Research On The Machining Technology Of Microstructures On SERS Substrates Tip-based On The Arrayed Indentation Method

With the rapid development of micro/nanotechnology,micro/nanostructures are increasingly employed in the fields of nanophotonics,microfluidics and microelectronics.Micro/nanostrucures can be used as Surface-Enhanced Raman Scattering(SERS)substrate in the detections of biomolecule,flammable substances,and toxic pesticide residues.Therefore,how to fabricate surface-enhanced Raman substrates with high quality,sensitivity,efficiency and enhancement factor,are significant for researchers all over the world.It is worth noting that the method of tip-based mechanical machining can be used to fabricate complex three-dimensional micro/nano structures with high efficiency in a wide processing range.However,the present studies about fabrication of SERS substrate are still in the initial stage of verfication and lack in-depth theoretical research and process optimaization with the method of tip-based mechanical machining.Therefore,according to the issues mentioned above on the fabrication of SERS substrates,the mehod of force control mechanical machining is studied in the aspects of machining mechanism,machining technology and application,in order to realize the technical foundation of the precise SERS substrates.The detailed contents of this thesis contain:The machining system based on force control is established and analysed.Firstly,the micro/nano machining device based on force control is established.A UMAC controller,a piezoelectric displacement,a force sensor and a pyramidal diamond tip are chosen as core components and the closed-loop force control system is realized during machining.Secondly,the system based on the force control is established to study the stability of system.The stability of the force control system and the force influenced by the parameters of control system are analysed during machining in detail.The processing principle and experimental research of micro-groove under the condition of force open-loop and closed-loop are compared.In addition,the maximum machining speed of the device is investigated to improve the efficiency of the machining system.Finally,when the force control is constant during machining,the large-scale three-dimensional structure are achieved with the contorlled dimensions that the length vary from a few microns to several hundred microns and the depth varies in a few microns on the aluminum(2A12)and single crystal copper surface.The mechanism of cavities based on arrayed indentation method has been studied with the method of experiment and finite element simulation.Fisrtly,the cube corner tip is used as a tool to fabricate the sample using the force system.The complex arrayed indentation cavities are fabricated by trajectory program of the movement stage.A method of arrayed cavities is proposed to improve the processing efficiency,which demonstrates that tip-based indentation method has an ability to machine more complex structures.Finally,a three-dimensional finite element simulation models of the plastic deformation of single crystal copper(110)based on triangular pyramid tip have been established by the Abaqus software.The height of pile-up,the depth and the stress distribution of single and multi-point cavities were studied,respectively.The height of pile-up,variation of the depth and stress distribution of cavities are revealed by extrusion deformation of material,providing a reference as the Surface-Enhanced Raman Scattering substrate subsequently.A new method of the combination of tip-based arrayed indetation and soft imprinting technology is proposed to fabricate SERS substrates.The Raman enhancement of the probe molecule is influenced by the size of different arrayed pyramid structures after transferring.The Raman enhancement of the probe molecule is studied to obtain the optimal thickness of gold film on the arrayed micro/nano structures.Finally,the Raman intensity of coated gold arrayed micro/nano structures are analyzed with the same detected condition on the PDMS surface and commercial Q-SERS,respectively.The method of the fabrication of coated gold arrayed micro/nano structures is proved by detecting the Raman intensity of the probe molecule with a high resolution.A new method that combines tip-based arrayed indentation technology with chemical redox reaction is proposed to fabricate hybrid SRES substrates.Firstly,The effects of the morphology of the micro/nano cavities and the Raman intensity of the probe molecule are studied by the time of corrosion in Ag NO3 solution.Secondly,the Raman signal intensity of the different numbers and size of nanoparticles is studied by the optical module of comsol software.Studies show that the diameter of the nanoparticle is 200 nm,the Raman intensity of the probe molecule is the highest.The effect of the Raman intensity is studied to combine different particle structures with cavities.The optimal machining structure is achieved by comparing the simulation results with experimental results.Finally,one or two the arrayed structures chosen with better SERS enhancement can be used to dectect malachite molecules which is a carcinogens commonly used in aquatic products.The detection of malachite green molecules using the microstructures fabricated by this method can reach the national standard.