Soft-metal bonding-enabled recyclable and anti-interference flexible multilayer piezoelectric sensor for tractor tire strain monitoring

Real-time efficient sensing of machine-soil interactions, especially precise tire-ground contact information, plays a critical role in cultivation, seeding, and harvesting for smart agriculture. However, the complicated agricultural environment poses a considerable challenge to traditional rigid sensors, which cannot suffer from both large deformation and electromagnetic interference. Here, we report a novel soft-metal BiInSn bonding-enabled recyclable and anti-interference flexible multilayer piezoelectric sensor for monitoring tractor tire strain. The printed BiInSn-ink electrode fully wraps the surface fibers of porous BaTiO3/PVDF-HFP electrospun films only through a low pressure at low temperature due to its unique thermal-softening effects, which of the adhesion strength is superior to the intrinsic tension limit of the film. The compact multilayer piezoelectric sensor is thus easily prepared, remarkably increasing the output voltage compared to a single-layer case (up to 300% for three layers). Benefiting from the low melting point of the BiInSn alloy, the sensors are easily recyclable compared to conventional metal electrodes prepared with copper, silver, and gold. In addition, its high electrical conductivity also enables the shielding layer to achieve ultrahigh shielding effectiveness of 2100 dB mm-1. This sensor can be demonstrated for tire strain sensing under complex operating conditions such as plowing, harrowing, and fertilizer application. These findings serve as a foundation for accelerating the development of smart agriculture.