Droplet Impact Dynamics on Biomimetic Replica of Yellow Rose Petals: Rebound to Micropinning Transition

Abstract

Rose petals exhibit a phenomenal wetting property of being sticky and superhydrophobic simultaneously. A recent study has shown that for short timescales, associated with drop impact phenomenon, lotus leaf and rose petal replicas exhibit similar wettability, thereby highlighting the difference between long and short time wettability. Also, short time wetting on rose petals of different colors remains completely unaddressed, as almost all existing study on wetting of rose petals have been performed with the classical red rose (Rosa chinensis). In this paper, we compare the drop impact studies on replicas of a yellow rose petal, with those on extensively studied red rose petal replicas and the lotus leaf over a wide range of Weber number (We), by varying the height of fall (h) from 10 to 375 mm. Our results reveal that over the replica of a yellow rose petal, the initial impact outcome varies from complete rebound to micro pinning and eventually complete pinning depending on the kinetic energy of the impacting drop, in contrast to that on red rose petal replica on which the droplet always pinned. Based on experimental finding, we present a comprehensive regime phase map of the post impact behavior of the drop on different surfaces as a function of impact height. We also present a simple scaling analysis to understand the combined effect of pattern height and periodicity on the critical h corresponding to wetting regime transition. Additionally, variation of maximum spreading diameter and spreading time with the h for the different surfaces is also discussed. The results highlight that the initial impact dynamics of a water drop over a topographically patterned substrate is a strong function of the topographical parameters and can be very different from the equilibrium wetting state.

Water-repelling behavior of the 1-D hematite nano-network

“…Such a surface may behave like an “adhesive Cassie”-type surface. 68,69 The water contact angle on the irradiated surface was calculated theoretically using the Cassie model by considering the average pore diameter of 50 nm (Fig. 1(c)) and a thickness of 1.01 μm for the nano-network, yielding a contact angle of about 92°, which is within the range of observed angles in Fig.…”

Fundamentals and Applications of Surface Wetting

“…Many studies have reported on fabricating artificial microtextured surfaces mimicking nature. The outcomes of droplet impact on these surfaces are also reported, such as recent studies mimicking taro leaf and yellow rose petals . The dynamic behavior of the impacting droplet depends on the droplet’s initial We and the microtexture shape and size of the surface.…”

Universality of Scaling Laws Governing Contact and Spreading Time Spans of Bouncing Liquid Marbles and its Physical Origin

“…Bouncing of droplets gives rise to an amazing diversity of physical events. − A broad range of physical phenomena is associated with the flow in the drop, initiated by its impact onto a solid substrate. − The scenarios of drop impact depend on the impact velocity, its direction relative to the surface, the drop radius, the physical properties of the liquid (its density, surface tension, viscosity, and viscoelasticity), − the topography of the surface and its wettability, ,, isothermal effects, and air entrapment . Droplet impact plays a key role in a variety of technological situations, including the building industry, development of anti-icing surfaces, painting/coating, spray technology, corrosion of turbine blades and aircraft, oil separation, heat transfer, and electricity generation. , Naturally occurring impact of rain droplets with leaves and soil is also of great interest. , Rapid progress in understanding the complicated interplay of processes occurring during droplet impact came with the development of rapid imaging experimental techniques …”