Azeotropic Binary Solvent System Containing Nonfluorinated Polymer-Grafted Silica Nanoparticles for the Fabrication of a Superhydrophobic Surface.

This study describes a method for fabricating a superhydrophobic surface on glass via a colloidal deposition technique based on solvent evaporation-induced aggregation. Silica nanoparticles with a low grafting density of long-chain poly(cyclohexyl methacrylate) (PCH) were dispersed in a binary solvent system consisting of tetrahydrofuran (THF) and methanol (MeOH) with an azeotropic point and the nonfluorinated and hydrophobic PCHMA having a solubility parameter similar to that of THF. In the early stages of evaporation, the binary mixtures tend to induce the aggregation of PCH-NP due to the azeotropic point of the solvent components, leading to the formation of surface structures ranging from smooth to rough on the substrate. By adjusting the initial ratio of the binary solvents, a superhydrophobic coating with a water contact angle of 154 ± 2° and a sliding angle of less than 10° was achieved at a THF content of 60 wt %. This facile approach using azeotropes successfully shows that changes in the solvent composition of the binary solvent system during evaporation can be used to prepare superhydrophobic coatings with well-controlled surface structures.

Femtosecond Laser-Induced Periodic Surface Structures on Different Tilted Metal Surfaces.

Laser-induced periodic surface structures (LIPSS) are used for the precision surface treatment of 3D components. However, with LIPSS, the non-normal incident angle between the irradiated laser beam and the specimen surface occurs. This study investigated LIPSS on four different metals (SUS 304, Ti, Al, and Cu), processed on a tilted surface by an s-polarized femtosecond fiber laser. A rotated low spatial frequency LIPSS (LSFL) was obtained on SUS 304 and Ti materials by the line scanning process. However, LSFL on Cu and Al materials was still perpendicular to the laser polarization. The reason for the rotated and un-rotated LSFL on tilted metal surfaces was presented. The electron-phonon coupling factor and thermal conductivity properties might induce rotational LSFL on tilted SUS 304 and Ti surfaces. When fabricating LSFL on an inclined plane, a calibration model between the LSFL orientation and inclined plane angle must be established. Hence, the laser polarization direction must be controlled to obtain suitable LSFL characteristics on a 3D surface.

Two-Dimensional Periodic Nanostructure Fabricated on Titanium by Femtosecond Green Laser.

Laser-induced periodic surface structures (LIPSS) is the sub-wavelength periodic nanostructure, which is generally generated by the femtosecond laser. There are two kinds of LIPSS, low spatial frequency LIPSS (LSFL) and high spatial LIPSS (HSFL), and the period size is close and less than half of the laser wavelength, respectively. Fabrication of two-dimensional (2D) LSFL and HSFL on a titanium surface with a linear-polarized femtosecond green laser beam (wavelength 515 nm) and cross-scanning strategies is demonstrated in this study. Four types of LIPSS structures are obtained by controlling the laser fluence, irradiated pulses, and cross-scanning strategies: 1D-LSFL perpendicular to laser polarization with a period of 300-360 nm, 1D-HSFL parallel to laser polarization with a period of 55-75 nm, 2D-LSFL dot-like structures with a period ~200 nm, and 2D-HSFL net-like structures with a period of 50-100 nm.

Effect of Size-Dependent Photodestructive Efficacy by Gold Nanomaterials with Multiphoton Laser.

The photostability, photodestructive efficacy, two-photon excitation cross section, and two-photon fluorescence of gold nanoparticles conjugated with a hydrophilic photosensitizer, indocyanine green, via multiphoton laser exhibited an increased size effect in methicillin-resistant Staphylococcus aureus and A549 cancer cells that was dependent on the size of multifunctional gold nanomaterials, but the effect only occurred when nanomaterials within 100 nm in diameter were used. Besides, the enhanced effectiveness of photodestruction, photostability, and contrast probe indicated an additive effect in the therapeutic and imaging efficiency of multifunctional gold nanomaterials. Consequently, the preparation of the multifunctional gold nanomaterials and their use in biomedical applications via multiphoton laser is an alternative and potential therapeutic approach for killing bacteria and for ablating cancer cells.