Research On Preparation And Performance Of Flexible Magnetic Field Sensor Based On C₆₀@Fe₃O₄ Nanocomposite

With the development of flexible electronic devices,the application range of flexible sensors has become wider and wider.It includes force sensors,temperature sensors,humidity sensors,and so on.At present,flexible magnetic field sensor has also begun to attract people's attention.Most magnetic sensors are rigid sensors.In order to adapt to complex detection environments and mechanical deformations,future equipment requires magnetic sensors to have excellent flexibility and stretchability.Therefore,research on flexible magnetic field sensors is imminent.Many researchers have realized the preparation of flexible magnetic field sensors based on different mechanisms such as piezoelectric,triboelectric,and stress.They also have explored their response principles.However,there are still many problems in the current research in this field.The sensitivity,repeatability,and response time of flexible magnetic field sensors do not meet the requirements of practical applications.Research on the selection of magnetically sensitive materials,the structure of the sensor,and the response mechanism of the sensor are also not mature.Therefore,to prepare a magnetically sensitive material with good dispersion and superparamagnetism,and optimizing the structure of the sensor will improve the performance of the sensor.In this paper,in response to the high requirements of flexible magnetic sensors for magnetic nanomaterials,a controllable preparation method of C₆₀@Fe₃O₄superparamagnetic nanoparticles is proposed,which achieves uniform particle size,good dispersion and superparamagnetism.The composite materials were characterized using XRD,FTIR,TEM,XPS,EDS and other characterization methods.Subsequently,C₆₀@Fe₃O₄was used as a magnetically sensitive material,carbon nanotubes were used as conductive sensitive units,and a super-elastic SEBS rubber film was used as a substrate to prepare a flexible magnetic field sensor.The performance of the sensor was tested and analyzed,and the magnetic field was detected.On this basis,in order to further improve the performance of the sensor,the experimental materials and the structure of the sensor were improved.A flexible hexagonal mesh plane structure substrate was prepared by 3D printing,graphene was used as a conductive sensitive unit,an improved flexible magnetic field sensor was prapared.The performance of the improved sensor was tested,and the sensor's sensing mechanism was further studied by SEM,EDS and optical microscope characterization of the sensor.The specific results are as follows:(1)The preparation process of C₆₀@Fe₃O₄is simple,environmentally friendly,and the product's performance is excellent.TEM results show that C₆₀@Fe₃O₄has good dispersibility and uniform particle size.C₆₀particles are distributed on the surface of Fe₃O₄to form a coating structure and play a good protective role.X-ray diffraction,Fourier transform infrared spectroscopy and energy dispersive spectroscopy results further prove that the composition of nanomaterials are Fe₃O₄and C₆₀.The VSM hysteresis loop of the nanocomposite shows that the product exhibits good magnetic response performance and superparamagnetism.The saturation magnetization reaches 69.5 emu/mg.This indicates that C₆₀@F_e3O₄nanocomposites can be used to prepare flexible magnetic field sensors.(2)For C₆₀@Fe₃O₄&CNT-SEBS flexible magnetic field sensor,the sensor has high elasticity and high transparency.The I-V test shows that the sensor has good volt-ampere characteristics,and the resistance will not be affected by other electrical signals.The repeatability test and stability test show that the sensor has good stability and reliability.As the intensity of the magnetic field increases,the resistance of the sensor decreases,and the sensitivity is 0.021 T^-1.(3)For the improved 3D printed planar hexagonal mesh structure sensor,three sizes of sensors with side lengths of 5 mm,7 mm and 9 mm were prepared.The I-V test shows that the sensor has good ohmic characteristics.When the magnetic field is increased in both directions,the sensor shows a tendency to decrease in resistance.The sensitivities of the three sizes of sensors are 0.083T^-1,0.097T^-1and 0.066T^-1,respectively.In addition,the repeatability and stability experiments show that the repeatability and response speed of the sensor have been improved.SEM characterization results show that graphene and C₆₀@Fe₃O₄are uniformly distributed on the surface of the sensor.Using an optical microscope,it is found that the height distribution of the sensor under the magnetic field has changed significantly.On this basis,a sensing principle model is proposed.When the magnetic field increases,the magnetic particles tend to be arranged in chains,thereby enhancing the close contact between the graphene layers and enhancing the conductivity of the sensor.In summary,the flexible magnetic field sensor prepared with C₆₀@Fe₃O₄as the magnetic sensitive unit realizes the detection of the magnetic field,which lays the foundation for the research of flexible magnetic field detection.