Microscale shaping and rounding of ridge arrays and star pattern features on nickel mould via electrochemical polishing

High quality micro mould tools are critical for ensuring defect-free production of micro injection moulded products.The demoulding stage of the micro injection moulding can adversely affect the surface integrity due to friction,adhesion and thermal stresses between the metallic mould and polymeric replicated part.In the present work,we propose the use of precision electropolishing(EP)as a shaping and polishing process to control the draft angle and fillet radius of micro features in order to ease demoulding.Typical defects that occur in replicated polymer parts include cracks,burrs and distorted features.A nickel mould having multiple linear ridges and star shape patterns was designed for the present investigation to have characteristic dimensions ranging from 10μm to 150μm and with various aspect ratios to study the effect of electropolishing on modifying the shape of micro features and surface morphology.A transient 2D computational analysis has been conducted to anticipate the effect of shaping on the Ni mould after electrochemical polishing with non-uniform material removal rates,based on the distribution of current density.The experimental results indicate that after shaping using EP,the draft angle of star-patterns and linear patterns can be effectively increased by approximately 3.6°,while the fillet radius increases by up to 5.0μm.By controlling the electropolishing process,the surface roughness can be maintained under 50 nm.This work uses a green and environmental friendly nickel sulfamate electrolyte which can be effective for shaping of nickel micro features without causing any surface deposition.

In vitro antilithiatic activity of the hydro-alcoholic extract of Cinnamomum zeylanicum Blume bark on calcium oxalate crystallization

Objective: The study examines the effect of the hydro-alcoholic extract of Cinnamomum zeylanicum Blume bark on crystallization of calcium oxalate. Methods: The antilithiatic effect of various concentrations of the hydro-alcoholic extract of C. zeylanicum was investigated at various stages of stone formation, using Cystone as a stan da rd refere nee drug. The effect on calcium oxalate crystallization was evaluated by measuring the change in turbidity over time, during crystal nucleation, growth and aggregation, in the metastable solution of calcium chloride and sodium oxalate. The slope from the change in turbidity over time was measured using a spectrophotometer at 620 and 214 nm in respective tests. The inhibition rate was estimated by comparing turbidity in the presence and absence of extract. Crystals formed under experimental conditions were observed under a light microscope, and number and shape of the crystals were assessed in a randomly selected field. Phytochemical analysis and high-performance thin-layer chromatography of the extract was also carried out. Results: C. zeylanicum significantly reduced crystal nucleation at concentrations of 4, 8 and 10 mg/mL (P< 0.001). The inhibition percentage of crystal growth was between 28.30% and 92.46% in the presence of C. zeylanicum extract and from 20.76% to 64.15% with various concentrations of Cystone. The maximum inhibition of crystal growth was obtained from C. zeylanicum at 2 mg/mL (92.46%). Microscopic examination revealed a reduction in the number and size of crystals. In the aggregation assay, the inhibition percentage of C. zeylanicum was between 16.27% and 100%, while Cystone was from -214.68% to 100% at different concentrations. The highest (100%) inhibition of aggregation was found at 4 mg/mL of both the test and standard drugs. Conclusion: We found that C. zeylanicum hydro-alcoholic extract has notable inhibitory effects on various stages of crystallization, in terms of turbidity of solution, as well as the crystal size, number and morphology.