Study On The Preparation And Applications Of Surface Wrinkles Of Polymethyl Methacrylate

Surface wrinkling is a very common phenomenon in nature and human life.Surface wrinkling can be widely used in many fields such as the physical characterization of thin film materials,gratings and flexible electronic devices.If the morphology of surface wrinkles can be controlled by external stimuli,the changes in the wrinkles morphology can further affect the surface adhesion,wettability and optical properties of the material,and there will be greater application potential in the fields of optics,electronics,medicine,and smart sensing,so the construction of intelligent and dynamic micro-nano wrinkles patterns that can respond to external stimuli on the surface of the material is of great research value and significance.In this thesis,the surface wrinkles of the PMMA/PDMS film-substrate composite system that responds to the dual stimuli of temperature and ultraviolet light has been prepared.The effects of parameter adjustment during the preparation process on the wrinkle morphology,the response behavior and mechanism of the wrinkles to dual stimuli,and the application of wrinkles in optical and electrochemical sensors were studied.The specific research content is as follows:（1）A rigid film of PMMA is obtained by spin coating on a PDMS elastomer substrate to construct a film/substrate system,and then the surface of the PMMA/PDMS system is caused to get disordered labyrinth folds by means of heat induction.The wavelength and amplitude of the wrinkles can be precisely controlled by the three parameters of PMMA film thickness,PDMS main agent/curing agent ratio,and heating temperature.Under the stimulation of temperature and ultraviolet light,the wavelength of the wrinkles remains basically unchanged,the amplitude changes with the stimulation,and the change of wrinkle morphology under temperature stimulation is dynamically reversible.After 25 heating/cooling cycles,the amplitude and wavelength of wrinkles remain basically unchanged.The change of wrinkle morphology will affect its optical properties,and the wrinkled sample under temperature stimulation can complete the reversible cycle from fuzzy to transparent,thus realizing the application in smart windows.（2）Both PMMA and PDMS have a light transmittance of more than 90%,and the surface wrinkle structures has a refraction effect on light.Therefore,the dual stimulus response type PMMA/PDMS surface wrinkles are applied to the light diffuser.Plane geometric optics is used to analyze the light diffusion mechanism of the adjustable light diffuser based on the wrinkle structure.And the effects of wrinkle structures of different sizes,temperature and ultraviolet light stimulation on the regulation of light diffusion were explored by experiments.The area of the maximum aperture of the diffused spot obtained by samples of different sizes of folds ranges from 185.6 cm² to 537.4 cm².Under temperature stimulation,the area ratio of the diffused spot decreases from 38%at room temperature（25±2°C）to 1.7%after heating at 90°C for 10s.During the cooling process,the area ratio of the diffused spot increases from 1.7%after heating at 90°C for 10s increased to 34%after 180s of cooling.Under the stimulation of ultraviolet light,the area ratio of the diffused spot is reduced from 35%without light to 5%after 400s of ultraviolet light.（3）The wrinkle structure has a large specific surface area,and when applied to an electrochemical sensor,a larger electrochemically active area and more electrochemically active sites on the electrode surface can be obtained.An enzyme-free H₂O₂ electrochemical sensor was fabricated by integrating Ti/Cu/Ag thin film on the surface wrinkle structure of PMMA/PDMS.In a PBS solution with a H₂O₂concentration of 5 m M,the reduction peak current density of the wrinkled electrode is0.49 m A·cm^-2 higher than that of a flat electrode without wrinkle structure.The sensitivity of the enzyme-free H₂O₂ electrochemical sensor based on the wrinkle electrode is 0.2026 m A·m M^-1·cm^-2,the detection limit is 0.2299 m M/L（the signal-to-noise ratio is 3:1）,the linearity is 0.9997,and the response time is within 4s.