| In the past two decades,nanowire synthesis technology has been quite mature,with the rapid development of nanotechnology.It's convenient to achieve mass-production and low-cost production of various nanowires.Because the diameter of the nanowire is at the nanometer scale,the quantum effect becomes more obvious,resulting in that nanowires have unique optical properties,mechanical characteristics,and thermal and electrical transmission features,etc.,which have many important applications in the field of science and technology.Controllable manipulation and functional assembly of one-dimensional nanomaterials can improve the overall functional characteristics and realize the manufacture of nano-functional devices.The controllable manipulation and assembly technology of nanowires is one of the key scientific issues in the future application research and development of one-dimensional nanomaterials.The research and development of large-scale manipulation and assembly technology of nanowires,to meet the assembly requirements of nanometer functional devices,has important theoretical and practical significance.This article reviewed the nanowire manipulation and assembly technique and dielectrophoresis technology.On the basis of traditional dielectrophoretic manipulation techniques,this paper proposed the isolated dielectrophoretic assembly of nanowires,which will realize the large-scale,batch and repeatable assembly for nanowires,and researched the application of assembled silver nanowire structures.The specific research results are summarized as follows:(1)Theoretical analysis of isolated dielectrophoretic manipulation of nanowires and simulation of the percolation process of silver nanowire electrode network were carried out.With the application of the dielectrophoresis theory and ac electrokinetic theory,the paper analyzed the axial and radial force and steering torque of nanowires during dielectrophoretic manipulation,and theoretically studied the effect of length to diameter ratio,electrical characteristics,solution conductivity and signal frequency on dielectrophoretic force applied on nanowires;the influence of the electric field distribution above the assembly substrate and the thickness of the assembly substrate on the assembly of nanowires in the isolated dielectrophoresis chip was researched to optimize the parameters of the assembly substrate.At the same time,the influence of voltage and frequency of applied electrical signal on the assembly of nanowires in the isolated dielectrophoresis was explored to choose the proper electrical signal and provided the theoretical basis for chip design and system integration.In addition,through percolation theory,the article simulated and compared the conductivity and transparency of the random and aligned nanowires,demonstrating the superiority of aligned silver nanowires in optoelectric devices,which provides the theoretical support for aligned silver nanowires as the flexible transparent conductor.(2)Aligned assembly of nanowire arrays and multiple-step assembly by isolated dielectrophoresis were demonstrated.This paper developed the isolated dielectrophoresis chip and the corresponding experimental platform to realize the precise manipulation and assembly of nanowires on the assembly substrate.The principle and process of isolated dielectrophoresis chip were studied.The preparation of dielectrophoresis chip involved material selection of electrode substrate,electrode structure design and manufacture,and the selection of assembly film material and thickness,etc.With isolated dielectrophoresis chip and experimental platform,the nanowire arrays and networks on flexible transparent films were assembled using the interdigitated electrode and finger tip electrode as the electrode base.In this paper,a model for quantitative evaluation of nanowire alignment was proposed to research the effect of electrical signal amplitude,frequency and film thickness on the nanowire assembly.At the same time,multi-step assembly and batch assembly of nanowires can be realized by rotating or replacing the assembly substrate.The photoelectric performance of the assembled nanowire film was tested to compare randomly distributed nanowire film and aligned nanowires.(3)Biosensors for detection of circulating tumor cells were prepared by assembling nanowires through isolated dielectrophoresis technology,and low concentration of MCF-7 cell samples were tested.Firstly,isolated dielectrophoresis technique was employed to assemble nanowire array structure on the thin film substrate,then a layer of graphene oxide was laid on the nanowire structure,and the nanowires/GO substrate modified with antibody Ep-CAM was used to form the detection substrate.The microchannel chip with herringbone structure on the upper layer of the flow channel was processed by laser processing,and the microchannel chip was bonded with the detection substrate to prepare a biological detection chip for detecting circulating tumor cells.The sorting chip was integrated in front of the capture chip,and the sample solution was pretreated with circulating tumor cell sorting,and then the circulating tumor cells were captured by the detection chip and counted with the fluorescent microscope.The research explored the influence of herringbone groove structure,base structure,antibody and sample liquid velocity on cell capture efficiency,and found that wide groove pitch herringbone structure and low velocity would further improve the efficiency of cell capture,and the Ep-CAM modified nanowires/graphene oxide base could get the capture efficiency of about 86% and be used for detection of circulating tumor cells in the low concentration even to100 cells/m L.(4)A flexible transparent heater was prepared by assembling silver nanowires using the isolated dielectrophoretic assembly,to explore the application of the assembled nanostructure in the new generation of flexible transparent heaters.Based on the isolated dielectrophoresis,silver nanowire networks were assembled on the PET film,and then a layer of graphene was covered on the nanowire structure as a protective layer.At last,the assembled silver nanowires and graphene structure was annealed to reduce the contact resistance between silver nanowires and make nanowire structure and graphene combine tightly.Then the paper researched the heating properties,oxidation resistance,flexibility and stability of the flexible transparent heater,and the experimental results showed that Ag NWs/Graphene hybrid film had good oxidation resistance and mechanical flexibility,fast response and heating uniformity,high reliability,with the great potential for fabricating a new generation of flexible transparent heaters.Finally,the reaseach carried out an experimental study on the defogging function of the flexible heater,and the results showed that the Ag NWs/Graphene defogging devices had good defogging effect and fast response,which would broaden the application range of assembled nanowire structures by the isolated dielectrophoresis technology and lay a foundation for further application in the future. |
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