Study Of A Kirigami-Inspired Paper-Based Flexible Sensor For Orofacial Monitoring

In the past few years,wearable electronics have gained popularity,and wearable flexible sensors have emerged as a promising technology in the domains of personalized medicine and human-computer interaction.Additionally,they offer new opportunities for real-time dynamic monitoring of oral and maxillofacial muscle groups,as well as quantitative occlusal indications.Despite the continuous reports of flexible piezoresistive sensors with high sensitivity,their complex microstructure construction process,microstructure fragility leading to sensing failure,high preparation cost,and environmental burden from difficult recycling or degradation have hindered their application in clinical settings.However,taking inspiration from the traditional art of kirigami,flexible pressure sensors with high sensitivity were successfully prepared through laser-patterned etching of a paper base and compounding it with graphene ink as follows:Objective:The aim of this paper is to prepare a flexible paper-based sensor with a kirigami structure inspired by the art of kirigami.Our goal is to enhance the performance of the sensor through the kirigami structure,improving both its ductility and sensitivity.This will allow it to better conform to the skin and occlusal surface,and broaden its application in clinical settings.Methods:1.The Finite Element Method（FEM）engineering software was used to model and simulate the effects of different configurations of the kirigami structure on the strain capacity and potential field distribution of the paper-based sensor devices,and to predict the optimal kirigami structure design for flexible paper-based sensors.2.The kirigami structure was designed by combining the results of Finite Element Analysis（FEA）,and the kirigami structure graphene/Xuan paper was obtained by impregnation-freeze-drying method and laser cutting.Based on this,kirigami structure graphene paper-based sensors were prepared by layer-by-layer assembly method.3.Atomic Force Microscope（AFM）and Scanning Electron Microscope（SEM）were used to characterize the microscopic morphology of paper-based graphene sensors with kirigami structure.4.The test platform was constructed by a universal mechanics experiment machine and a digital multimeter,and the strain capacity,pressure sensing capacity,Relative Humidity（RH）sensing capacity,and durability performance of the paper-based graphene sensor with kirigami structure were tested.The sensing principle was also analyzed with the microscopic characterization results.5.Kirigami structured graphene paper-based sensors were attached to the surface of the skin in different parts of the human body to explore the application potential of the sensors in detecting human physiological signals and motion signal monitoring.6 An array of occlusal sensors was made to detect dental occlusal highs by integrating kirigami structured graphene paper-based sensors on a flexible substrate to explore its potential for occlusal detection.Results:1.Different configurations of kirigami structures have a significant effect on the strain capacity and potential field of the paper-based sensors.The kirigami structure group showed up to 16 times higher strain rate than the structureless group under the same tensile force.Based on the FEA results,the optimal kirigami configuration for the oromaxillofacial muscle pressure sensor was preferentially selected.2.Based on the optimal kirigami conformation,kirigami structure graphene/Xuan paper was successfully prepared,and based on this,multifunctional kirigami structure graphene paper-based sensors were prepared.3.The successful composite of graphene/Xuan paper was demonstrated by AFM,SEM,and other characterization means,and the microstructure was observed,which laid the foundation for the subsequent analysis of sensing principles.4.Benefiting from the structural design of the graphene paper-based sensor,the sensor has the advantages of excellent stability（more than 23,000 load-release cycles）,high pressure sensitivity(37.61 k Pa^-1 at 28 Pa),fast response（compression response time less than 60 ms）,and also high linear output humidity sensing（R²=0.93285）.The sensing principle is explained in conjunction with the microscopic morphological characterization results.5.The kirigami structured graphene paper-based sensor was attached to human skin and successfully monitored human physiological signals（e.g.,arterial pulsation,respiration）and successfully detected facial expressions（e.g.,frown）and human joint movements（e.g.,elbow,wrist,and finger joint movements and head nodding movements）.6.The occlusion sensing array was successfully prepared,and the early contact and distribution detection of multiple occlusion high points were completed on the occlusion model.Conclusion:The application of the kirigami structure has proven to effectively enhance the strain capacity and sensitivity of paper-based sensors.In this research,we successfully prepared kirigami structure graphene paper-based sensors that can detect motion and monitor physiological signals in different body parts.This sensor has the potential to provide quantifiable health data monitoring for patients undergoing muscle rehabilitation therapy and can detect environmental relative humidity.Additionally,the occlusal sensing array was able to detect multiple occlusal high points in an occlusal model,showing promise for providing a new research idea and method for dental clinical occlusion examination.The structural design idea of this sensor will promote the development of flexible electronic devices in the field of intelligent medicine,providing a new idea and method to realize the intelligence and portability of medical technology.