Superhydrophobic structures on 316L stainless steel surfaces machined by nanosecond pulsed laser

Abstract

In this paper nanosecond laser machining process was developed to improve the hydrophobicity of AISI 316L stainless steel surface. A geometrical model of laser machined Gaussian micro hole, together with constrain conditions, was established for the first time to predict surface contact angle and optimize structure geometries for maximizing its hydrophobicity. The effects of processing laser power and pitch of microstructures on the topography of the machined surface were investigated through laser machining experiment. Subsequently, the water droplet contact angle was measured to evaluate the hydrophobicity of different specimens. Results show that under the laser power of 10 W and 14 W, with the increase of the pitch of microstructures, the contact angle increases until it reaches its peak value then drops gradually. Under the large pitch of microstructure, the contact angle will increase with the increase of the processing laser power. Under the same pitch of microstructure, the contact angle will increase with the increase of ten-point height of surface topography, Sz which is a better parameter than Sa (arithmetical mean height) to characterise hydrophobicity of surface with Gaussian holes. This study shows that large Sz is an essential condition to form the stable and robust Cassie–Baxter state, i.e. a condition to achieve superhydrophobicity. The comparison between the predicted and measured contact angles in experiments shows that the proposed model can accurately predict contact angle and optimize the geometries of the microstructure to achieve maximum hydrophobicity

Approaches for Evaluating and Engineering Resilient Superhydrophobic Materials

“…The dual-scale roughness of many superhydrophobic surfaces can be exploited to generate bulkier protective features (Figure 10) [93,80]. The principle behind this approach is to utilise larger, more resilience morphological features to act as the sacrificial points of contact when handled manually.…”

Design and Fabrication of Dual-Scale Broadband Antireflective Structures on Metal Surfaces by Using Nanosecond and Femtosecond Lasers

“…Periodic black silicon antireflection surface structures were fabricated using four-beam laser interference lithography and studied [25]. In general, nanosecond pulsed lasers have proved to be a reliable tool for achieving ultralow reflectance due to their high processing efficiency and low cost [26,27]. Boinocivh et al used a nanosecond laser to induce regular microgrooves by covering titanium alloy surfaces with porous nanostructures, and the modified surfaces were superior in terms of both corrosion and wear resistance [28].…”

Preparation of Superhydrophobic Surface on Titanium Alloy via Micro-Milling, Anodic Oxidation and Fluorination

“…Superhydrophobic surfaces were the surfaces with a water contact angle (CA) above 150 • and a contact angle hysteresis below 5 • . Materials with superhydrophobic surface show great potential, and have been widely applied in the field of biomedical materials, especially for cardiovascular stent materials, due to their unique characteristics, such as self-cleaning, low adhesion and reduced viscosity resistance [6][7][8][9][10]. For instance, it has been reported that superhydrophobic surfaces could hinder the adhesion of bacteria to surface so as to reduce the risk of instrument and implant infections [11].…”