Research On High Sensitivity Flexible Strain Sensor Based On Mechanical Metamaterials

Flexible strain sensors are widely used in medical,human health monitoring,robotics and other wearable electronic devices,and have broad commercial application prospects,so they have been extensively studied in recent years.Sensitivity is one of the key indicators of the sensor.The current research reports mainly improve the sensitivity of the flexible strain sensor by optimizing the sensitive material,the substrate material and the substrate surface structure,but each has its limitations,which limits the further improvement of the sensor sensitivity.In this paper,through the study of negative Poisson's ratio mechanical metamaterials on elastic substrates,two types of flexible strain sensor structures,resistive and capacitive,are designed with the sensitive structure layer along with the elastic substrate extending longitudinally and transversely at the same time,so that the two types of sensors have higher sensitivity.The gauge factor is up to2554.48 and the linearity is 0.9917 in the strain range of 8-20%.At the same time,the method of mechanical metamaterial elastic substrate proposed in this paper is proved to have universal validity.The main research contents are as follows:(1)Combining the theoretical model of mechanical metamaterials,the finite element simulation of perforated plate structure and reentrant structure with mechanical metamaterial characteristics is performed,and the influence regulations and characteristics of different structural size parameters on the longitudinal/transverse displacement deformation of the two structures are analyzed.(2)Based on the above-mentioned theory and simulation optimization analysis,the resistive flexible strain sensor based on the improved perforated plate structure and the capacitive flexible strain sensor based on the reentrant structure and their manufacturing processes are designed,and the working mechanism of the sensor is studied respectively.(3)Comprehensive performance tests on two types of flexible strain sensors are researched.First,for the resistive flexible strain sensor,the effects of carbon-based zero-dimensional(carbon black),one-dimensional(carbon nanotube)and two-dimensional(graphene)materials as sensitive materials on the sensor's performance are studied.It also compares the influence of perforated plate structure substrate on sensor performance.Second,for capacitive flexible strain sensors,the influence of the presence or absence of reentrant structure substrate on sensor performance is analyzed and compared.(4)The application performance of the resistive flexible strain sensor in different scenarios is tested,which includes large-strain human limb joint motion detection,small-strain micro-expression detection,word syllable detection,carotid artery detection and other application scenarios test.In summary,two kinds of mechanical metamaterial structures are simulated and analyzed in this paper,and the optimal structural parameters are selected to produce the sensor.The sensitivity,linearity are tested,and the performance of sensors with different materials and structures is analyzed and compared,showing that the proposed scheme has excellent comprehensive performance.Finally,the performance of human wearable application is demonstrated,which shows that the sensor designed in this paper has potential application value in human motion monitoring,medical and health monitoring,intelligent wearable electronic devices and flexible robots.