment (with 0.1% magnetoresistance at 17 mT) only had 5.3% 32 , even though nanoflakes with larger surface ratios and longer electrical continuity are more desirable for electrical percolation 35 .…”

“…Figure of merit is defined as the maximum sensitivity divided by the magnetic field where maximum sensitivity is obtained. The reported printable sensors were made of 0-dimensional nanoparticles 42 , 55 – 57 , 1-dimensional nanowires 60 , and 2-dimensional nanoflakes 34 , 41 , 58 , 59 , 61 , and based on effects of anisotropic magnetoresistance 34 , giant magnetoresistance 41 , 55 , 58 – 61 , and tunneling magnetoresistance 42 , 56 , 57 . e Photographs and schematic illustrations of different fabrication techniques for printable sensors, and the corresponding magnetoresistance and sensitivity.…”

Dispenser Printed Bismuth‐Based Magnetic Field Sensors with Non‐Saturating Large Magnetoresistance for Touchless Interactive Surfaces

“…[ 10 ] These magnetically sensitive composites have been produced by incorporating ferromagnetic magnetoresistive (MR) particles or flakes dispersed in various binder solutions of gel‐like or thermoplastic nature ( Table 1 ). [ 9–17 ] While these contributions have significantly advanced the field in the last decade, the large‐scale adoption of these technologies remains unfulfilled due to the complexity and high production costs associated with the constituent particles or flakes. Flakes showing giant magnetoresistance effect (GMR) up to 37% consist of multilayered heterostructures that require sequential deposition of sub‐nm‐thick films.…”

“…In response to address the scalability problem of GMR powders, particles from commodity available ferromagnetic materials showing anisotropic magnetoresistance (AMR) were employed. [ 14 ] However, the measured AMR effect was reduced to 0.34%. Moreover, these MR technologies typically have a linear response at magnetic fields below 500 mT and are almost non‐sensitive beyond.…”