| Micro structure array is widely used in the field of material surface modification,such as medical treatment,MEMS,optics,architecture,transportation and so on.The traditional micro structure array processing method has the defects of expensive equipment,low production efficiency and poor product replication,which has certain limitations.With the advantages of simple forming equipment,high forming efficiency,simple process conditions and friendly environment,UV curable imprinting has been widely used in the field of micro nano manufacturing.Due to the nature of the crosslinking polymerization of macromolecules in the process of UV curing,the shrinkage of the UW curing material is larger than that of the traditional thermoplastic material,which greatly affects the replication accuracy of the micro structure array.In this paper,aiming at the problem of low precision in the preparation of micro structure array by UV curable imprinting,the shrinkage test of different components of UV curable materials was carried out,the low shrinkage UV curable formula was formulated,and the process optimization was carried out,and the high precision micro structure array was successfully prepared.The main research contents are as follows:1.Based on the UV Curing injection molding equipment designed and manufactured in the early stage of the laboratory,a set of UV curing process shrinkage testing device is designed and manufactured,mainly including mold module,injection module,irradiation module and control module.The device calculates the molding shrinkage of UV curing material system by measuring the size of the shrinkage,which has the advantages of simple operation and convenient testing.Through the combination of electric and pneumatic control equipment injection curing test demoulding,the semi-automatic measurement is realized.2.The effect of different process conditions and components(oligomer and active diluent)of UV curing materials on the mechanical properties and shrinkage of products was studied by using the self-developed UV curing shrinkage testing device,and the formula of low shrinkage materials suitable for UV curing imprinting was developed.3.The master plate of the micro structure array was prepared by photolithography,and then the PDMS transparent die for stamping was prepared.The influence of pressure maintaining,irradiation time and irradiation intensity on the precision of the micro structure array products was investigated by using the self-made photocuring press in the laboratory.The results show that the surface of the micro structure array cells prepared under the best technological conditions still has the phenomenon of surface depression.Combined with the mechanism of UV curing reaction,the embossing process was improved.Firstly,the short wavelength UV light was used to irradiate the UV curing material,and then the medium band UV light was used to cure the material.The cylindrical micro structure array with high replication degree of 98.13%and cylinder diameter replication degree of 97.89%was successfully prepared,which solved the problem of surface depression of micro structure unit.4.Aiming at the defects of the micro structure array products after the embossing experiment,the process of the separation of the micro structure array products from the PDMS mold was simulated and analyzed,and the causes of the defects of the micro structure array were revealed.According to the simulation model,the effects of the demoulding time,the friction coefficient and the modulus of elasticity of the mold on the stress of the micro structure unit were studied.The results showed that the demoulding time was properly extended and the friction coefficient was reduced,By improving the modulus of elasticity of the die,the defects of the surface missing and crystal breaking of the microstructure can be effectively solved,and the fabrication accuracy of the microstructure array can be improved. |
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