Recent Progresses in Super-Hydrophobicity and Micro-Texturing for Engineering Applications

Increasing interests have been prevalent lately among the research fraternity for the development of superhydrophobic surfaces considering the favorable properties exuded by them. Recently, anti-microbial superhydrophobic coatings have been employed effectively in anti-biofouling, corrosion resistance, and self-cleaning, anti-reflecting coating, biomedical and cavitation erosion applications. Further, patterned topology by micro/nano surface texturing has been perceived as an engineering opportunity to enhance the surface performance and has opened various avenues for exploration. This work reports the recent research findings pertaining to the concept of superhydrophobicity and micro-texturing particularly in the context of their application for the impediment of corrosion in submerged components. The comprehensive review on superhydrophobic surfaces and micro-texturing suggests that the integrated application of these surface modification techniques for mechanical interlocking of deposited coating.

Granular Media Friction Pad for Robot Shoes—Hexagon Patterning Enhances Friction on Wet Surfaces

For maximizing friction forces of the robotic legs on an unknown/unpredictable substrate, we introduced the granular media friction pad, consisting of a thin elastic membrane encasing loosely filled granular material. On coming into contact with a substrate, the fluid-like granular material flows around the substrate asperities and achieves large contact areas with the substrate. Upon applying load, the granular material undergoes the jamming transition, rigidifies and becomes solid-like. High friction forces are generated by mechanical interlocking on rough substrates, internal friction of the granular media and by the enhanced contact area caused by the deformation of the membrane. This system can adapt to a large variety of dry substrate topologies. To further increase its performance on moist or wet substrates, we adapted the granular media friction pad by structuring the outside of the membrane with a 3D hexagonal pattern. This results in a significant increase in friction under lubricated conditions, thus greatly increasing the universal applicability of the granular media friction pad for a multitude of environments.

PEEK as a Potential Material for Dental Implants and its Biomechanical Properties and Osteoblast Cell Response

Proper osseointegration is crucial for the success of dental and orthopedic implants. Titanium-6Aluminum-4Vanadium (TAV) is one of the most popular implant materials; however, polyetheretherketone (PEEK) has gained the interest of implant researchers and manufacturers over the past several years due to its lower modulus of elasticity compared to metallic implant materials. Porosity and patterned surface morphologies are thought to improve mechanical interlocking and play an important role in the differentiation of pre-osteoblasts into mature osteoblasts. This study aimed to determine the effects a macro patterned PEEK surface has on the material’s mechanical properties and the proliferation, differentiation, and maturation of pre-osteoblasts. Mechanical testing data indicated that the macro patterning improved the mechanical interlocking and has no detrimental effect on compression strength. DNA data and live/dead imaging showed that pre-osteoblasts on solid PEEK specimens did not readily differentiate but instead encouraged proliferation only. However, ALP data in comparison to the DNA data showed that cells on patterned PEEK specimens more readily entered the differentiation pathway to mineralization. This is further confirmed by the patterned PEEK specimens showing an overall higher amount of cell mineralization. Clinical significance: This study concludes that surface macro patterning of PEEK material increases the mechanical interlocking and enhances the osseointegration capability without diminishing mechanical properties.

Sustainable Biocomposites Produced From Cotton Stalk Wastes: Effect of Heat Treatment

The novelty of this study is to explore the effect of heat treatment of CS on the properties of biocomposites. 200°C, 300°C, 500°C, and burning of 500°C were selected to heat treat CS to obtain CS fillers, and the biocomposites were prepared using CS fillers and LLDPE. The heat treatment of CS can improve the interface bonding and compatibility of biocomposites by the results of FTIR, SEM, and CA. The crystal planes were not changed by the addition of CS fillers. The heat treatment of CS promoted crystallization, improved the heat resistance of LLDPE. In addition, the flexural properties, tensile properties, stiffness, elasticity, creep resistance and, stress relaxation resistance were all increased by the heat treatment of CS, although it exhibits an adverse effect on the impact strength of LLDPE. The best flexural properties (13.00 MPa and 0.75 GPa) were obtained in 200CSB-L due to the enhancement of CS rigidity by 200°C heat treatment, and the best tensile properties (10.89 MPa and 0.26 GPa) were obtained in 500CSB-L due to its mechanical interlocking structure. The results of this study indicate that heat treatment will play an important role in biocomposites in terms of the benefit in mechanical properties.

Effect of Agro Waste Saline Treated Cellulose Nanofiller on Mechanical, Visco Elastic and Thermal Behaviour of Epoxy Nanocomposites

A comparably novel strategy to develop sustainable nano composites is presented, in which cellulose nano fibers (CNFs) reinforcement derived from red banana empty fruit bunches is employed to solve issues related to landfill gas emissions and the simultaneous utilisation of organic wastes. The impact of saline treatment on the physicochemical, thermal, and morphological of CNFs is examined. Compression moulding was utilised to make five different loading levels of SCNFs reinforced epoxy nano composites. The resultant nano composites were evaluated by using mechanical and thermal analysis. The incorporation of SCNFs with a large surface area in epoxy allowed for mechanical interlocking and improved mechanical and thermal characteristics. The composite with the highest strengths and thermal stability was discovered to include 3% wt.% SNCFs. This research shows that combining epoxy with SCNFs has the potential to reduce agro waste while also developing sustainable nano composites with qualities that might be valuable for light-weight structural applications.

Numerical Modeling of Bond Formation in Polymer Surface Metallization Using Cold Spray

Surface metallization of polymeric materials using cold spray technology has gained increasing attention in the past decade. Experimental studies have evidenced multiple challenges of this process regarding continuity and homogeneity of the metallic deposits on polymer substrates. Modeling and simulation tools could be very helpful to assess the efficiency of different strategies suggested for improved deposition at a considerably reduced cost; nevertheless, the efforts to use numerical modeling in this sector have been less successful. Here, we develop a detailed finite element model for the cold spray deposition of metal particles on polymeric substrates to shed light on the underlying deposition mechanisms. The simulation results are compared with the literature experiments to establish the effectiveness of the proposed model. The developed model is able to capture the key phenomena involved in the deposition mechanism particularly the particle and substrate mechanical interlocking and substrate local melting. It is shown that a particle velocity threshold value should be exceeded to achieve an effective mechanical interlocking. The substate thermal domain and melting as well as the effects of particle velocity and size on deformation and particle anchorage are discussed.