Antifouling performance of copper-containing fused filament fabrication (FFF) 3-D printing polymer filaments for marine applications

Extrusion and 3D printing of novel lipid-polymer blends for oral drug applications

Lipids are interesting biological materials that can offer a number of pharmaceutical benefits when used as carriers for drug delivery. However, 3D printing of lipids alone by fused deposition processing techniques is very difficult as they have very poor mechanical properties that cause their filaments to fail when they are loaded into a fused deposition 3D printer. If this problem could be overcome, then lipids could be 3D printed into bespoke tablets and assist progress towards such personalised medicines. This work aims to improve the mechanical properties of lipid filaments by developing novel lipid-EVA (ethylene vinyl acetate) blends suitable for 3D printing. Different types of lipids in varying proportions were melt blended with EVA and extruded using a micro compounder. The ultimate printability of the materials was tested by feeding the filaments into a material extrusion 3D printer. Flexural testing of the extruded blends demonstrates that a good balance between the strength and flexibility is required for a material to be printable and it was found that a filament has to have a modulus/strength ratio between 8 and 25 in order to be printable. SEM analysis of the fracture surface shows a network structure within the lipid matrix that could be playing a role in the improved properties of the best performing blends. DSC thermograms show a shift in thermal transitions, suggesting some level of miscibility of the components that could have contributed to a more robust structure. The TGA results show an onset of degradation of the blends greater than 200 °C, indicating that the materials can readily withstand the extrusion and printing temperatures. This study demonstrates the successful extrusion and 3D printing of novel EVA-lipid blends with lipid contents of up to 90%.

Materials Selection for Antifouling Systems in Marine Structures

Fouling is the accumulation of unwanted substances, such as proteins, organisms, and inorganic molecules, on marine infrastructure such as pylons, boats, or pipes due to exposure to their environment. As fouling accumulates, it can have many adverse effects, including increasing drag, reducing the maximum speed of a ship and increasing fuel consumption, weakening supports on oil rigs and reducing the functionality of many sensors. In this review, the history and recent progress of techniques and strategies that are employed to inhibit fouling are highlighted, including traditional biocide antifouling systems, biomimicry, micro-texture and natural components systems, superhydrophobic, hydrophilic or amphiphilic systems, hybrid systems and active cleaning systems. This review highlights important considerations, such as accounting for the effects that antifouling strategies have on the sensing mechanism employed by the sensors. Additionally, due to the specialised requirements of many sensors, often a bespoke and tailored solution is preferential to general coatings or paints. A description of how both fouling and antifouling techniques affect maritime sensors, specifically acoustic sensors, is given.

Biomimetic and bioinspired surface topographies as a green strategy for combating biofouling: a review

Biofouling refers to the adverse attachment and colonization of fouling organisms, including macromolecules, bacteria, and sessile invertebrates, on the surfaces of materials submerged in aquatic environments. Almost all structures working in watery surroundings, from marine infrastructures to healthcare facilities, are affected by this sticky problem, resulting in massive direct and indirect economic loss and enormous cost every year in protective maintenance and remedial cleaning. Traditional approaches to preventing marine biofouling primarily rely on the application of biocide-contained paints, which certainly impose adverse effects on the ocean environment and marine ecology. Biomimicry offers an efficient shortcut to developing environmentally friendly antifouling techniques and has yielded encouraging and promising results. The antifouling strategies learned from nature can be broadly classified into two categories according to the nature of the cues applied for biofouling control. One is the chemical antifouling techniques, which are dedicated to extracting the effective antifoulant compounds from marine organisms and synthesizing chemicals mimicking natural antifoulants. In contrast, the physical biomimetic (BM) antifouling practices focus on the emulation and optimization of the physical cues such as micro and nanoscale surface topographies learned from naturally occurring surfaces for better antifouling efficacy. In this review, a synopsis of the techniques for manufacturing the BM and bioinspired (BI) antifouling surface topographies is introduced, followed by the bioassay to assess the antifouling performance of the structured surfaces. Then, the BM and BI surface topographies that were reported to possess enhanced antifouling competence are introduced, followed by a summary of theoretical modeling. The whole paper is concluded by summarizing the studies' deficiencies so far and outlooking the research directions in the future.