Study On The Preparation,structure And Strain Sensing Properties Of Carbon Nanotubes/SEBS Elastomer Composites

In recent years,the strain sensor,the core component of wearable electronic equipment,has a broad application prospect in the fields of human motion/health monitoring,human-computer interaction,bionic robot,etc.,and has attracted more and more attention.Traditional strain sensors usually rely on rigid materials such as metals and semiconductors as electrodes,which generally have small strain measurement range and poor matching with human skin mechanics,so they cannot meet the development needs of flexible wearable devices.Based on the flexible polymer matrix,polymer based conductive nanocomposite electrodes are constructed,and flexible wearable strain sensors are constructed with these electrodes,which are easily attached to clothing or skin.Through the evolution of the network structure of conductive fillers in the stress-strain process,strain signals can be transformed into recognizable electrical signals.Therefore,it has important research value and application prospect.However,how to prepare polymer-based conductive nanocomposites and their flexible strain sensors with high elasticity,high conductivity and high cycle stability at low cost and high efficiency is still a challenge.In view of this,in this thesis,styrene-ethylene-butylene-styrene block copolymers(SEBS)are used as a flexible polymer substrate,and carbon nanotubes(CNTs)are used as conductive nanofillers.Superhydrophobic CNTs/SEBS composites and honeycombed CNTs/SEBS composites have been prepared by hot pressing and breath figure methods,respectively,and flexible strain sensors are assembled and their strain sensing properties are studied in details.The main contents of this thesis are as follows:1.The superhydrophobic CNTs/SEBS composites were prepared by hot pressing the original CNTs powder on the surface of SEBS films.The original CNTs powder is gradually embedded into the SEBS films which are heated to the viscous flow state under pressure.The different shrinkage of CNTs and SEBS during the cooling process makes the CNTs layer form a unique wrinkling structure on the surface of SEBS.The CNTs/SEBS composites exhibit excellent hydrophobic properties.The static water contact angle of the CNTs/SEBS composite film reaches161°,which still maintains stable superhydrophobic properties under various conditions.The flexible strain sensor based on superhydrophobic CNTs/SEBS composites exhibits an excellent strain sensing performance.The maximum strain monitoring range can reach 80%,and the response time is about 80 ms.The hysteresis effect of the flexible strain sensor is small,which therefore shows a high repeatability and dynamic durability.The flexible wearable strain sensor not only measures large deformation movement such as hand bending,but also monitors small deformation movement such as vocalization and pulse.Therefore,the superhydrophobic CNTs/SEBS composites and their flexible strain sensors have potential applications in wearable devices.2.The SEBS with honeycombed CNT structures on the surface has been prepared by dynamic breathing figure method,and then a stable dispersion of CNTs was sprayed on the honeycombed SEBS film to prepare the CNTs/SEBS composites with the honeycombed structure.The results show that temperature,concentration of SEBS solution and aeration time would tailor the pore structure of honeycombed SEBS.The SEBS with the honeycombed structure has good conductivity(?_v=1.14Wm)after spraying the CNTs.The flexible strain sensor based on the honeycombed CNTs/SEBS composite shows a large strain measurement range(120%),and the resistance linear response range can be divided into three regions,which consist of 0-13%,13-65%and 65-120%,respectively.In these three regions,the sensitivity coefficient of gauge factor(GF)reaches 1.51,3.01 and 1.74,respectively.In addition,the strain sensor has fast response time(82 ms)and excellent dynamic durability.After 1000 tensile/recovery cycles,the resistance response hardly changes.Therefore,the honeycombed CNTs/SEBS composites and their flexible strain sensors have potential applications in the field of wearable devices.