Laser-Assisted Structures for Efficient Fluid Management on Stainless Steel Surfaces.

The article presents a high-productivity laser-structuring method combined with a hydrophobic post-treatment to create zone-structured surfaces with a decreasing wetting angle on AISI 304 stainless steel surfaces. We have investigated the impact of laser processing modes and hydrophobic substances on wetting and hysteresis angles and successfully demonstrated autonomous droplet movement over this zone-structured surface. A critical condition for autonomous fluid flow is the need for the drop to touch the boundary between the two zones. This can be achieved by settling the droplet directly on the boundary of the two zones or by using droplets whose surface contact diameter is on the order of magnitude or higher than the zone size. The zone-structured surface showed reusability, maintaining its properties even after 30 droplet passages. The zone-structured surfaces with a decreasing wetting angle can be used for moving a droplet along a complex trajectory as well as for mixing various liquids.

Nanoscale investigations of femtosecond laser induced nanogratings in optical glasses.

Femtosecond (fs) laser irradiation inside transparent materials has drawn considerable interest over the past two decades. More specifically, self-assembled nanogratings, induced by fs laser direct writing (FLDW) inside glass, enable a broad range of potential applications in optics, photonics, or microfluidics. In this work, a comprehensive study of nanogratings formed inside fused silica by FLDW is presented based on high-resolution electron microscopy imaging techniques. These nanoscale investigations reveal that the intrinsic structure of nanogratings is composed of oblate nanopores, shaped into nanoplanes, regularly spaced and oriented perpendicularly to the laser polarization. These nanoporous layers are forced-organized by light, resulting in a pseudo-organized spacing at the sub-wavelength scale, and observed in a wide range of optical glasses. In light of the current state of the art, we discuss the imprinting of nanoporous layers under thermomechanical effects induced by a plasma-mediated nanocavitation process.

Impact of Glass Free Volume on Femtosecond Laser-Written Nanograting Formation in Silica Glass.

In this study, we investigate the effects of densification through high pressure and temperature (up to 5 GPa, 1000 °C) in the making of nanogratings in pure silica glass, inscribed with femtosecond laser. The latter were monitored through retardance measurements using polarized optical microscopy, and their internal structure was observed under scanning electron microscopy. We reveal the difficulty in making nanogratings in densified silica glasses. Based on this observation, we propose that free volume may be a key precursor to initiate nanograting formation.

Eco-friendly Approach for Creation of Resonant Silicon Nanoparticle Colloids.

The commercial application of Mie-resonant nanophotonic technologies currently used in various laboratory studies, from biosensing to quantum optics, appears to be challenging. Development of colloidal-based fabrication approaches is a solution to face the issue. In our research, we studied the fabrication of resonant Si nanoparticle (NP) arrays on a surface with controlled wettability. First, we use nanosecond (ns) laser ablation in water and subsequent density gradient separation to obtain colloids of resonant spherical crystalline silicon NPs with a low polydispersity index. Then, the same industrial ns laser is applied to create a wetting gradient on the steel substrate to initiate a self-assembly of the NPs deposited by drop casting. Thus, we use a single commercial ns laser for producing both the NPs and the hydrophilic wetting gradient. We apply an easily operating size separation technique and only non-toxic media. This research contributes to the large-scale fabrication of various optical devices based on resonant high-refractive index nanostructures by ecologically friendly self-assembly techniques.

Laser-Induced µ-Rooms for Osteocytes on Implant Surface: An In Vivo Study.

Laser processing of dental implant surfaces is becoming a more widespread replacement for classical techniques due to its undeniable advantages, including control of oxide formation and structure and surface relief at the microscale. Thus, using a laser, we created several biomimetic topographies of various shapes on the surface of titanium screw-shaped implants to research their success and survival rates. A distinctive feature of the topographies is the presence of "µ-rooms", which are special spaces created by the depressions and elevations and are analogous to the µ-sized room in which the osteocyte will potentially live. We conducted the comparable in vivo study using dental implants with continuous (G-topography with µ-canals), discrete (S-topography with µ-cavities), and irregular (I-topography) laser-induced topographies. A histological analysis performed with the statistical method (with p-value less than 0.05) was conducted, which showed that G-topography had the highest BIC parameter and contained the highest number of mature osteocytes, indicating the best secondary stability and osseointegration.