Stretchable Mechanoluminescent And Conductive Fibers With Core-sheath Structure And Their Applications

Nowadays,more and more products are developing towards flexible materials.The development of flexible sensing devices has greatly promoted the application of wearable products and smart clothing.Compared with traditional sensing devices,flexible sensing devices can better fit the human body and realize sensing because of their soft and flexible characteristics.At present,a large number of organic conductive materials have been discovered,such as organic conductive materials and doping conductive materials in organic insulating materials to construct conductive networks to achieve conductivity.Although these conductive materials can meet the requirements of flexible conduction,and stress sensing is generally realized through the change of resistance or capacitance,their functions are relatively single.Mechanoluminescent materials are materials that can realize visual stress sensing,that is,they show different luminescent properties with the change of external force.Up to now,there are few studies on the combination of the two.It is the future development trend in this field to realize flexible stress sensing by superimposing resistive and luminous sensing characteristics under stress state.This dual-mode sensing has considerable development potential in smart wearable products,motor skill detection and human health.In this thesis,the preparation of flexible conductive mechanoluminescent materials and their applications in flexible electronic devices are explored.The main research contents are as follows:（1）First of all,sodium alginate gel was used as matrix material,and flake graphene and one-dimensional carbon nanotubes were used as conductive fillers to prevent graphene agglomeration and improve conductivity.Carbon nanotubes and graphene were uniformly dispersed into sodium alginate gel by ultrasonic dispersion and repeated stirring to prepare conductive layer.The relationship between strain and electrical resistance was investigated.The conductive fibers with conductive filler content of5wt%,10wt%,20wt%,30wt%and 40wt%were prepared,and the elongation at break of the fibers was up to 76%.Zn S:Mn²⁺mechanoluminescent powder with better mechanoluminescent effect was prepared.In order to make better luminescence effect,Zn S microspheres were prepared by coprecipitation method for firing mechanoluminescent powder.Mechanoluminescent powder can be prepared by molten salt oxygen isolation method in aerobic environment,and the mechanoluminescent effect can be achieved by uniformly mixing the mechanoluminescent powder prepared by this method into the substrate.A mechanoluminescent conductive fiber with core-shell structure is designed,which can realize dual-mode stress sensing.The mechanoluminescent structure adopted in the outer layer of the fiber can realize non-contact optical measurement,while the internal core structure is a conductive structure,which can measure the strain through the change of resistance.（2）In order to improve the intensity of mechanoluminescent,Zn S:Mn²⁺and Ca Zn SO:Mn²⁺mechanoluminescent powders with different Mn²⁺doping concentration were prepared by high temperature solid state reaction in vacuum,and the luminescence intensity was enhanced in different degrees.The luminescence intensity of Zn S mechanoluminescent powders with 0.5%Mn²⁺doping was 520%of that of the mechanoluminescent powders prepared by molten salt oxygen isolation method.And by controlling the content of sodium alginate,the fiber elongation at break can reach 160%.When the fiber is pasted on the surface of the measured point or woven on the fabric,with the deformation of the structure,the strain generated at the pasting point will change the resistance of the conductive fiber due to piezoresistive effect,and an electrical signal will be generated and output by the lead-out line;The outer layer produces different intensity fluorescence due to different strains,so as to realize the real-time stress monitoring effect.