Study On Curved Surface Microstructures Forming Based On Temperature Controlled Capillary Effect Of PDMS–SU-8 Interface

With the development of micro-optics and microfluidic,micro-devices with curved surface microstructures have been applied more and more widely.In order to meet the functional requirements and apply to the corresponding scenes,the methods of mass manufacturing curved surface microstructures arrays on various materials with specific technologies have been proposed.The curved surface microstructures machining technologies with the characteristics of simple,stability,precision and economy are of great value to the production and application of corresponding products.Compared with other methods,using capillary effect to fabricate surface microstructures has many advantages.For example,no expensive equipment is needed,the surface quality is very high,the production cycle is short,and the capillary effect can be adjusted in many ways to realize flexible fabrication.This thesis focuses on the capillary effect molding technology and mainly does the following work:Firstly,SU-8 photoresist microsphere crown arrays with various heights and depths from convex to concave were fabricated by adjusting the molding temperature in the laboratory.Then soft lithography was used to fabricate PDMS microsphere crown arrays.Through optical characterization and imaging experiments,it was proved that these two kinds of microsphere crown arrays have the function of microlens arrays.In order to study the relationship between the crown heights of SU-8 photoresist microsphere crown arrays and the forming temperatures,the crown heights data of SU-8 photoresist microsphere crown arrays were measured at different forming temperatures,and the conclusion was drawn that the crown heights changed from large to small and from positive to negative as the temperature increased at 10-110℃.Secondly,the influence of temperature on the shape of the microsphere was explored.It was explained that the formation of curved liquid surface is affected by surface tension,liquid-solid contact angle and pressure on both sides of the liquid surface.Then,the surface tension of SU-8 2015 photoresist at different temperatures and the contact angle of liquid SU-8 2015 photoresist on PDMS surface at different temperatures were measured through experiments,which provided data for the subsequent simulation.Taking curved liquid surface and part of liquid column as the research object,the mechanical balance between convex liquid surface and concave liquid surface was analyzed,and the basis of its stable existence was determined.In order to further study the forming process of curved liquid surface,a simulation model was established using COMSOL Multiphysics simulation software,and the influences of surface tension,contact angle and pressure difference on the shape of liquid surface were analyzed in detail.After the experimental results were simulated and the forming mechanism was verified,the simulation software was used to simulate the models with other scales and shapes,and the influences of circular holes with different scales,strip array,concentric ring,oval,regular polygon and other shapes on the capillary effect were studied.Through the simulation results,it can be predicted that this molding technology can be used to process a variety of microstructures,which provides a new idea for the fabrication of microstructures.