Preparation Of Self-healing Polyurethane And Its Application In Flexible Sensor

With the rapid development of information technology and artificial intelligence,especially with the arrival of 5G era,it is an irresistible trend to realize the Internet of everything,and people's demand for flexible wearable electronic devices is also increasing.As the key device of human-machine interaction in wearable devices,flexible mechanical sensor has attracted extensive attention.Although the common flexible mechanical sensor has good sensitivity and good stretchability,it is often subjected to mechanical deformation in practical application,prone to fatigue damage or accidental damage,which not only shortens the service life of the device,but also greatly reduces the operation reliability of the device.Recently,introducing self-healing materials into mechanical sensors become one of the hot topics,which is expected to solve this problem.However,most of the current researches on self-healing mechanical sensors use hydrogel as the substrate,which has low strength and is not suitable for long-term use.In this work,self-healing polyurethane have been prepared based on reversible covalent bonds,and then the polymer were used as substrate,combined with the nanomaterials?such as silver nanowires,graphene,carbon nanotubes?or conductive polymer?such as polypyrrole?,to prepare self-healing sensors through certain structure design.The as-prepared sensors not only have good sensing performance,but also have strong self-healing performance.The specific research content is as follows:1.A self-healing polyurethane based on Diels-Alder reversible reaction?PUDA?was synthesized by a two-step process.Based on the PUDA,a capacitive pressure sensor was fabricated through sandwich structure design.The PUDA was composited with silver nanowire?AgNWs?as electrode.To improve the sensitivity of the sensor,a homemade template was used to replicate the wavy microstructure onto one of the electrodes,and graphene was filled into the dielectric layer film to improve the dielectric constant of the dielectric layer.Finally,the sensitivity of the flexible pressure sensor was up to 1.9 kPa^-1when the graphene content was 1.5 wt%,and it has good cyclic stability.After mechanical damage,the sensitivity can be restored over 70%by heating at 120? for 10 min.2.A self-healing polyurethane based on disulfide exchange reaction?PUSS?was synthesized by a two-step process.Based on the PUSS,three-dimensional porous structure was formed by salt template method,and a stretchable and compressible pressure/strain sensor was prepared by in-situ polymerization of polypyrrole on the surface of porous structure.As a strain sensor,its gauge factor?GF?is up to 8.98,response time is within 100ms,and the minimum detection limit is 0.1%.As a pressure sensor,its sensitivity?S?is up to6.47 kpa^-1,response time is within 100 ms,and the minimum detection limit is about 50 Pa.Both of them have good cyclic stability.Most importantly,the mechanical and sensing properties of the sensor can be restored after being completely cut off.