Investigation On Construction And Performance Of Self-Healing Polyurethane Based Artificial Skin

Artificial skin(A-skin)is of great significance to the development of flexible bionic mechanosensation devices,which can be widely used in the fields of humanoid robots,artificial limbs,advanced medical equipment.Most A-skins are composed of polymer materials with weak resistance of mechanical damage and poor degradability,which significantly reduces the service robustness and environmental compatibility of A-skin.Therefore,it is urgent to improve the robustness during service and reduce the environmental cost of disposal for A-skins.Besides,the current A-skin has low mechanosensation accuracy and short continuous working time,which makes it difficult to meet broad demand for high performance and intelligence of wearable devices.Thus,there is an urgent need to develop A-skin with high precision sensing capability,and the equipment can work for a long time without external power supply.Based on this,this dissertation focuses on the robustness,environmental compatibility and mechanosensation capability of A-skin.By optimizing the mechanical properties,self-healing ability,degradability and surface activity of the self-healing polyurethane,the A-skin has high robustness and excellent environmental compatibility.The electrical conductivity of polyurethane was regulated by molecular chain design and conductive material doping,and the conductive polymer was used as electrode and resistance-switching layer of A-skin.Via the triboelectric-electrostatic induction effect,the A-skins have the self-powered mechanosensation capability,which can work continuously without external energy supply.Moreover,the electrochemical doping mechanism is used to store and process mechanosensation information,which greatly improves the sensing accuracy of A-skin.The specific research content is as follows:Three kinds of self-healing polyurethane elastomer were prepared by molecular structure and component design.A self-healing polyurethane elastomer(SPE)with excellent stretchability was prepared by regulating the ratio of hard and soft segments.It is proved that there are a large number of dynamic reversible hydrogen bonds and disulfide bonds in the SPE matrix,which can reconnect the broken molecular chains and achieve self-healing.The SPE film have 12 MPa fracture stress,700%fracture strain,32.8 MJ/m3 toughness,and the self-healing ability of surface scratch within 24 hours.Degradable self-healing polyurethane elastomer(DSPE)were prepared from synergistic soft-hard segments design.The mechanism on improving mechanical properties,self-healing ability and degradability of DSPE through the regulation of molecular structure and component was revealed.After 30 days of degradation,the mass loss rate of DSPE film was 25%,and there was no cytotoxicity.The fracture stress and strain of DSPE film are 23 MPa and 890%,and the toughness is up to 81 MJ/m3.After fracture,the DSPE film can be self-healed within 7 hours,and the healing efficiency is more than 90%.A waterborne self-healing polyurethane elastomer(WSPE)with surface active function was prepared by introducing polyether block polymer as soft segment.The WSPE can reduce the contact Angle between water and silicon wafer to 34.42°,and can self-heal surface scratches in 2 hours.Three kinds of self-healing conductive polyurethane elastomer were prepared by carbon black,ionic liquid and PEDOT:PSS doping respectively.Self-healing conductive elastomer(SCE)were prepared by doping carbon black in the SPE matrix.The influence of carbon black on the mechanical properties,electrical conductivity and self-healing ability of SCE was revealed.The SCE have 2 KΩresistance,350%elongation at break,4.5 MPa Young’s modulus and>70%self-healing efficiency at room temperature.Ionic gel(IG)was prepared by doping ionic liquid in DSPE.By controlling the molecular weight and component ratio of ionic liquid,the IG has excellent electrical conductivity and high toughness.Its resistance is 2 MΩ,fracture strain is up to 1400%,fracture stress is 10 MPa,and toughness is up to 50 MJ/m3.The self-healing resistance-switch elastomer(SRE)was prepared by blending WSPE with PEDOT:PSS.The influence of PEDOT:PSS content on the conductivity and self-healing ability for SRE is revealed to enable SRE have 20 KΩ resistance,50%stretchability and self-healing ability of conductivity.Based on the developed SPE and SCE,a fully organic homogenous A-skin is designed and constructed,which has a highly robust self-powered mechanosensation capability.The A-skin can realize stable pressure sensing under 50%tensile deformation,and its stretchability and mechanosensation capability can be restored with over 90%recovery efficiency after self-healing.Green highly robust A-skin was constructed by employing DSPE and IG.The device can withstand 50%cyclic stretching with same mechanosensation capabiltiy,resist notch tear over 200%tensile deformation,and fully restorable stretchability and mechanosensation capability after self-healing 7 hours.Moreover,the whole device can be degraded in water.An organic electrochemical neuromorphic devices was constructed by using SRE and IG.The regulation of the doping state for SRE and the composition for IG on the resistance-switching characteristics of neuromorphic device was systematically studied.The high-precision mechanosensing A-skin(HPMA-skin)was constructed by coupling the effects of triboelectric-electrostatic induction and electrochemical doping.Compared with the triboelectric A-skin,the mechanosensation accuracy of the HMPA-skin is greatly improved,and it has high service robustness and transient characteristics.This study will greatly promote the practical application of self-healing polyurethane materials and high-performance artificial skin in the fields of humanoid robot,artificial limb,advanced medical equipments.