A flexible anisotropic magnetoresistance sensor for magnetic field detection

Anisotropic magnetoresistance (AMR) sensors with a flexible substrate are presented in this paper. The AMR sensors were fabricated on polyimide (PI) material in a surface micromachining process, and the minimum linewidth of the sensors was reduced to 3 μm by optimization of the process. An orthogonal-arranged Wheatstone bridge structure was proposed to improve the voltage output, and the AMR strips in series–parallel connection were designed to improve the sensitivity. The AMR sensors with Wheatstone bridge show high linearity, sensitivity, and voltage output performance by measurement. A maximum Wheatstone bridge voltage output of about 0.07 mV was achieved for 0.5 V bias in the magnetic field of 100 Gs, and the sensitivity value of about 1.5 Gs−1 was obtained. Moreover, the AMR sensors had good robustness upon mechanical bending, and a maximum bend radius of about 2.3 cm was achieved. The research results demonstrated the feasibility of manufacturing high-performance small-sized AMR sensors on flexible substrates and showed great potential for magnetic field detection in non-planar applications.