A Facile in Situ and UV Printing Process for Bioinspired Self-Cleaning Surfaces

Abstract

A facile in situ and UV printing process was demonstrated to create self-cleaning synthetic replica of natural petals and leaves. The process relied on the spontaneous migration of a fluorinated acrylate surfactant (PFUA) within a low-shrinkage acrylated hyperbranched polymer (HBP) and its chemical immobilization at the polymer-air interface. Dilute concentrations of 1 wt. % PFUA saturated the polymer-air interface within 30 min, leading to a ten-fold increase of fluorine concentration at the surface compared with the initial bulk concentration and a water contact angle (WCA) of 108 • . A 200 ms flash of UV light was used to chemically crosslink the PFUA at the HBP surface prior to UV printing with a polydimethylsiloxane (PDMS) negative template of red and yellow rose petals and lotus leaves. This flash immobilization hindered the reverse migration of PFUA within the bulk HBP upon contacting the PDMS template, and enabled to produce texturized surfaces with WCA well above 108 • . The synthetic red rose petal was hydrophobic (WCA of 125 • ) and exhibited the adhesive petal effect. It was not superhydrophobic due to insufficient concentration of fluorine at its surface, a result of the very large increase of the surface of the printed texture. The synthetic yellow rose petal was quasi-superhydrophobic (WCA of 143 • , roll-off angle of 10 • ) and its self-cleaning ability was not good also due to lack of fluorine. The synthetic lotus leaf did not accurately replicate the intricate nanotubular crystal structures of the plant. In spite of this, the fluorine concentration at the surface was high enough and the leaf was superhydrophobic (WCA of 151 • , roll-off angle below 5 • ) and also featured self-cleaning properties.

Bio-Inspired Fluorine-Free Self-Cleaning Polymer Coatings

“…PDMSat contains only three units, which were not sufficient to impart a hydrophobic character. The dependence of wettability on the concentration and on the length of the apolar moiety of surface active comonomer has been already reported for fluorinated systems [17,31,32].…”

“…The WCA of the lotus and nasturtium leaves, reported in [26], respectively, due to seasonal factors. The surface of the fresh leaves was used as master and was replicated in the formulations using a UV-nanoimprint lithography process (UVNIL) and an intermediate negative polydimethylsiloxane mold (PDMS, SYLGARD™ 184, Dow, Midland, MI, USA) as detailed in [17]. This soft, vacuum-free and ambient molding technique preserves the delicate biological surfaces from damage and enables to accurately reproduce their nanometer scale features [27,28].…”

“…The present work follows up with the development of low-energy surfaces based on the spontaneous, enthalpy-driven migration of comonomers and resulting segregation at the polymer-air interface [12][13][14][15][16]. It is based on a highly scalable low-pressure, solvent-free, and ambient UV replication process of plant surfaces using a silicone template as demonstrated in a recent work [17]. In this study, one of the main challenges was the reverse migration of the fluorinated surfactant comonomer, from the polymer-air interface back to the bulk, upon contacting the low-surface energy silicone template, and suppression of the superhydrophobic properties.…”

A Self-Switchable Polymer Reactor for Controlled Catalytic Chemistry Processes with a Hyperbranched Structure

“…After being dispersed with sonication and nitrogen for 4 h, the encapsulated ionic silver was then reduced by an excess of sodium borohydride (tenfold, with regard to ionic nickel). The resulting polymer reactor was thoroughly washed with ethanol and water, and then dried under flowing nitrogen [ 16 ]. In this way, this novel HBP catalyst (i.e., AgHBP-A) was prepared.…”

A Rapid One-Step Process for Fabrication of Biomimetic Superhydrophobic Surfaces by Pulse Electrodeposition

“…Surface wettability is one of the most important properties of solid materials [ 1 , 2 ]. Superhydrophobic surfaces with a water contact angle (WCA) greater than 150° and a sliding angle less than 10° have attracted considerable attention due to their unique behavior for both fundamental research and industrial application in the field of self-cleaning [ 3 , 4 ], anti-icing [ 5 , 6 , 7 ], anti-corrosion [ 8 , 9 , 10 ], water-oil separation [ 11 ], etc. The superhydrophobic phenomenon can be attributed to a rough surface with special micro/nano structures and/or surface chemical composition with low surface free energy.…”