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.

APATITIC NANOPOWDERS AND COATINGS: A COMPREHENSIVE REVIEW

The use of artificial biomaterials has been acclaiming potential therapeutic scope in diverse clinical applications. This review started with the description of the basics of biomaterials, and desirable properties, which are the prerequisites to understand biomaterials. The orthopedic biomaterials, their classification and the importance of calcium phosphate (CaP) materials for hard-tissue applications were utterly discussed. Furthermore, among the various CaP biominerals, the importance of hydroxyapatite (HAP) and its synthesis techniques was comprehensively reviewed. The sol–gel route for the synthesis of HAP nanoparticles and deposition of coatings were systematically studied. Among the metallic substrates, Ti6Al4V alloy remained the focus of this study. Moreover, several film pre-preparation methods were also given due importance. The importance of other surface modification techniques, especially in the context of Ti6Al4V substrates, was also discussed. Among several coating techniques to deposit CaP coatings, special attention was paid to the spin and dip coating techniques. In addition to monolithic HAP coatings, reinforced and antimicrobial HAP coatings were also reviewed from broad perspectives. Therefore, this review provides an in-depth insight into the preparation and properties of apatitic nanoparticles and their coatings for orthopedic and dental applications.

Enabling Tunable Hydrophilicity of PDMS via Metal-ligand Coordinated Dynamic Networks

Polydimethylsiloxane (PDMS) has been widely used in various fields due to its appealing physical and chemical properties. However, its high hydrophobicity not only yields poor adhesion to substrates but also facilitates undesired adsorption of substances such as proteins, biofoulers, etc., which limits the performance and lifetime of PDMS. Moreover, traditional surface modification techniques are often not efficient on PDMS surfaces because of the surface reconstruction. Although new methods involving chemical modification have been developed, most of them require complicated procedures and equipment. To overcome this challenge, we incorporate metal-ligand coordination, a non-covalent interaction bearing polar functionality, into PDMS, which exposes the hydrophilicity progressively upon dynamic bond breakage and reformation. We demonstrate that the hydrophilicity of coordinated PDMS can be tailored by the choice of network structure, counter anions, and metal cations, which yield distinct network dynamics. The wetting mechanism is discussed in the context of chain reconfiguration and surface reconstruction. We also show that a properly designed metal-ligand coordinated PDMS has potential as a superior marine fouling release coating by weakening diatom attachment. Through this paper, we introduce a new concept for tuning material hydrophilicity via dynamic polar functionalities, which is applicable to a wide range of polymers.

Multiscale Micro/Nanostructured Heat Spreaders for Thermal Management of Power Electronics

In this chapter, we describe surface modification techniques for enhancing heat/mass transfer and evaporation on heated surfaces. The effect of asymmetrical structure in designing a vapor chamber, patterned with multiscale micro/nanostructured surfaces will be introduced. The wettability patterned surface and its mechanism for improving the evaporation rate of a droplet and the thermal performance of nucleate boiling are discussed. An ultrathin vapor chamber based on a wettability patterned evaporator is introduced as a case for the application of the wettability pattern. Besides, modifying the surface with nanostructure to form a multiscale micro/nanostructured surface or superhydrophobic surface also enhances the phase change. Several types of heat spreaders are proposed to investigate the effects of multiscale micro/nanostructured surface and nanostructured superhydrophobic condenser on the thermal performance of the heat spreaders, respectively. The effects of multiscale micro/nanostructured evaporator surfaces with wettability patterns will be analyzed and experimental data will be presented.

Bimetallic Nanowires on Laser-Patterned PEN as Promising Biomaterials

As inflammation frequently occurs after the implantation of a medical device, biocompatible, antibacterial materials must be used. Polymer–metal nanocomposites are promising materials. Here we prepared enhanced polyethylene naphthalate (PEN) using surface modification techniques and investigated its suitability for biomedical applications. The PEN was modified by a KrF laser forming periodic ripple patterns with specific surface characteristics. Next, Au/Ag nanowires were deposited onto the patterned PEN using vacuum evaporation. Atomic force microscopy confirmed that the surface morphology of the modified PEN changed accordingly with the incidence angle of the laser beam. Energy-dispersive X-ray spectroscopy showed that the distribution of the selected metals was dependent on the evaporation technique. Our bimetallic nanowires appear to be promising antibacterial agents due to the presence of antibacterial noble metals. The antibacterial effect of the prepared Au/Ag nanowires against E. coli and S. epidermidis was demonstrated using 24 h incubation with a drop plate test. Moreover, a WST-1 cytotoxicity test that was performed to determine the toxicity of the nanowires showed that the materials could be considered non-toxic. Collectively, these results suggest that prepared Au/Ag nanostructures are effective, biocompatible surface coatings for use in medical devices.

Preventing Biofilm Formation and Development on Ear, Nose and Throat Medical Devices

Otorhinolaryngology is a vast domain that requires the aid of many resources for optimal performance. The medical devices utilized in this branch share common problems, such as the formation of biofilms. These structured communities of microbes encased in a 3D matrix can develop antimicrobial resistance (AMR), thus making it a problem with challenging solutions. Therefore, it is of concern the introduction in the medical practice involving biomaterials for ear, nose and throat (ENT) devices, such as implants for the trachea (stents), ear (cochlear implants), and voice recovery (voice prosthetics). The surface of these materials must be biocompatible and limit the development of biofilm while still promoting regeneration. In this respect, several surface modification techniques and functionalization procedures can be utilized to facilitate the success of the implants and ensure a long time of use. On this note, this review provides information on the intricate underlying mechanisms of biofilm formation, the large specter of implants and prosthetics that are susceptible to microbial colonization and subsequently related infections. Specifically, the discussion is particularized on biofilm development on ENT devices, ways to reduce it, and recent approaches that have emerged in this field.

Zirconia Materials for Dental Implants: A Literature Review

Titanium is currently the most commonly used material for manufacturing dental implants. However, its potential toxic effects and the gray color have resulted in increasing requests for metal-free treatment options. Zirconia is a type of ceramic materials that has been extensively used in medicine field, such as implant abutments and various joint replacement appliances. Amounts of clinical evaluations have indicated good biocompatibility for zirconia products. Besides, its toothlike color, low affinity for plaque and outstanding mechanical and chemical properties have made it an ideal candidate for dental implants. The aim of this study is to review the laboratory and clinical papers about several kinds of zirconia materials and zirconia surface modification techniques. Although there are plenty of literatures on these topics, most of the researches focused on the mechanical properties of the materials or based on cell and animal experiments. Randomized clinical trials on zirconia materials are still urgently needed to validate their application as dental implants.