Dynamics of droplet impingement on bioinspired surface: insights into spreading, anomalous stickiness and break-up

Abstract

Inspired by the self-cleaning ability of lotus leaves and stickiness (towards water) of rose petals, we investigate the droplet impact dynamics on such bioinspired substrates. Impact studies are carried out with water droplets for a range of impact velocities on glass, PDMS and soft lithographically fabricated replicas of the lotus leaf and rose petals, which exhibit near identical wetting properties as that of the original biological entities. In this work, we investigate the spreading, dewetting and droplet break-up mechanisms subsequent to impact. Surprisingly, the rose petal and lotus leaf replicas manifest similar impact dynamics. The observation is extremely intriguing and counterintuitive, as rose petal and its replicas are sticky in contrast to lotus leaves. However, these observations are based on experiments performed with sessile water droplets. By contrast, in the current study, we find that rose petal replicas exhibit non-sticky behaviour at the short time scale ∼ ( O ( 10 − 3 ) ) s similar to that exhibited by lotus leaf replicas. Air entrapment in the micrometre features of bioinspired surfaces prevent frictional dissipation of droplet kinetic energy, leading to contact edge recession. We have also unveiled interesting universal physics that govern the spreading, recession of the contact edge and subsequent break-up modes (ligament or bulb-ligament) of the droplet.

Jet Dynamics Associated with Drop Impact on Micropillared Substrate

“…Bartolo [13] was one of the first researchers to report on these phenomena with findings that impact of the droplet on a superhydrophobic surface was found to cause a jet that possessed an axial velocity up to 40 times greater than the impact velocity of the droplet on the substrate. This jetting and droplet emission initiated from droplet impact on the hydrophobic surface has also been observed on many other surfaces, such as hydrophilic substrates [4], natural surfaces [14], razor blades [15], liquid surfaces [16], and oblique hydrophobic substrates [17], and, more recently, discovered to occur on fine mesh [18].…”

Nanometer-Thick Superhydrophobic Coating Renders Cloth Mask Potentially Effective against Aerosol-Driven Infections

“…The trajectory of the apex of the falling droplet was tracked and is depicted by the blue line in Figure b. The droplet was stuck into a low-energy “Cassie-impregnated Wenzel state” , due to the impact on the microprojections and secondary micro/nanofolds on the fabric surface. The droplet initially wetted the large micropits, but as the water could not penetrate further into the smaller micro/nanofolds, it created small air pockets.…”

Improved Mesenchymal Stem Cell Proliferation, Differentiation, Epithelial Transition, and Restrained Senescence on Hierarchically Patterned Porous Honey Silk Fibroin Scaffolds

“…Biomimetic Fabrication of Patterned Porous Honey/ Silk Fibroin Scaffolds. Patterned porous honey/silk fibroin scaffolds were fabricated by double replication of fresh rose petals using a soft lithography method (replica molding) 19,20 and subsequent lyophilization in a single step. At first, the PDMS stamp was made by replica molding on SYLGARD 184 (Dow Corning, USA) keeping the base to cross-linker ratio at 9:1 (w/w).…”