Microinjection Compression Molding And Light Trapping Properties Of Micro-/nanostructured Surfaces

Products with optical microstructures on their surfaces are becoming more and more widely used.Transparent products with light trapping surface can reduce the surface reflectance and enhance the light transmittance.Opaque products with light trapping surface can increase the color saturation of the colored product.Additional property such as self-cleaning further broadens the application of light trapping surfaces.In this dissertation,mold inserts with microstructures were fabricated.Microinjection compression molding was used to mold the samples with light trapping effect.The formation mechanism of the micro-/nano-structures and the optical properties,wetting state and adhesion properties were analyzed.Nickel templates with micro-/nanostructures on their surfaces were prepared.The etched silicon wafer and the red rose petal were used as prototypes.By combining electroless plating and electroplating,the micro-pyramidal structure and the hierarchically micro-/nanostructured micro-papillae on surfaces of prototypes were accurately replicated to the surfaces of nickel templates.Nickel templates with negative micro-/nanostructures were obtained.The influence of mold temperature,melt temperature,and mold compression force on the replication fidelity of micro-pyramidal structure on the polystyrene(PS)replica surface was investigated by response surface experiment.The results showed that the mold temperature had the most significant impact on the replication fidelity of micro-pyramidal structure,and the melt temperature had a greater impact than that of mold compression force.Increasing the mold temperature,melt temperature,and mold compressive force within a certain range could improve the replication fidelity of micro-pyramidal structure.With a nickel template with negative micro-pyramidal structure as mold insert,micropyramidal structured PS replicas with good light trapping effect were prepared by microinjection compression molding.Compared to its PS counterpart,the PS replica had a much lower reflectance and enhanced light transmittance.The results of the simulation showed that the light transmittance of PS replica at different angles of incidence was significantly higher than that of its PS counterpart.When the PS replica was used as a protective layer of the thin film solar cell,the photoelectric conversion efficiency of the solar cell under vertical and oblique light incident were increased.With a nickel template with negative hierarchically micro-/nano-structured micro-papillae as mold insert,polypropylene(PP)and PS replicas with hierarchical micro-/nano-structure consisting of micro-papillae and nanofolding were prepared by microinjection compression molding.Both replicas have lower reflectance and the PS replica had an enhanced transmittance.Changing the mold temperature could gradually tune the water droplet adhesion on superhydrophobic surfaces of PP replica over a wide-range.Hence,superhydrophobic PP surfaces exhibiting low,medium,high and extremely high adhesion can be prepared.