Design Of Automatic Release System With Ultra-low Speed And High Stability For PDMS Grating-like Wrinkled Template

Grating is an important optical component,which has been widely used in spectral analysis,photoelectric sensing,image recognition and other fields.Meanwhile,due to the periodicity of grating structure,it can also be used as a template to assist the preparation of nanoparticles chain array system.So how to prepare high quality grating structure is the key to improve the performance of related devices.Although the structure of grating is controlled by physical etching method(such as electron beam exposure and ion beam etching),the cost is high and processing time is long.In recent years,the grating-like structures prepared by plasma treatment of flexible substrate have attracted much attention.Among them,flexible substrate under tensile state(such as polydimethylsiloxane,PDMS)treated by plasma,a layer of glass-like film would be formed on surface.Then in the process of releasing substrate,because the difference of stress between the film and material,can form a grating-like wrinkled structure.This method does not need complex micro-nano processing technology,easy to operate,and the structural parameters of grating-like wrinkles can be effectively adjusted by changing the parameters such as tensile ratio and plasma processing time,so it is a good method to prepare grating structures at low cost.However,the problems of defects,cracks and low linearity may occur when the grating is prepared by plasma treatment of flexible substrate,which is not conducive to the requirements of related applications.From the formation mechanism of the grating structure,it can be seen that the parameters such as the velocity and stability of flexible substrate in the process of stretching and releasing are important factors causing the above imperfections.Based on this,standing on the study of how to improve the stability of substrate in the process of stretching and releasing,and how to control its speed effectively,a set of ultra-low speed stable automatic release system is designed to combine with the mechanical stretching device designed by us,a high quality grating-like wrinkled structure is prepared by using plasma treatment of flexible substrate.The main work of the dissertation includes:1.Design an automatic release system of ultra-low speed and high stability,which adopts the closed-loop drive control mode with the three-phase hybridstepping motor with built-in encoder as the core,which can realize the uniform and stable release as low as 20μm/min,and effectively improve the uniformity and stability of the substrate release process.On the basis of this system,a new mechanical compressing and stretching device is designed,which is mainly used to improve the module of compressing PDMS,furthermore greatly improve the linearity of wrinkles.2.The effect of substrate release rate on the defects of wrinkles were studied by using the automatic release system of ultra-low speed and high stability.Experimental results indicates: the smaller the release rate,the less the defects of the wrinkles are.Among them,the defects of the wrinkles with a period of 1～2μm are 21.7% less than that with a period of 50μm /min,and the wrinkles with a period of 2～3μm/min are 43.1% less than that with a period of1000μm/min.3.On the premise of stable release of the control system,starting from the "substrate-film" double-layer system formed by plasma treatment of PDMS,the modulus gradient of the double-layer system was changed by adjusting the process parameters generated by the plasma,so as to improve the cracks of wrinkles.The experimental results show that the automatic release system can stabilize the production wavelength of a certain wrinkles,gas pressure and power are the main factors affecting the cracks of wrinkles,and the reduction of gas pressure and power can reduce the cracks of wrinkles of the same wavelength by 46.6% and 26.6% respectively.Finally combining disks’ 1-dimensional grating structure and mechanical stretching-releasing process of forming wrinkles,the preparation of2-dimensional high quality grating-like template is realized,further enrich the application of PDMS wrinkles in grating field.