Magnetic field-assisted self-assembled aligned nanowires for anisotropic strain sensor with ultrahigh resolution

Abstract

Flexible anisotropic strain sensors (ASSs) are crucial for comprehending both the magnitudes and directions of complex strains. Some fabrication techniques have been employed to engineer macro-alignments of sensing materials capable of an anisotropic response to strain. However, these sophisticated processes often fail to precisely control the micro-assembly of sensing elements, thereby limiting the sensors’ ability in accurately discerning strains below 0.1 %. Here, we propose an ASS based on an aligned magnetic nanowire array (AMNWA). During the fabrication of AMNWAs, an external magnetic field facilitates the alignment of nanowires in a specific direction, while micro fields of nanowires further induce the construction of end-to-end junctions between nanowires, whose conductivity is susceptible to minimum strains. Consequently, the AMNWA demonstrates a remarkable sensitivity to strains parallel to the aligned direction (Gauge factor > 500), allowing the ASS for the discernment of subtle strains as minuscule as 0.0037 % with a theoretical resolution of 0.001 %. The response of the AMNWA presents extreme anisotropy, with negligible sensitivity to strains perpendicular to the aligned direction. By strategically arranging two AMNWAs orthogonally, the magnitude and direction of complex strains can be effectively decoupled. Notably, this configuration enables accurate recognition of strain signals generated by human joint movements. According to these excellent sensing performances, we hold an optimistic outlook on the potential inspiration and reference of AMNWAs for the design and optimization of ASSs.