Rationally Designed, Multifunctional Self-Assembled Nanoparticles for Covalently Networked, Flexible and Self-Healable Superhydrophobic Composite Films

Structure-Property Relationships for Fluorinated and Fluorine-Free Superhydrophobic Crack-Free Coatings

In this study, particle loading, polyfluorinated alkyl silanes (PFAS or FAS) content, superhydrophobicity, and crack formation for nanocomposite coatings created by the spray coating process were investigated. The formulations comprised hydrophobic silica, epoxy resin, and fluorine-free or FAS constituents. The effect of FAS content and FAS-free compositions on the silica and epoxy coatings' chemistry, topography, and wetting properties was also studied. All higher particle loadings (~30 wt.%) showed superhydrophobicity, while lower particle loading formulations did not show superhydrophobic behavior until 13% wt. FAS content. The improved water repellency of coatings with increased FAS (low particle loadings) was attributed to a combination of chemistry and topography as described by the Cassie state. X-ray photoelectron spectroscopy (XPS) spectra showed fluorine enrichment on the coating surface, which increases the intrinsic contact angle. However, increasing the wt.% of FAS in the final coating resulted in severe crack formation for higher particle loadings (~30 wt.%). The results show that fluorine-free and crack-free coatings exhibiting superhydrophobicity can be created.

Highly Effective and Efficient Self-Assembled Multilayer-Based Electrode Passivation for Operationally Stable and Reproducible Electrolyte-Gated Transistor Biosensors

To ensure the operational stability of transistor-based biosensors in aqueous electrolytes during multiple measurements, effective electrode passivation is crucially important for reliable and reproducible device performances. This paper presents a highly effective and efficient electrode passivation method using a facile solution-processed self-assembled multilayer (SAML) with excellent insulation property to achieve operational stability and reproducibility of electrolyte-gated transistor (EGT) biosensors. The SAML is created by the consecutive self-assembly of three different molecular layers of 1,10-decanedithiol, vinyl-polyhedral oligomeric silsesquioxane, and 1-octadecanethiol. This passivation enables EGT to operate stably in phosphate-buffered saline (PBS) during repeated measurements over multiple cycles without short-circuiting. The SAML-passivated EGT biosensor is fabricated with a solution-processed In2O3 thin film as an amorphous oxide semiconductor working both as a semiconducting channel in the transistor and as a functionalizable biological interface for a bioreceptor. The SAML-passivated EGT including In2O3 thin film is demonstrated for the detection of Tau protein as a biomarker of Alzheimer's disease while employing a Tau-specific DNA aptamer as a bioreceptor and a PBS solution with a low ionic strength to diminish the charge-screening (Debye length) effect. The SAML-passivated EGT biosensor functionalized with the Tau-specific DNA aptamer exhibits ultrasensitive, quantitative, and reliable detection of Tau protein from 1 × 10-15 to 1 × 10-10 M, covering a much larger range than clinical needs, via changes in different transistor parameters. Therefore, the SAML-based passivation method can be effectively and efficiently utilized for operationally stable and reproducible transistor-based biosensors. Furthermore, this presented strategy can be extensively adapted for advanced biomedical devices and bioelectronics in aqueous or physiological environments.

Superhydrophobic materials used for anti-icing Theory, application, and development

The accumulation of ice will reduce the performance of the base material and lead to all kinds of damage, even a threat to people's life safety. Recent increasing studies suggest that superhydrophobic surfaces (SHSs) originating from nature can remove impacting and condensing droplets from the surface before freezing to subzero temperatures, and it can be seen that hydrophobic/SH coating has good freezing cold resistance. But such anti-icing performances and developments in practical applications are restricted by various factors. In this paper, the mechanism and process of surface icing phenomenon are introduced, as well as how to prevent surface icing on SHS. The development of SH materials in the aspect of anti-icing in recent years is described, and the existing problems in the aspect of anti-icing are analyzed, hoping to provide new research ideas and methods for the research of anti-icing materials.

Transparent and Flexible Amphiphobic Coatings with Excellent Fold Resistance via Solvent-Free Coating and Photocuring of Fluorinated Liquid Nitrile-Butadiene Rubber

Amphiphobic surfaces have been developed for various applications. However, the harsh construction conditions and multistep processes limit their practical application. Especially for those with a particular surface roughness and morphology, the amphiphobic property might provide a slight deformation. Here, a facile large-area construction of transparent and flexible amphiphobic coatings with excellent fold resistance has been established by simple casting of the fluorinated liquid nitrile-butadiene rubber (F-LNBR) followed by solvent-free photocuring. It was found that the fluorocarbon groups could concentrate onto the coating surface during the UV-induced photocuring. With a certain coating amount, a stable oleophobic coating was achieved with static contact angles of about 95° and 111° for nonpolar oil (n-hexadecane) and polar oil (diiodomethane). Most importantly, the static contact angles of water and diiodomethane of the amphiphobic coatings on the iron sheet increased after bending and remained around 131° and 120° after being completely folded in half for 100 cycles because the inner fluorocarbon groups could be squeezed out from the flexible cross-linked rubber matrix as a reservoir. Such features indicated the promising self-cleaning and surface protection of the proposed transparent and flexible amphiphobic coatings for deformable substrates.

Single Tungsten Atom-Modified Cotton Fabrics for Visible-Light-Driven Photocatalytic Degradation and Antibacterial Activity

Various single-atom materials exhibit distinguished performances in catalysis and biology. To boost their applications, single-atom-based strategies are highly demanded to exhibit repeatable functions on advanced wearable substrates. However, single-atom approaches are rarely reported to anchor on wearable materials, i.e., widely applied cotton fabrics. Here, we developed a simple method of loading uniformly dispersed single tungsten atoms on cotton via ordinary direct-dye processing to exhibit superior sustainable functions. The single sites of tungsten atom centers are constructed by binding oxygen-coordinated single tungsten atom on the cotton fabric surface via -COOH groups. Consequently, the band gap of single sites decreases significantly to 2.75 from 3.03 eV. Therefore, the single-site-modified cotton exhibits excellent visible-light-driven (>420 nm) photocatalytic degradation efficiency of organic dyes, which exceeds other reported cotton-based materials by nearly two orders of magnitude. Furthermore, the single-site-modified cotton also exhibits great antibacterial performance due to reactive oxygen species. Moreover, the cotton with anchored single sites possesses great washing-resistance ability during 20 laundry cycles under soap-washing conditions. After recycling, the single sites on cotton have no obvious changes in the microstructure, which demonstrates the success of our sustainable strategy of single sites anchored on cotton. The single-site technique can be extended to many other elemental atoms on various wearable devices, providing a playground for functional material communities.

Fast Healable Superhydrophobic Material

Self-healability is a crucial feature for developing artificial superhydrophobic surfaces. Although self-healing of microscopic defects has been reported, the restoration of severely damaged superhydrophobic surfaces remains a technological challenge. Here, we report a robust superhydrophobic surface possessing ultrafast recoverability after catastrophic damage. The surface is fabricated via integrating its hierarchical texture comprised of Super P (a conductive carbon black) and TiO₂ nanoparticles into a poly(dimethylsiloxane) network cross-linked by dynamic pyrogallol-Fe coordination. In the presence of an electrical trigger, the surface restores its macroscopic configuration, hierarchical texture, mechanical properties, and wettability within 1 min after being cut or plasma etching. The restoration is attributed to the reconstruction of the multiscale structures through dynamic coordination. Application of the self-healable surface is demonstrated by a fast de-icing process. The present investigation offers a novel insight into the durability and reliability of artificial superhydrophobic surfaces against catastrophic damage, which has potential application in the fields including self-cleaning, anti-icing, advanced electronics, and so on.