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Objectives: A tricalcium silicate-based cement, Biodentine™, has displayed antibiofilm activity when mixed with chitosan powder. This study aimed to assess the effect of chitosan incorporation on the physico-mechanical and biological properties of Biodentine™. Methods: In this study, medium molecular weight chitosan powder was incorporated into Biodentine™ in varying proportions (2.5 wt%, 5 wt%, 10 wt%, and 20 wt%). The setting time was determined using a Vicat apparatus, solubility was assessed by calculating weight variation after water immersion, radiopacity was evaluated and expressed in millimeters of aluminum, the compressive strength was evaluated using an Instron testing machine, and the microhardness was measured with a Vickers microhardness tester. In addition, surface topography of specimens was analyzed using scanning electron microscopy, and the effect of chitosan on the viability of human embryonic kidney (HEK 293) cells was measured by a colorimetric MTT assay. Results: Incorporation of 2.5 wt% and 5 wt% chitosan powder delivered an advantage by speeding up the setting time of Biodentine material. However, the incorporation of chitosan compromised all other material properties and the crystalline structure in a dose-dependent manner. The chitosan-modified material also showed significant decreases in the proliferation of the HEK 293 cells, signifying decreased biocompatibility. Significance: Chitosan incorporation into calcium silicate materials adversely affects the physical and biological properties of the material. Despite the increased antimicrobial activity of the modified material, the diminution in these properties is likely to reduce its clinical value.

Abstract In light of the uprising global development on sustainability, an innovative and environmental friendly wood‐based material derived from natural pinewood has been developed as a high‐performance alternative to petrochemical‐based materials. The wood‐based functional material, named as BC‐CaCl2, is synthesized through the coordination of carboxyl groups (−COOH) present in pinewood with calcium ions (Ca2+), which facilitates the formation of a high‐density cross‐linking structure through the combined action of intermolecular hydrogen bonds. The as‐prepared BC‐CaCl2 exhibits excellent tensile strength (470.5 MPa) and flexural strength (539.5 MPa), establishing a robust structural basis for the materials. Meanwhile, BC‐CaCl2 shows good water resistance, thermal conductivity, thermal stability, UV resistance, corrosion resistance, and antibacterial properties. BC‐CaCl2 represents a viable alternative to petrochemical‐based materials. Its potential application areas include waterproof enclosure structure of buildings, indoor underfloor heating, outdoor UV resistant protective cover, and anti‐corrosion materials for installation engineering, and so forth.

Deep eutectic solvents (DESs) are an emerging class of ionic liquids that offer a solution to reclaiming technology critical metals (TCMs) from electronic waste, with potential for improved life cycle analysis. The high viscosities typical of DESs, however, impose mass transport limitations such that passive TCM removal generally requires immersion over extended durations, in some cases in the order of hours. It is postulated that, through the targeted application of power ultrasound, delamination of key structures in electronic components immersed in DESs can be significantly accelerated, thereby enabling rapid recovery of TCMs. In this paper, we fully characterise cavitation in a Choline Chloride-Ethylene Glycol DES as a function of sonotrode input power, by the acoustic detection of the bubble collapse shockwave content generated during sonications at more than 20 input powers over the available range. This justifies the selection of two powers for a detailed study of ultrasonically enhanced TCM-delamination from printed circuit boards (PCBs). Dual-perspective high-speed imaging is employed, which facilitates simultaneous observation of TCM removal, and the cavitation evolution and interaction with the PCB surface. Bubble jetting is identified as a key contributor to initial pitting of the TCM layers, exposing the larger underlying copper layer, with the contributions of additional inertial cavitation-mediated phenomena such as bubble-collapse shockwaves also demonstrated as important for delamination. Optimal cavitation activity throughout the sonication then promotes etching of the copper base layer of the PCB structure targeted by the DES, liberating the overlaying TCMs in sections as large as 0.79 mm2. We report a thirtyfold improvement in processing time compared to passive delamination, with sonications at the lower power outperforming those at the higher power. The results demonstrate the potential for industrially scalable recovery of TCMs from the growing quantities of global e-waste, using combined power ultrasonics and DESs.

ABSTRACT: Almost ten years after the publication of the first triboelectric nanogenerator (TENG) paper in 2012, this review gives a brief overview of recent technological advances in applying TENG technology to key sustainable and renewable energy applications. The paper examines progress of TENG applications in four key areas such as wearables, wave, wind and transport. TENGs have advanced hugely since its inception and approaches to apply them to a host of freely available sources of kinetic energy have been developed. However, electrical output remains low (mostly less than 500 W/m2) compared to some other forms of energy generation and the main challenges for the future appear to be further boosting output power and current, fabricating advanced TENGs economically and designing TENGs for lifetime survival in various practical environments. It concludes with a discussion of pressing challenges for realizing the full potential of TENGs in these application areas particularly from the perspective of materials and fabrication. It is noted that considerable research and development should be required to enable large-scale manufacture of TENG based devices. TENGs will be instrumental in the future evolution of the Internet of Things (IoTs), human-machine interfacing, machine learning applications and ‘net-zero emission’ technologies.

The relationship between material failure and surface roughness has been investigated using two titanium alloys: Ti64 and the more ductile Ti407. Three surface types were created (polished, sandblasted and scratched) with instances spanning a wide range of average roughness. The surfaces were tested in three-point bending with the imparted roughness on the tensile under-surface of a rectangular beam specimen. Results showed failure of Ti64 to be highly sensitive to both magnitude and orientation of roughness. High roughness in the maximum tensile stress direction (and scratch like features perpendicular to this direction) were most detrimental. Thus, strain-to-failure (and work-to-failure) in Ti64 dropped off significantly with increasing surface roughness in the tensile direction. Finite element modelling of the test indicated that cracks initiate at zones of high plastic strain at the tips of roughness valleys due to high local surface curvature. Thus, roughness can be considered as a series of blunt crack-like features where larger crack tip curvature induces greater likelihood of crack propagation. Contrastingly, the mechanical response of Ti407 was insensitive to surface roughness owing to its significantly greater ductility. Thus, designers need to be aware of the sensitivity of failure of particular materials to surface roughness. The insensitivity of Ti407 is advantageous, but the sensitivity of failure to surface roughness in a material like Ti64 is potentially serious if not properly accounted for.

In this current energy crisis era, piezoelectric and triboelectric effects are emerging as promising technologies for energy harvesting. Polyvinylidene fluoride (PVDF) and its copolymers are well-known piezoelectric materials with high piezoelectric coefficients, which are widely used in flexible electronic devices. PVDF is also greatly utilized in the preparation of triboelectric layer due to its higher electronegative nature amongst common polymers. On the other hand, zinc oxide (ZnO) has been widely studied to investigate its multifunctional properties, including piezoelectricity, pyroelectricity and antibacterial activity. This versatile material can be prepared, using low cost and environmentally friendly routes, in various morphologies. Various research has already been performed to capture the synergistic effects of reinforcing ZnO within the PVDF polymeric matrix. This work first describes the basic principles of piezoelectric and triboelectric effects. Thereafter, the piezoelectric and triboelectric performances of PVDF and ZnO-based materials are briefly depicted based on their structures. Finally, the challenges and future scope associated with the mechanical energy harvesting from such materials are highlighted.