A Research Of Electromechanical Coupling Effects In Flexible Mechanical Sensors

Flexible electronics have developed rapidly in recent years and have broad market prospects in the future.As an important part of flexible electronic systems,flexible mechanical sensors have aroused high research enthusiasm,and have broad application prospects in the fields of personalized medical care,motion detection,and humancomputer interaction.In recent years,flexible mechanical sensors have made significant progress,in performance,integration,and multifunctional requirements.Currently,many researchers have worked on the flexible mechanical sensors by two design schemes:medication of active materials and structural design on the flexible substrate.As a conductive device,a flexible mechanical sensor can convert external physical stimuli into measurable electrical signals.Therefore,the electromechanical coupling effect in the signal conversion process is the key to affecting the sensing performances.Accordingly,this dissertation is focused on the electromechanical coupling effect of flexible mechanical sensors and proposed several devices schemes to adapt to the complex application environment.In addition,based on the effect of electromechanical coupling in different mechanical sensors,several kinds of flexible mechanical sensors with tunable properties were designed and demonstrated,and the application of flexible mechanical sensors in different complex and changeable scenarios was discussed.The main research contents are presented as follows:1.The patterning design was introduced into the laser-induced graphene,and the reduced graphene oxide films were prepared by Joule heating.It is proved that the strain distribution of the graphene film was redistributed with pattern design.Due to the redistribution of the interface stress between the graphene film and the flexible substrate,the crack distribution and diffusion pattern of the graphene film changes accordingly,which in turn affects the electromechanical properties of the graphene film.The flexible strain sensor was fabricated based on the patterned r GO film and exhibited various sensing performances.Through the comparison of the sensing performance of flexible strain sensors with three different feature structure patterns,the modulable effect of patterning design on the electrical properties of the sensor was confirmed.In addition,the flexible strain sensor was employed to monitor the muscle beating around eyelids and further realized the pattern recognition function of the fatigue state.2.An efficient strategy to construct an ultra-highly sensitive,flexible pressure sensor by rebuilding the microstructures in laser-induced graphene.the laser-induced graphene was prepared with spinosum microstructure,and the intercalated structures between microspheres and graphene flakes were formed by introducing a magnetic field.The synergy effect of surface spinosum microstructure and ordered magnetic microspheres contributes to the superior piezoresistive properties of graphene composites.Under the synergistic effect of the surface morphology and internal structure of the materials,the pressure sensor possesses excellent sensing properties such as high sensitivity and wide sensing range.In addition,these superior sensing properties trigger applications in healthcare monitoring and spiral pressure spatial distribution in conjunction with mechanical flexibility and robustness3.By introducing an auxetic metamaterial with a negative Poisson's ratio effect to control the deformation behavior of the microfluidic,the electrical response properties of the microfluidic strain sensor are effectively modulated.The limitation of the directional coupling effect of a microfluidic strain sensor was broken through the structural design of metamaterials,and omnidirectionally sensitive and directionally insensitive microfluidic strain sensors are prepared respectively.In addition,the microfluidic strain sensor with insensitive performances in a specific direction is applied to the precise tactile detection of the human skin,which effectively shields the interference of the tactile signal by other movements such as bending.4.A flexible reconfigurable strain sensor based on a heterogeneous substrate was present and demonstrated.The heterogeneous substrate based on the strain-concentrated structure was designed.The heterogeneity was controlled by introducing phase change material.A flexible heterogeneous substrate with reversible and controllable mechanical properties was controlled by an external electrical system.The reconfigurable flexible strain sensor with real-time customizable sensing performances is demonstrated,and the response properties of the strain sensor change in real-time with the strain redistribution.The research results are expected to improve the understanding of the electromechanical coupling effect of flexible mechanical sensors and enrich the device design strategy of application-oriented flexible mechanical sensors.