Preparation And Investigation Of Sensing Performance Of TPU/CNTs Multilayer Alternating Layered Foam

With the continuous advancement and development of flexible electronics technology,flexible strain sensors have become a highly focused research area.Generally,in order to achieve a wide detection range,flexible strain sensors require a higher loading of conductive fillers in elastic conductive polymer composites（ECPC）.However,this can cause a decrease in the mechanical performance of the sensor and lower sensitivity,making it unsuitable for human detection needs.Therefore,how to achieve a wide detection range and high sensitivity strain sensor with a low loading of conductive fillers has become a key issue in current research.To address these issues,this paper proposes a flexible strain sensor with a layered and bimodal porous structure,which can achieve high sensitivity and a wide sensing range at a low ratio of conductive fillers.This paper focuses on the preparation and sensing performance of the sensor,with specific research topics outlined below.（1）Given that the layered foam of polymer foam is prone to stratification,and the preparation process has a significant impact on the foam morphology.Thus,this chapter prepared a layered foam of a single thermoplastic polyurethane（TPU）and studied in detail the effect of the stacking hot pressing and foaming process parameters on the foam structure,providing a foundation for subsequent experiments.The results show that the optimal stacking hot pressing process parameters are 170℃and 10 MPa.The TPU layered foam diameter increases and the foam density decreases with increasing foaming temperature.The foam diameter decreases and the foam density increases with increasing foaming pressure.Layered foam with a multilayer and continuous porous structure(FTPU-L₂₀ T_YP₁₀)was successfully prepared.（2）Based on the previous research,this chapter added carbon nanotubes（CNTs）to TPU and prepared a TPU/CNTs flexible strain sensor with an alternating layered and bimodal porous structure.The effect of the number of layers and foam structure on the sensitivity of the sensor was studied in detail,and its sensing performance and application in human detection were characterized.The experimental results show that the construction of interlayers and bimodal porous structures effectively improved the sensitivity of the sensor and significantly reduced the content of conductive fillers.Among them,the FTPU-C3-L₁₀T₈₀P₁₀ sensor had the best sensitivity（101）and had excellent tensile properties,a wide sensing range（150%）,a fast response time（<200 ms）,and excellent stability（1000 cycles,30%strain）.Additionally,the sensor is also suitable for a wide range of human motion detection,such as facial expressions and small arm muscle contractions.（3）To further improve the sensitivity of the sensor,this chapter added carbon black（CB）to TPU/CNTs composite materials and prepared a TPU/CNTs/CB strain sensor with an alternating layered foam structure.The effect of the ratio of CNTs and CB content on the sensitivity of the sensor was studied,and its sensing performance and application in human detection were characterized.The research results show that the synergistic effect of CB and CNTs further improved the sensitivity of the flexible strain sensor.Among them,the FTPU-CNT₁/CB₂ sensor had the best sensitivity（157）,a fast response time（175 ms）,excellent tensile properties,and a wide sensing range（150%）.The sensor is suitable for a wide range of human motion detection and shows potential in health monitoring applications.