Printable anisotropic magnetoresistance sensors for highly compliant electronics

Abstract

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 $$0.34\%$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>0.34</mml:mn> <mml:mo>%</mml:mo> </mml:mrow> </mml:math> 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- $$\upmu \hbox {m}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mtext>m</mml:mtext> </mml:mrow> </mml:math> -thick Mylar foil, the sensor can be completely folded without losing magnetoresistive performance and mechanically withstand $$20\, \upmu {\hbox {m}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>20</mml:mn> <mml:mspace/> <mml:mi>μ</mml:mi> <mml:mtext>m</mml:mtext> </mml:mrow> </mml:math> 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.