Study On Preparation And Property Of Graphene Oxide-based Hydrogel

Smart wearable electronics are attracting considerable interests in human physiological activity monitoring and personal health management due to their capability for continuous,long-term,real time and comfortable monitoring both physiological and biochemical signals.Compared with traditional devices made of metal or semiconductor,various flexible sensors have excellent potential application in smart wearable devices due to their light weight and flexibility.As a flexible and porous material,conductive hydrogel has been used for sensing and energy storage.And in some cases,they can even be used for the collection and conversion of energies.Thus they have great advantages in the application of flexible wearable devices.This thesis mainly focuses on the preparation and electrical properties of graphene oxide-based hydrogels,especially on their self-power generation capability.The main research contents are as follows:（1）Polydopamine/graphene oxide（PDA/GO）composite hydrogel was prepared using water bath heating.The samples were characterized by X-ray diffraction（XRD）,Raman spectroscopy,scanning electron microscopy（SEM）,adhesion test,water content and swelling ratio test.The effects of graphene oxide content and reaction duration on the morphology,structure and properties of hydrogels were investigated.The self-power generation behavior of PDA/GO hydrogels under applied load was studied by an electrical test system.The results showed that when a certain pressure was applied to the hydrogel filled with Na Cl solution,the electrical current could be generated in the hydrogel,and the output current increased with the increase of applied pressure.The maximum output current can reach 1.5μA at 5 g.（2）In order to further improve the mechanical properties of graphene oxide-based hydrogels,sodium alginate/graphene oxide（SA/GO）hydrogels were prepared by solution mixing,in which the crosslink of sodium alginate with Ca²⁺took place and graphene oxide was used as a reinforcing filler and conductive filler.By adjusting the content ratio of sodium alginate to graphene oxide,the self-powered graphene oxide-based hydrogels with adjustable mechanical properties were prepared,and their structure and properties were studied.Under60%deformation,its compressive strength can reach 160 k Pa,and the swelling test shows that the swelling rate of hydrogel decreases with the increase of GO content,the maximum swelling rate is 700%,and the surface roughness of hydrogel increases with the increase of GO content.The self-power generation capability of the hydrogel was characterized by the electrical test system,and the effect of GO content on the self-power generation capability of the hydrogel was investigated.The results show that the high concentration of GO has an enhancement effect on the spontaneous electrical properties of the hydrogel.The SA/GO composite hydrogel exhibits a certain self-generating behavior when containing pure water and sodium chloride solution,and can produce higher power output when containing sodium chloride solution.Under the pressure of 40 g,the response of Na Cl solution to hydrogel current can be increased by 100%.（3）Polydopamine was further used to modify graphene oxide.The PDA-modified graphene oxide was cross-linked with sodium alginate and calcium chloride to prepare polydopamine/sodium alginate/graphene oxide/（PDA/SA/GO）hydrogel.The structure and self-powered behavior were studied.The results showed that PDA/SA/GO had higher conductivity and better self-power generation capability than SA/GO hydrogel,Its conductivity is twice that of SA/GO hydrogel,reaching 1.612 S/m.Under the load of 40 g,the current response of PDA/SA/GO hydrogel is 20%higher than that of SA/GO,reaching 0.06μA.The hydrogel has a wide bending sensing recognition range（0°-90°）and a more accurate load recognition range（0 g-40 g）.The sensing response can reach 28.7%and 10.6%,respectively.