Bell‐Shaped Superhydrophilic–Superhydrophobic–Superhydrophilic Double Transformation on a pH‐Responsive Smart Surface

Abstract

Superhydrophobic to neutral water droplets, superhydrophilic to acidic or basic. This double transition of surface wettability in response to a single stimulus - pH - is demonstrated for the first time. The smart surface is composed of a rough gold surface modified with a self-assembled monolayer (SAM) containing three thiols, HS(CH2 )11 CH3 , HS(CH2 )10 COOH, and HS(CH2 )11 NH2 . A ternary diagram is generated that describes wettability as a function of the SAM composition and the pH of the surrounding solution.

A pH-responsive smart surface for the continuous separation of oil/water/oil ternary mixtures

“…In its current form, the hierarchical microand nanostructure of the millimeter-scale copper foam was sufficient to provide sufficient surface roughness for the fabrication of a pH-responsive smart surface presenting wettability transformation between superhydrophobicity/superhydrophilicity after further modification with mixed thiols of SH(CH 2 ) 9 CH 3 and SH(CH 2 ) 10 COOH at a molar ratio of 4:6. [29][30][31] The surface modification of the mixed thiols was confirmed through X-ray photoelectron spectroscopyspectra (Supplementary Figure S2). At the ratio of 4:6, the modified rough surface will exhibit superhydrophobicity under acidic conditions because the carboxylic acid groups are mostly protonated, and thus the methyl groups play a dominant role in surface wettability; under alkaline condition, the majority of carboxylic acid groups is deprotonated and hydrated, contributing to a superhydrophilic surface property.…”

Naked-eye point-of-care testing platform based on a pH-responsive superwetting surface: toward the non-invasive detection of glucose

“…To construct the superwetting surface, silica nanoparticles with different sizes (15,50, and 200 nm) were used to modify the surface topography ( Figure S1), promoting the roughness of hierarchical superwetting surfaces 14 . The organosilanes hydrophilic AEPTMS and hydrophobic OTMS were employed to functionalize the silica nanoparticles and switch the wettability as a function of the pH (Fig.…”

“…The highest peak at a binding energy of 532.0 eV corresponding to the O1 s peak illustrated the presence of abundant Si-O-Si group formed by the reaction of the organosilanes with the silica nanoparticles. A peak at approximately 103.6 eV, which is the Si2 p peak of SiO 2 , showed that there was little bare space on the silica nanoparticles 14,39 . These facts demonstrated that organosilanes were successfully grafted on the surface of the silica nanoparticles.…”

“…1a, AEPTMS and OTMS were important ingredients for achieving the pH response. AEPTMS has hydrophilic properties in acidic solutions due to the protonation of the pH-sensitive amino groups, and OTMS possesses superhydrophobic properties 14,39 . In the presence of a solution with a pH of 1, the surface was completely wetted within 1 s, and the CA was approximately 0°owing to the protonation of AEPTMS (Figure S3A and Movie S1).…”

“…Stimuli-responsive materials, which are functionally similar in wettability to natural surfaces, have been developed for bioseparation 4 , drug delivery systems 5,6 , cell-based diagnostics 7 , biosensing 8,9 , and so on 10,11 . By combining stimuli-responsive materials with microstructures or nanostructures, smart switching between superhydrophobic and superhydrophilic properties has been realized in the last two decades [12][13][14] . The current applications of superwettable materials, such as self-cleaning 15 , anti-icing 16 , water harvesting 17 , printing 18 , and water-oil separation 19 , are generally restricted to the industrial field because they need long-term operation processes, which might enhance the likelihood of damaging the functional surface by external forces 1 .…”