Fabrication of “Roll-off” and “Sticky” Superhydrophobic Cellulose Surfaces via Plasma Processing

Abstract

Most of the artificial superhydrophobic surfaces that have been fabricated to date are not biodegradable, renewable, or mechanically flexible and are often expensive, which limits their potential applications. In contrast, cellulose, a biodegradable, renewable, flexible, inexpensive, biopolymer which is abundantly present in nature, satisfies all the above requirements, but it is not superhydrophobic. Superhydrophobicity on cellulose paper was obtained by domain-selective etching of amorphous portions of the cellulose in an oxygen plasma and subsequently coating the etched surface with a thin fluorocarbon film deposited via plasma-enhanced chemical vapor deposition using pentafluoroethane as a precursor. Variation of plasma treatment yielded two types of superhydrophobicity : "roll-off" (contact angle (CA), 166.7 degrees +/- 0.9 degrees ; CA hysteresis, 3.4 degrees +/- 0.1 degrees ) and "sticky" (CA, 144.8 degrees +/- 5.7 degrees ; CA hysteresis, 79.1 degrees +/- 15.8 degrees ) near superhydrophobicity. The nanometer scale roughness obtained by delineating the internal roughness of each fiber and the micrometer scale roughness which is inherent to a cellulose paper surface are robust when compared to roughened structures created by traditional polymer grafting, nanoparticle deposition, or other artificial means.

Superhydrophobic Paper in the Development of Disposable Labware and Lab-on-Paper Devices

“…The effect of water immersion with time was investigated, using 9 time points (1,6,12,24, and 48 h, and 1, 2, 3, and 4 weeks). During the first two weeks no significant changes were detected on the WCA value of the SH surface.…”

“…25 The SH paper may bring new strengths on the development of lab-on-paper (LOP) devices: the increase in the wettability contrasts between wettable and repellent regions, the prevention of water and moisture absorption, and the avoidance of pathogenic contamination. [22][23][24]26 This work proposes different methods to pattern flat SH paper surfaces creating wettable domains that contrast with the superhydrophobic behavior of the remaining area.…”

Preparation of superhydrophobic cauliflower-like silica nanospheres with tunable water adhesion

“…[20][21][22][23][24] Contrary to this characteristic a new kind of sticky superhydrophobic material with high water adhesion has recently been reported and attracted people's attention. [25][26][27][28] On this surface the contact angle of the water droplet is usually above 150 , while this surface also possesses a sufficiently high adhesive force to the liquid at the same time. As a result, the water droplet would be stuck and would not roll off even with the surface upside down.…”

“…The research succeeding in fabricating superhydrophobic surfaces with tunable water adhesion are mostly based on the physical technique -surface nanostructure construction. 27,[36][37][38] Recently, a sticky superhydrophobic surface was innovatively fabricated via introducing hydrophobic and hydrophilic nanodomains on a microscale rough surface, and the adhesive force could be tuned by adjusting the ratio of the hydrophilic and hydrophobic domains. 39,40 Under our basis of surface hydrophilicity/hydrophobicity construction, 41,42 herein, we report a very simple method to synthesize cauliflower-like silica nanospheres via a one-step introduction of organic groups.…”

Phenomenological model of wetting charged dielectric surfaces and its testing with plasma-treated polymer films and inflatable balloons

“…Electrical charging of polymers takes place under plasma treatment (at low and atmosphericpressure), which is widely used for the modification of surface properties of solid organic materials [10][11][12][13][14][15][16]. The plasma treatment creates a complex mixture of surface functionalities which influence surface physical and chemical properties; this results in a dramatic change in the wetting behaviour of the surface [16][17][18][19][20][21][22].…”