Research On Flexible Electromagnetic Devices Based On High-Performance Metal Materials

Human society has undergone significant transformations due to the rapid advancement of electronic devices.As electronic products continue to undergo updates and iterations,individuals are placing increasingly higher demands on their capabilities.In the present era,conventional rigid electromagnetic devices are unable to cater to diverse usage scenarios,leading to the emergence and growing market share of flexible electromagnetic devices.Compared to rigid devices,flexible counterparts exhibit superior properties such as bendability,stretchability,and compressibility,often boasting lighter weight and enhanced portability.The adaptability of flexible electromagnetic devices to complex surfaces enables their application in various fields.Notably,they have garnered increasing utilization rates in areas like smart wear,health monitoring,energy storage,and electromagnetic shielding.The preparation of flexible electromagnetic devices generally involves the selection of suitable flexible substrate materials and conductive materials,followed by their appropriate assembly.The selection of the appropriate substrate material,conductive material,and assembly method in accordance with specific usage requirements has been the focal point of research in the field of flexible electromagnetic devices.Nevertheless,numerous challenges persist in the preparation strategy of such devices across multiple domains.These challenges include the inability to simultaneously meet all crucial requirements and the lack of large-scale,high-efficiency,and cost-effective preparation methods.Consequently,many products remain confined to laboratory settings,impeding their widespread adoption.This study focuses on three practical application fields of flexible electromagnetic devices:electromagnetic shielding,brain-computer interface electrodes,and electrocardiogram acquisition electrodes.The research will encompass essential characterization and testing procedures.Following each phase of work,a demonstration will be conducted to simulate real-world environments,aiming to address practical challenges.Our proposals for each application field will prioritize functionality,safety,as well as the feasibility of cost-effective,large-scale,and efficient production of flexible devices.The specific work content is outlined as follows:1.We designed a conductive mesh and checked its electromagnetic shielding performance by electromagnetic wave simulation software.Using the electromagnetic shielding structure and parameters determined by simulation,we prepared a flexible electromagnetic shielding fabric by a simple immersion method using silver nanowires,polyvinyl butyral ethanol solution,and a flexible fabric substrate.In the frequency range from 5 GHz to 18 GHz,the electromagnetic shielding cloth with a thickness of 1.4 mm achieved an electromagnetic shielding effectiveness of 59 dB,exceeding the requirements for commercial applications.Due to the low density(56 mg/cm3)of the electromagnetic shielding cloth,the special shielding effectiveness of this material reaches 1053 dB·m3/g.At the same time,we found that the introduction of PVB greatly enhanced the waterproof and oxidation resistance of the electromagnetic shielding fabric.In the final practical demonstration,we found that the electromagnetic wave detector cannot detect the radio signal from the mobile phone in the jacket lined with electromagnetic shielding fabric.In addition,the electromagnetic shielding cloth can be efficiently mass-produced at low cost for commercial applications.2.We fabricated semi-dry ECG electrodes with extremely low impedance and high stability by metallizing polyvinyl alcohol hydrogel on the surface of silver nanowires.When using the electrode,the electrolyte in the polyvinyl alcohol hydrogel is continuously and slowly released in the skin-electrode interface and the stratum corneum,effectively reducing the impedance of the interface and the stratum corneum,and minimizing the transmission of the ECG signal attenuation in.The electrodes can continuously acquire high-quality ECG signals within 24 hours.In addition,the electrodes can also collect signals during the subjects’ movements.This semi-dry electrode can be mass-produced at low cost,and has broad application prospects in scenarios that require long-term accurate ECG monitoring.3.We developed a semi-dry BCI electrode assembled from silver nanowire metallized polyvinyl alcohol hydrogel and silver nanowire metallized melamine sponge,which can be used for long-term EEG signal acquisition and application of brain-computer interface.Thanks to the water storage capacity of the hydrogel,the electrolyte solution can be continuously released to the scalp-electrode interface during use.The electrolyte solution can penetrate into the stratum corneum and reduce the scalp electrode impedance to 10 kΩ-15 kΩ.The flexibility makes the electrodes mechanically stable,increases wearing comfort and reduces the thickness of the air layer in the scalp-electrode interface to reduce interface impedance.A three-hour long-term BCI application based on the motor visual evoked potential paradigm demonstrated that the new electrodes had roughly the same recognition accuracy as the conventional electrodes in the first hour,and the new electrodes were accurate in the third hour of testing The accuracy remains high,while the accuracy of traditional wet electrodes will be significantly reduced.In addition,the brain-computer interface system based on the new electrodes can maintain low contact impedance for 10 hours,greatly improving the capabilities of braincomputer interface technology.In addition,we have also confirmed that the electrode has no biosafety risk through animal experiments.