Simulation And Experimental Study On Performance Optimization Of Flexible Strain Sensor Based On Liquid Metal

Sensors are the most important part of modern information technology.With the development of electronic technology and material science,people have put forward new requirements for sensors.They hope that sensors can be flexible,stretchable and miniaturized to adapt to the complex environment and signal measurement on irregular surfaces.In recent years,researchers have developed a large number of flexible strain sensors adapted to different application scenarios through materials,sensing mechanism,structural design and other aspects.Compared with the long research on material development,it is more intuitive and effective to improve the performance of the sensors through structural design and has the significance of engineering practice.In this paper,from the perspective of finite element structural analysis,a flexible strain sensor finite element model is established,and the flexible strain sensor is structurally optimized.Based on the analysis,a flexible strain sensor with low hysteresis and excellent performance is designed based on the MEMS process.Finally,experimental design and further characterization of the designed sensor model were carried out through experiments.The main work content and conclusions are:(1)Compared with a variety of superelastic models,the Yeoh model was selected as the material constitutive model under the condition of limited experimental equipment,and the stress-strain relationship of the Yeoh model was derived,and Mcalibration software developed by Bergstrom et al.was used to fit the Bergstrom-Boyce model with Yeoh model as part of elastic network(2)The model of single-channel flexible strain sensor is established,and the influence of channel aspect ratio(1:1,1:2 and 1:5)on the mechanical properties of the sensor under the action of 100%and 150%final tensile strain is analyzed,indicating that the influence of aspect ratio on the performance of the sensor can be ignored.According to the requirement of the characteristics combined with the thickness of the film,a 1:5 aspect ratio design is adopted,and the flexible strain sensor model with channel side curvatures of 0°(rectangular channel),70°and 180°is further carried out.The stress distribution,stress-strain hysteresis,resistance hysteresis and energy loss of the model during the tensile process are studied.It is found that the stress-strain hysteresis performance of the flexible strain sensor is improved with the increase of the sidewall curvature,and the hysteresis of the resistance It has also been improved,especially for flexible sensors with a curvature of 180°,and the hysteresis is improved compared to the other two models.At the same time,the energy loss also decreases as the curvature increases.(3)The effects of three spin coating speeds and three exposure doses on the thickness and width of the microchannel mould were investigated.The maximum spin speed corresponding to the 150 um thickness required for the test and the 375 um line width and the exposure doses were determined to be 1940 rpm and 235 mJ/cm~2,respectively.Three flexible strain sensors with microchannels were prepared using the Ecoflex semi-curing process.(4)Using the electronic universal testing machine to verify the mechanical properties of three flexible strain sensors with microchannels,comparing the stress-strain curves of the three channels and the hysteretic behavior,it is found that with the increase of the inner side wall curvature the hysteresis also increases,indicating the rationality of the aforementioned model.Furthermore,the static performance analysis of the sensor is further combined with the digital source meter.It is found that the linearity is slightly improved with the increase of the sidewall curvature.The linearity is between 5.8%and 8.5%,and the influence on GF can be neglected.As the curvature of the sidewall increases,the hysteresis is greatly improved.The hysteresis error of the flexible strain sensor decreases from 1.7%to 0.13%with the increase of the arc.The above results show that the structural design based on finite element analysis effectively improves the performance of the flexible strain sensor.