micro-, nano- and hierarchical structures for superhydrophobicity, self-cleaning and low adhesion by...

Micro-, nano- and hierarchical structures for superhydrophobicity, self-cleaning and low adhesion

by Bharat Bhushan, Yong Chae Jung, and Kerstin Koch

Philosophical Transactions AVolume 367(1894):1631-1672

May 13, 2009

©2009 by The Royal Society

A schematic of condensed water vapour from the environment forming meniscus bridges at asperity contacts that lead to an intrinsic attractive force.

Bharat Bhushan et al. Phil. Trans. R. Soc. A 2009;367:1631-1672


(a) SEM images (shown at three magnifications (i)–(iii)) of lotus (N. nucifera) leaf surface, which consists of a microstructure formed by papillose epidermal cells covered with three-dimensional

epicuticular wax tubules on the surface, which create nanostr...



(a) Schematic of a liquid droplet in contact with (i) a smooth solid surface (contact angle, θ0) and (ii) a rough solid surface (contact angle, θ), (b) contact angle for a rough surface (θ) as a function

of the roughness factor (Rf) for various contact angl...



(a) Schematic of the formation of a composite solid–liquid–air interface for a rough surface and (b) fLA requirement for a hydrophilic surface to become hydrophobic as a function of the

roughness factor (Rf) and θ0 (Jung & Bhushan 2006).



Tilted surface profile (tilt angle, α) with a liquid droplet; advancing and receding contact angles are θadv and θrec, respectively.



Schematic of the structure of an ideal hierarchical surface.



SEM images of (a) the two nanopatterned polymer surfaces (shown using two magnifications to show both the asperity shape and the asperity pattern on the surface; (i)(ii) PMMA low aspect

ratio (LAR) and (iii)(iv) PMMA high aspect ratio (HAR)) and (b) the mic...



Contact angles for various patterned surfaces on (a) PMMA and (b) PS polymers and values calculated using the Wenzel equation (Jung & Bhushan 2006).



(a) Surface height maps of the patterned Si surface (5 μm diameter, 10 μm height, 10 μm pitch pillars) using an optical profiler (Bhushan & Jung 2007) and (b) a liquid droplet suspended on a

hydrophobic surface consisting of a regular array of circular pill...



(a) Static contact angle (circles; the dotted line represents the transition criterion range obtained using equation (3.1)) and (b) contact angle hysteresis (circles) and tilt angle (triangles) as a

function of pitch values for patterned surfaces (5 μm diam...



(a) Evaporation of a droplet on a patterned surface.



(a) Snapshots of a droplet with 1 mm radius hitting a patterned surface.



(a) Schematic of the two-step moulding process used to fabricate microstructure, in which at first (i) a negative is generated and then (ii) a positive.



Schematic of the thermal evaporation system for self-assembly of a wax.



Schematic of the glass recrystallization chamber used for wax tubule formation.



SEM images of the morphology of lotus wax deposited on the flat epoxy replica surface after two treatments of specimens measured at 45° tilt angle: (a) after 7 days at 21°C, nanostructure on flat

epoxy replica was found with no tubules; and (b) after 7 days...



(a) SEM images of the flat surface and nanostructures fabricated with various masses of n-hexatriacontane on epoxy resin measured at 45° tilt angle (shown using two magnifications; (i)(ii)

flat, (iii)(iv) nanostructure (0.12 μg mm−2), (v)(vi) nanostructure ...



(a) (i)–(iii) Bar charts showing the measured static contact angle, contact angle hysteresis and tilt angle, calculated contact angles obtained using Wenzel and Cassie–Baxter equations with a

given value of θ0, and calculated contact angle hysteresis using ...



SEM images of (a) the flat surface, (b) nanostructure, (c) microstructure and (d) hierarchical structure measured at 45° tilt angle (shown using two magnifications (i)(ii)).



(a)–(c) Bar charts showing the measured static contact angle, contact angle hysteresis and tilt angle, calculated contact angles obtained using Wenzel and Cassie–Baxter equations with a

given value of θ0, and calculated contact angle hysteresis using the Ca...



Evaporation of a droplet on (a) microstructured and (b) hierarchical structured surfaces.



The remaining dust trace after droplet evaporation on (a) the microstructured and (b) the hierarchical structured surfaces.



(a) SEM images taken at 45° tilt angle (shown using two magnifications) of the (i–iv) nanostructure and (v–viii) hierarchical structure fabricated with two different masses ((i)(ii) and

(v)(vi) 0.6 and (iii)(iv) and (vii)(viii) 0.8 μg mm−2) of T. majus wax ...



(a) (i)–(iii) Bar charts showing the measured static contact angle, contact angle hysteresis and tilt angle on various structures fabricated with 0.8 μm mm−2 mass of T. majus wax after storage at

50°C with ethanol vapour.



SEM images taken at 45° tilt angle (shown using three magnifications) of (a(i–iii)) nanostructure on flat replica, (b(i–iii)) microstructures in lotus replica and (iv–vi) micropatterned Si replica and

(c(i–iii)) hierarchical structure using lotus replica an...



(a)–(c) Bar charts showing the measured static contact angle, contact angle hysteresis and tilt angle on various structures fabricated with 0.8 μg mm−2 mass of lotus wax after storage at 50°C

for 7 days with ethanol vapour.



Bar chart showing the remaining particles after self-cleaning experiments applying droplets with nearly zero kinetic energy on various structures fabricated from lotus wax using 1–10 and 10–15

μm SiC particles.



Schematic showing wetting of the four different surfaces fabricated.



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