Preparation And Properties Of TPU/CNTs Porous Membranebased Strain Sensor

Stretchable strain sensors have promising applications in many fields,including soft robotic skin,health monitoring,wearable electronics,and so on.Although many advances have been made in this field,there are still some bottlenecks for the strain sensors to be resolved,such as contradiction between low detection limit and wide strain response range,which hinder their practical application in various fields.Moreover,among the various characteristics of the stretchable strain sensor,low detection limit and wide induction range are the two most critical characteristics that determine its practical application.However,it is still a great challenge to achieve both ultralow detection limit and ultrawide sensing range at the same time,which often needs to make a tradeoff between them.Under this background,this paper prepared porous thermoplastic polyurethane(TPU)membrances by ultrasonication or solution casting technology,and then anchored carbon nanotubes(CNTs)onto the surfaces of porous TPU membrances,which disgined high-performance strain sensors.Attributed to the evolution of the hierarchically condutive pathway of CNTs layer under stretching-releasing,the TPU/CNTs porous membrance-based sensor possesses both ultralow detection limit and ultrawide sensing range.Specific research contents and conclusions are as follows:(1)We propose a simple route to design stretchable strain sensor with both ultralow detection limit and ultrawide sensing range by the combination of electrospun technique and ultrasonication anchoring technique.Specifically,a highly stretchable fibrous membrance is fabricated via electrospun technique and CNTs are then anchored onto the surface of TPU nanofibers assisted by ultrasonication.Subsequently,two Cu electrodes are assembled onto TPU/CNTs fibrous membrance to fabricate the strain sensor.Attributed to the multiscale evolution of the conductive network under stretching,the designed strain sensor possesses many outstanding merits,such as ultra-low detection limit(0.05%),ultrawide sensing range from 0.05% to 600%,fast response time of 75 ms,and excellent durability.Because of these outstanding merits,the TPU@CNTs fibrous membrance-based strain sensor can detect both the subtle strain change caused by sound of piano and the large strain change caused by the large-scale motions of joints.Moreover,it is found that TPU@CNTs fibrous membrancebased sensor makes a response to temperature and humility,which has great potential in temperature sensor and humility sensor.(2)Through the combination of solution casting technology and ultrasonic anchoring technology,we prepared an ultra-high tensile membrane wiht hierarchically porous and perforated structure and used it to design into strain sensor,which has ultra-low strain detection limit and ultra-wide sensing range.Firstly,a high ductility multistage porous TPU membrance is prepared by solution casting.Then,CNTs are anchored onto the surface of porous TPU film assisted by ultrasonication,and a high ductility multistage porous strain sensor is fabricated.Due to the evolution of the condutive CNT layer structure for microcrack structure to the fragment structure and the existence of the connection structure between the TPU holes,sensor exhibits many merits,including ultra-low detection limit(0.01%),ultra-wide strain sensing range(0.01%?900%),and excellent linear relationship between the resistance change rate and the strain in the sensing range.The strain sensor can accurately detect subtle strain changes caused by pulse pulsation and large strain changes caused by large-scale joint motion.In addition,it is found that TPU/CNTs sensor can not only detect the change of airflow at a distance of 30 cm,but also monitor the microexpression of human face and human movement.