The contact angles of distilled water and methanol solution on the wings of butterflies were determined by a visual contact angle measuring system. The scale structures of the wings were observed using scanning electr...The contact angles of distilled water and methanol solution on the wings of butterflies were determined by a visual contact angle measuring system. The scale structures of the wings were observed using scanning electron microscopy, The influence of the scale micro- and ultra-structure on the wettability was investigated. Results show that the contact angle of distilled water on the wing surfaces varies from 134.0° to 159.2°. High hydrophobicity is found in six species with contact angles greater than 150°. The wing surfaces of some species are not only hydrophobic but also resist the wetting by methanol solution with 55% concentration. Only two species in Parnassius can not resist the wetting because the micro-structure （spindle-like shape） and ultra-structure （pinnule-like shape） of the wing scales are remarkably different from that of other species. The concentration of methanol solution for the occurrence of spreading/wetting on the wing surfaces of different species varies from 70% to 95%. After wetting by methanol solution for 10 min, the distilled water contact angle on the wing surface increases by 0.8°-2.1°, showing the promotion of capacity against wetting by distilled water.展开更多
The effects of impacting particles from a jet of liquid on the removal of a surface material(on the impacted workpiece)were investigated.Experimental observations show that the cross section of the material removed ch...The effects of impacting particles from a jet of liquid on the removal of a surface material(on the impacted workpiece)were investigated.Experimental observations show that the cross section of the material removed changed fromʹWʹ‐shaped toʹUʹ‐shaped as the size of abrasive particles was increased.Comparisons between removed material profiles and particle collision distributions indicate that the particle-surface collisions are the main reason for the material removal.The deduced number of atoms removed by a single collision implies that a transition occurs in the removal mode.For nanoscale particles,the polished surface is likely to be removed in an atom‐by‐atom manner,possibly due to the chemisorption of the impacting particles on the impacted surface.Contrarily,for the case of microscale particles,bulk material removal produced by particle bombardment is more likely to occur.The present mechanism of material removal for particle-surface collisions is further corroborated experimentally.展开更多
文摘The contact angles of distilled water and methanol solution on the wings of butterflies were determined by a visual contact angle measuring system. The scale structures of the wings were observed using scanning electron microscopy, The influence of the scale micro- and ultra-structure on the wettability was investigated. Results show that the contact angle of distilled water on the wing surfaces varies from 134.0° to 159.2°. High hydrophobicity is found in six species with contact angles greater than 150°. The wing surfaces of some species are not only hydrophobic but also resist the wetting by methanol solution with 55% concentration. Only two species in Parnassius can not resist the wetting because the micro-structure （spindle-like shape） and ultra-structure （pinnule-like shape） of the wing scales are remarkably different from that of other species. The concentration of methanol solution for the occurrence of spreading/wetting on the wing surfaces of different species varies from 70% to 95%. After wetting by methanol solution for 10 min, the distilled water contact angle on the wing surface increases by 0.8°-2.1°, showing the promotion of capacity against wetting by distilled water.
基金The work is financially supported by the National Natural Science Foundation of China(Nos.51575054 and 51527901)the Fundamental Research Funds for the Central Universities(No.YX2013‐02).
文摘The effects of impacting particles from a jet of liquid on the removal of a surface material(on the impacted workpiece)were investigated.Experimental observations show that the cross section of the material removed changed fromʹWʹ‐shaped toʹUʹ‐shaped as the size of abrasive particles was increased.Comparisons between removed material profiles and particle collision distributions indicate that the particle-surface collisions are the main reason for the material removal.The deduced number of atoms removed by a single collision implies that a transition occurs in the removal mode.For nanoscale particles,the polished surface is likely to be removed in an atom‐by‐atom manner,possibly due to the chemisorption of the impacting particles on the impacted surface.Contrarily,for the case of microscale particles,bulk material removal produced by particle bombardment is more likely to occur.The present mechanism of material removal for particle-surface collisions is further corroborated experimentally.
