In this study,a theoretical model was established for predicting the equilibrium shape of the droplet on flat and spherical surfaces.The theoretical equilibrium shape of heavy droplets could be obtained once contact a...In this study,a theoretical model was established for predicting the equilibrium shape of the droplet on flat and spherical surfaces.The theoretical equilibrium shape of heavy droplets could be obtained once contact angle and volume of droplets were given.It showed that the predictions of the theoretical flat model were in good agreement with the shape obtained by Surface Evolver when the contact angle is below 120 and the droplet size is on the order of capillary length.This available range will decrease and increase when the heavy droplet is on convex and concave spherical surface,respectively,in contrast to that on flat surface.The available range will decrease more for higher curvature of convex spherical surfaces.展开更多
Three-dimensional(3D)printed re-entrant micropillars have demonstrated high static contact angles for an unprecedented variety of liquids,but have yet to achieve this with low contact angle hysteresis and excellent ab...Three-dimensional(3D)printed re-entrant micropillars have demonstrated high static contact angles for an unprecedented variety of liquids,but have yet to achieve this with low contact angle hysteresis and excellent abrasion resistance.We report on the demonstration of 3D printed microcell/nanoparticle structures that exhibit high static contact angle,low contact angle hysteresis,and high mechanical durability.Micropillars and microcells both exhibit high static contact angles with water and ethylene glycol(EG),but suffer from high contact angle hysteresis,indicative of rose petal wetting.Our modeling results indicate that micropillars are able to achieve higher static contact angle and breakthrough pressure simultaneously compared with microcells.However,simulations also indicate that micropillars have higher maximum equivalent stress at their bases,so that they are more prone to mechanical failure.We address contact angle hysteresis and mechanical durability issues by the creation of 3D printed microcell/nanoparticle arrays that demonstrate super-repellency and retain their super-repellency after 100 cycles of mechanical abrasion with a Scotch-Brite abrasive pad under a pressure of 1.2 kPa.The use of interconnected microcell structures as opposed to micropillars addresses mechanical durability issues.Low contact angle hysteresis is realized by coating 3D printed structures with low surface energy nanoparticles,which lowers the solid–liquid contact area fraction.Our results demonstrate new 3D printed structures with mechanical durability and super-repellency through the use of microcell structures integrated with fluorinated nanoparticles.展开更多
Electrochromic transition metal oxides(ETMOs)are useful in energy saving devices and smart indicators.Among these ETMO candidates,titanium dioxide(TiO_(2))is intriguing for its abundance and environmental safety,but t...Electrochromic transition metal oxides(ETMOs)are useful in energy saving devices and smart indicators.Among these ETMO candidates,titanium dioxide(TiO_(2))is intriguing for its abundance and environmental safety,but the low color efficiency and slow coloring rate are still barricades to promote its electrochromic application.Herein,we demonstrate an amorphization strategy to comprehensively enhance the performance of TiO_(2) nanowire film(TNF)via atomic layer deposition(ALD)of an additional TiO_(2) conformal layer onto TNF surface,of which the layer structure evolves successively from ordered to disordered,achieving tunable electrochromism by controlling ALD cycles.Besides the remarkable increment of charging efficiency by~35% and color efficiency by~40%,bleached transmittance rectified optical density(BTR density)and ion diffusion coefficient are boosted by~90% and over 15 times,respectively for TNF deposited with 150 cycles.A large number of self-doped Ti^(3+) defects and hydroxyl units together with order-disorder interconnections in the ALD TiO_(2) layer are responsible for the performance enhancement.The concept for successively evolving surface structure shares the feasibility of upgrading conventional ETMOs as well as designing new electrochromic materials.展开更多
This article concerns the construction of high-order energy-decaying numerical methods for gradient flows of evolving surfaces with curvature-dependent energy functionals.The semidiscrete evolving surface finite eleme...This article concerns the construction of high-order energy-decaying numerical methods for gradient flows of evolving surfaces with curvature-dependent energy functionals.The semidiscrete evolving surface finite element method is derived based on the calculus of variation of the semidiscrete surface energy functional.This makes the semidiscrete problem naturally inherit the energy decay structure.With this property,the semidiscrete problem is furthermore formulated as a gradient flow system of ODEs.The averaged vector-field collocation method is used for time discretization of the ODEs to preserve energy decay at the fully discrete level while achieving high-order accuracy in time.Extensive numerical examples are provided to illustrate the accuracy and energy diminishing property of the proposed method,as well as the effectiveness of the method in capturing singularities in the evolution of closed surfaces.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 10902015)the Research Funds for the Doctoral Program of Higher Education of China (Grant No. 20091101120001)
文摘In this study,a theoretical model was established for predicting the equilibrium shape of the droplet on flat and spherical surfaces.The theoretical equilibrium shape of heavy droplets could be obtained once contact angle and volume of droplets were given.It showed that the predictions of the theoretical flat model were in good agreement with the shape obtained by Surface Evolver when the contact angle is below 120 and the droplet size is on the order of capillary length.This available range will decrease and increase when the heavy droplet is on convex and concave spherical surface,respectively,in contrast to that on flat surface.The available range will decrease more for higher curvature of convex spherical surfaces.
基金supported in part by the National Science Foundation(No.ECCS 1552712).
文摘Three-dimensional(3D)printed re-entrant micropillars have demonstrated high static contact angles for an unprecedented variety of liquids,but have yet to achieve this with low contact angle hysteresis and excellent abrasion resistance.We report on the demonstration of 3D printed microcell/nanoparticle structures that exhibit high static contact angle,low contact angle hysteresis,and high mechanical durability.Micropillars and microcells both exhibit high static contact angles with water and ethylene glycol(EG),but suffer from high contact angle hysteresis,indicative of rose petal wetting.Our modeling results indicate that micropillars are able to achieve higher static contact angle and breakthrough pressure simultaneously compared with microcells.However,simulations also indicate that micropillars have higher maximum equivalent stress at their bases,so that they are more prone to mechanical failure.We address contact angle hysteresis and mechanical durability issues by the creation of 3D printed microcell/nanoparticle arrays that demonstrate super-repellency and retain their super-repellency after 100 cycles of mechanical abrasion with a Scotch-Brite abrasive pad under a pressure of 1.2 kPa.The use of interconnected microcell structures as opposed to micropillars addresses mechanical durability issues.Low contact angle hysteresis is realized by coating 3D printed structures with low surface energy nanoparticles,which lowers the solid–liquid contact area fraction.Our results demonstrate new 3D printed structures with mechanical durability and super-repellency through the use of microcell structures integrated with fluorinated nanoparticles.
基金This work was supported by the National Natural Science Foundation of China(21805265)Fundamental Research Funds for the Central Universities(WK2060190094,WK2480000005)the National Synchrotron Radiation Laboratory Joint Fund Project(KY2060000109).
文摘Electrochromic transition metal oxides(ETMOs)are useful in energy saving devices and smart indicators.Among these ETMO candidates,titanium dioxide(TiO_(2))is intriguing for its abundance and environmental safety,but the low color efficiency and slow coloring rate are still barricades to promote its electrochromic application.Herein,we demonstrate an amorphization strategy to comprehensively enhance the performance of TiO_(2) nanowire film(TNF)via atomic layer deposition(ALD)of an additional TiO_(2) conformal layer onto TNF surface,of which the layer structure evolves successively from ordered to disordered,achieving tunable electrochromism by controlling ALD cycles.Besides the remarkable increment of charging efficiency by~35% and color efficiency by~40%,bleached transmittance rectified optical density(BTR density)and ion diffusion coefficient are boosted by~90% and over 15 times,respectively for TNF deposited with 150 cycles.A large number of self-doped Ti^(3+) defects and hydroxyl units together with order-disorder interconnections in the ALD TiO_(2) layer are responsible for the performance enhancement.The concept for successively evolving surface structure shares the feasibility of upgrading conventional ETMOs as well as designing new electrochromic materials.
基金partly supported by NSFC 11871092 and NSAF U1930402,ChinaPostdoctoral Science Foundation(Project No.2020M682895)a grant from the Research Grants Council of the Hong Kong Special Administrative Region,China(GRF Project No.Poly U15300920)。
文摘This article concerns the construction of high-order energy-decaying numerical methods for gradient flows of evolving surfaces with curvature-dependent energy functionals.The semidiscrete evolving surface finite element method is derived based on the calculus of variation of the semidiscrete surface energy functional.This makes the semidiscrete problem naturally inherit the energy decay structure.With this property,the semidiscrete problem is furthermore formulated as a gradient flow system of ODEs.The averaged vector-field collocation method is used for time discretization of the ODEs to preserve energy decay at the fully discrete level while achieving high-order accuracy in time.Extensive numerical examples are provided to illustrate the accuracy and energy diminishing property of the proposed method,as well as the effectiveness of the method in capturing singularities in the evolution of closed surfaces.
