The evolution over time of wettability properties of super hydrophobic Al2024 developed using an IR-, ns-laser was studied under different storage conditions.

Ultrahydrophobic self cleaning surface is fabricated with nanosecond laser source on aluminium foil.

Micro-patterns with a single roughness were fabricated using a nanosecond laser source on stainless steel sheets to demonstrate a tunable and durable lotus effect via a vacuum process in a very short time interval. The wettability transitions of the vacuum processed μ-patterns were measured using the static water contact angle and found to be in the Cassie–Baxter state. The roll-off and static contact angle are 5° and 180°, respectively, for the μ-pillar and μ-channel structures. The surface exhibits bouncing and rolling of water droplets due to the composite interface. The transition of the wetting properties is a function of the vacuum process time and the minimum time required for the transition from ultrahydrophilic to ultrahydrophobic is found to be 15 minutes. The surface chemical analysis by XPS suggests that the chemisorption of hydrocarbon molecules onto hydroxylated metal oxide surfaces is much more effective under high vacuum than under an air atmosphere, due to the very low water vapor content inside the vacuum chamber, which avoids the passivation of reactive OH sites by hydrogen bonded water molecules. The wetting properties can be recycled by alternate plasma cleaning and vacuum processing of the laser-patterned surface.

This paper presents a novel structural piezoresistive pressure sensor with four-grooved membrane combined with rood beam to measure low pressure. In this investigation, the design, optimization, fabrication, and measurements of the sensor are involved. By analyzing the stress distribution and deflection of sensitive elements using finite element method, a novel structure featuring high concentrated stress profile (HCSP) and locally stiffened membrane (LSM) is built. Curve fittings of the mechanical stress and deflection based on FEM simulation results are performed to establish the relationship between mechanical performance and structure dimension. A combination of FEM and curve fitting method is carried out to determine the structural dimensions. The optimized sensor chip is fabricated on a SOI wafer by traditional MEMS bulk-micromachining and anodic bonding technology. When the applied pressure is 1 psi, the sensor achieves a sensitivity of 30.9 mV/V/psi, a pressure nonlinearity of 0.21% FSS and an accuracy of 0.30%, and thereby the contradiction between sensitivity and linearity is alleviated. In terms of size, accuracy and high temperature characteristic, the proposed sensor is a proper choice for measuring pressure of less than 1 psi.

In this paper, we introduce a method to efficiently use a high-energy pulsed 1.7 ps HiLASE Perla laser system for two beam interference patterning. The newly developed method of large-beam interference patterning permits the production of micro and sub-micron sized features on a treated surface with increased processing throughputs by enlarging the interference area. The limits for beam enlarging are explained and calculated for the used laser source. The formation of a variety of surface micro and nanostructures and their combinations are reported on stainless steel, invar, and tungsten with the maximum fabrication speed of 206 cm²/min. The wettability of selected hierarchical structures combining interference patterns with 2.6 µm periodicity and the nanoscale surface structures on top were analyzed showing superhydrophobic behavior with contact angles of 164°, 156°, and 150° in the case of stainless steel, invar, and tungsten, respectively.