The Assembly,Modification and Applications of Graphene-based Materials Based on Microfluidic

Author:Dong Yue

Supervisor:liu bi feng


Degree Year:2019





Graphene-based materials as star materials have attracted more and more attention,which own excellent mechanical,optical,electrical,thermal properties,large specific surface area and outstanding biocompatibility,and has been used in biomedicine,energy storage,sensing,environmental remediation,flexible display and other fields.However,owing to the immaturity of the preparation process for graphene-based materials,their sheet size are different,which make their performance extremely unstable and cannot be applied practically.In order to solve the problem,scientists have tried to assemble the sheets of graphene-based materials into stable graphene-based assemblies to broaden their application fields by making use of the average effect and synergistic effect between them.A variety of assembly methods have been reported to enable zero-,one-,two-,and three-dimensional assembly of graphene-based materials,which are expected to be applied to real life,for example,zero-dimensional graphene-based microspheres for environmental remediation,one-dimensional fibrous graphene electrodes for painless minimally invasive medical testing,and two-dimensional graphene-based films for wearable electronic devices.However,there are many disadvantages for existing methods such as high cost and energy consumption,difficulty in mass production,and poor reproducibility of preparation,and it has not been found that the assemblies can be easily prepared by an assembly method to meet the diverse requirement for different applications.In this work,we adopt microfluidic technology to assemble the graphene-based materials,making full use of the unique advantages of microfluidic technology in material assembly and precise modification,such as precise fluid control,Low energy consumption,high-volume parallel preparation,etc.Finally,five graphene-based material assemblies with different structural forms are easily prepared by microfluidic technology,including zero-dimensional spherical GO-based janus micro-motor,one-dimensional graphene fiber with special structure and property,two-dimensional graphene hydrogel-based planar interdigital microsupercapacator,two-dimensional GO/PPy film-based double-layer actuator and the three-dimensional helical graphene-based micromotor,and explored their applications in biochemical pollution repair,cancer detection,energy storage and biomimetic actuator.Nowadays,there are few reports about the assembly of graphene-based materials by microfluidic technology.The main results of this paper are as follows:(1)Zero-dimensional sphere-like graphene oxide(GO)-based janus micromotors were fabricated with high uniformity and output based on the coaxial glass capillary microfluidic.Different shapes of micromotors were prepared by adjusting the concentration of GO-based materials,and spherical micromotors with different sizes were prepared by adjusting the flow rates of the oil phase and the GO-based materials.The movement trajectories and speed of the micromotors driven by H2O2 fuel are related to the H2O2 concentrations,and their direction of movement can be controlled by a magnetic field.The micromotors can remove the tetracycline from wastewater quickly,and the removal efficiency is related to the number of micromotors,time of propulsion and pH of solution.The adsorption isotherm model and adsorption kinetics are in accordance with the Freundlich model and quasi-secondary kinetics,respectively.(2)A variety of glassy capillary microfluidic devices for fiber spinning were assembled based on glass capillary tube and SU-8 molds.By adjusting the fluid types in different capillaries,shaped,multi-hollow,multi-hetero,heterogeneous hollow graphene-based fiber was successfully prepared.The proportion of the hollow and heterogeneous portions in the graphene-based fiber can be regulated by adjusting the flow rate.Considering the large specific surface area of the hollow graphene fiber,Pt nanoparticles were successfully modified on the inner and outer surfaces of the fiber.The modified fiber can detect H2O2 released from cancer cells with high sensitivity,and exhibit different sensitivity for different types of cancer cell.(3)Three-dimensional helical graphene-based micromotors were successfully prepared by introducing oil phase,a mixed solution of GO and Fe3O4(GOF)and sodium alginate into the double coaxial glass capillary microfluidic device.The shape,pitch,length and wire diameter of the micromotors are related to the flow rates of the three fluids and the concentration of GOF and sodium alginate.Upon reduction and natural drying,smaller graphene-based helical micromotors were obtained,which can be driven quickly under a rotating magnetic field and can purify dye wastewater quickly.The graphene-based spiral micromotor modified by Ag nanoparticles can remove pathogen in water quickly.(4)Based on paper chip and vacuum filtration technology,Ag nanoparticles and graphene gel(GH)were successfully deposited into the channels of paper chip with high precision,and further assembled to obtain two-dimensional GH-based planar interdigital microsupercapacitor(GH-mSC).The GH-mSC has high rate performance,high specific capacitance,excellent cycle stability,good flexibility,high energy density and power density.Multiple GH-mSCs are connected in series and parallel,and the output voltage and specific capacitance of the mSC can be effectively improved.For example,four GH-mSCs connected in series can illuminate the LED light.Through our proposed method,GH-mSC can be prepared on both sides of the paper chip,so that the volume of the energy storage device can be further reduced.(5)Based on the agarose chip stamp,polypyrrole(PPy)was precisely modified on the surface of GO film to obtain a two-dimensional GO/PPy film-based actuator.The actuator has excellent actuating performance under the stimulation of RH,IR light and temperature,and has different deformation under stimulation for the GO/PPy actuators with different PPy pattern.Inspired by the claw of hawk and climbing plants,we have obtained the cross-shaped and spiral-shaped smart grippers by modifying cross-shaped and diagonal stripe array of PPy on GO film,which can be used to grab weights that are dozens of times heavier than their own weight.In addition,inspired by the inchworm,we designed a soft robot that can move forward under humidity stimulation.In summary,this paper realizes zero-,one-,two-,three-dimensional assembly and precise modification of graphene-based materials by microfluidic technology,and these assemblies have shown excellent performance in biochemical pollution repair,cancer detection,energy storage,biomimetic actuator and other aspects.These research work in this paper combine microfluidic chip technology with the preparation of graphene-based material assemblies,which further enhance the possibility of industrial production and practical application of graphene-based material assemblies.