Design Of Biomass-Based Janus Nanocomposites And Its Application In Self-Healing Hydrogel Flexible Sensors

Nanocomposite hydrogels prepared by surface modification of biomass nanomaterials can improve the poor mechanical properties and easy fracture of traditional hydrogels,so that they can be widely used in wearable flexible sensing and human movement monitoring.Janus nanomaterials are defined as asymmetric nanocomposites with two or more different chemical structures or properties on their surfaces.By assigning different functional groups to different surface regions of the same material,the disadvantages of traditional nanomaterials with single performance can be effectively solved.This allows for synergistic improvements in the mechanical,self-healing,and electrical properties of hydrogels,thus expanding their applications in wearable flexible sensing.This paper is based on the design and preparation of biomass-based Janus nanocomposites using different biomass materials such as cellulose nanocrystals,polydopamine,and gelatin.By combining nanomaterials with hydrogel substrates,a self-healing nanocomposite hydrogel with excellent mechanical properties,self-healing performance,and conductivity was constructed to develop a flexible hydrogel sensor.The study examines the mechanism by which different Janus nanomaterials affect the mechanical properties,self-repairing performance,and electrical conductivity of hydrogels,achieving synergistic improvements in all performance aspects.This has led to the development of a highly sensitive,wide detection range,and fast response wearable flexible sensor,which was applied in real-time monitoring of human motion.The paper consists of three parts:1.The preparation of cellulose nanocrystal-based Janus nanocomposites and their application in self-healing hydrogel flexible sensors.The poor mechanical properties and low toughness of traditional hydrogels severely limit their application.The introduction of biomass nanomaterials has opened up new avenues for the modification of hydrogels.Cellulose nanocrystals（CNCs）are rich in hydroxyl groups on their surface,providing multiple reaction sites for the preparation of novel functional nanomaterials as well as traditional hydrogels.Janus-type CNCs materials were prepared using Pickering emulsion templating method.By asymmetrically grafting polypyrrole（PPy）and polydopamine（PDA）onto different sides of the CNCs（Janus CNCs-PPy/PDA（JCNs））,asymmetric functionalization and modification of Janus nanorods were achieved.JCNs were then embedded in hydrogels to successfully and effectively design functional JCNs/polyacrylic acid（PAA）nanocomposite hydrogels.Under the synergistic effect of multiple hydrogen bonds and metal coordination,JCNs/PAA hydrogels exhibited excellent mechanical properties（3.50 MPa）,self-healing efficiency（87.2%）,biocompatibility and conductivity.The flexible sensor applied in human motion and health monitoring demonstrated high sensitivity（GF=9.9）.Therefore,JCNs/PAA nanocomposite hydrogels can be applied to the design and development of flexible wearable devices.2.Preparation of SiO₂/PDA-based Janus nanocomposites and their application in self-healing hydrogel flexible sensors.Janus-type biomaterial nanocomposites（JSNs）were prepared by modifying the surface of SiO₂ biomaterial with dopamine（DA）coating and gold nanoparticles（Au NPs）using mussel-inspired chemistry and oxidation-reduction of metal nanoparticles.Janus-type SiO₂ nanoparticles were implanted into a PAA-based hydrogel polymer network to construct JSNs/PAA self-healing nanocomposite hydrogels.Under the action of multiple hydrogen bonds and metal coordination,the structure of the nanocomposite hydrogel became more compact,and the mechanical,self-healing,and conductive properties were significantly improved.The resulting JSNs/PAA hydrogel had a mechanical strength of2.18 MPa,a strain of 664.02%,a self-healing efficiency of 91.3%,and exhibited good fatigue resistance.This flexible sensor also has good development prospects in wearable electronic devices for sensitive detection of human movement and health status（GF=1.59）.3.Preparation of gelatin-based Janus nanocomposites and their application in self-healing hydrogel flexible sensors.Gelatine nanospheres were crosslinked by a two-step desolvent method with Genipine.Janus gelatine nanospheres（JGNs）coated with polydiallyl dimethyl ammonium chloride（PDDA）and tannic acid（TA）were prepared by Pickering emulsion template method,and were successfully applied in the development of nanocomposite hydrogels.And a flexible sensor with outstanding advantages was built.Through the synergistic effect of metal coordination and hydrogen bonding,the nanocomposite hydrogel exhibited excellent mechanical properties（strain=616%,stress=2.85 MPa）and self-healing properties（self-healing efficiency up to 90.9%）.The developed JGNs/PAA hydrogel sensor had high sensitivity（GF=3.69）and a fast response time（280 ms）.In human motion monitoring,the hydrogel sensor was able to detect small deformations such as mouth opening and typing,as well as large deformations such as joint bending.Therefore,the construction of self-healing hydrogel flexible sensors has important applications in the field of human motion monitoring.