Diatoms are unicellular, eukaryotic microalgae inhabiting nearly all aquatic habitats. They are famous for their micro- and nanopatterned silica-based cell walls, which are envisioned for various technologic purposes. Within this review article, we summarize recent in vivo modifications of diatom biosilica with respect to the following questions: (i) Which metals are taken up by diatoms and eventually processed into nanoparticles (NPs)? (ii) Are these NPs toxic for the diatoms and––if so––what factors influence toxicity? (iii) What is the mechanism underlying NP synthesis and subsequent metabolism? (iv) How can the obtained materials be useful for materials science?

Ti6Al4V alloy samples with large pores suitable for bone implants are fabricated by pressing and sintering. Ti6Al4V powder is mixed with different volume fractions of salt particles. The sintering behavior up to 1260 °C is studied by dilatometry and pore features are observed by scanning electron microscopy and X-ray microtomography. Sintered materials with a relative density between 0.26 and 0.97 are obtained. 3D image analysis proves that large pores form a connected network when the amount of salt is 20% and above. The Young’s modulus and the yield stress of sintered materials deduced from compression tests span over wide ranges of values, which are consistent with real bone data. A simple analytical model is proposed to estimate the relative density as a function of the fraction of salt. This model combined with classical Gibson and Ashby’s power equations for mechanical properties can predict the fraction of salt required to obtain prescribed properties.

Chemical vapor deposition (CVD) of graphene has attracted high interest in the electronics industry due to its potential scalability for large-scale production. However, producing a homogeneous thin-film graphene with minimal defects remains a challenge. Studies of processing parameters, such as gas precursors, flow rates, pressures, temperatures, and substrate types, focus on improving the chemical aspect of the deposition. Despite the many reports on such parameters, studies on fluid dynamic aspects also need to be considered since they are crucial factors in scaling up the system for homogenous deposition. Once the deposition kinetics is thoroughly understood, the next vital step is fluid dynamics optimization to design a large-scale system that could deliver the gas uniformly and ensure maximum deposition rate with the desired property. In this review, the influence of fluid dynamics in graphene CVD process was highlighted. The basics and importance of CVD fluid dynamics was introduced. It is understood that the fluid dynamics of gases can be controlled in two ways: via reactor modification and gas composition. This paper begins first with discussions on horizontal tubular reactor modifications. This is followed by mechanical properties of the reactant gasses especially in terms of dimensionless Reynolds number which provides information on gas flow regime for graphene CVD process at atmospheric pressure. Data from the previous literature provide the Reynolds number for various gas compositions and its relation to graphene quality. It has been revealed that hydrogen has a major influence on the fluid dynamic conditions within the CVD, hence affecting the quality of the graphene produced. Focusing on atmospheric pressure CVD, suggestions for up-scaling into larger CVD reactors while maintaining similar fluid properties were also provided.

In this paper, we reviewed recent research in the field of capillary suspensions and highlight a variety of applications in the field of smart materials. Capillary suspensions are liquid–liquid–solid ternary systems where only one liquid is present in a few percent and induces a strong, capillary-induced particle network. These suspensions have a large potential for exploitation, particularly in the production of porous materials since the paste itself and the properties of the final material can be adapted. We also discussed the rheological properties of the suspension and network structure to highlight the various ways these systems can be tuned.

Lignin-based phenol formaldehyde resin was synthesized using phenolated calcium lignosulfonate, and porous carbon with good wettability was prepared after carbonization and potassium hydroxide (KOH) activation. The results indicated that when the KOH to the carbonized sample mass ratio was 6:1, the prepared carbon had a rich porous structure and higher surface area, with a specific surface area of 1320.13 m2/g. Furthermore, the porous carbon exhibited a maximum specific capacitance of 204.88 F/g at a current density of 0.5 A/g in the potential range −1.0 to 0 V in a 6 M KOH solution and a low equivalent series resistance of 0.64 Ω. The phenolated calcium lignosulfonate-based phenol formaldehyde resin porous carbon demonstrated a favorable electric double-layer performance.

Admicellar polymerization, a novel technique for surface modification, was used in this work to enhance the compatibility between polymers with obviously different polarities, e.g., natural rubber (NR) and polylactic acid (PLA). The admicellar polymerization of methyl methacrylate over NR substrates (using potassium peroxodisulfate as an initiator) so-called poly(methyl methacrylate)–natural rubber (PMMA-ad-NR) was prepared and mixed with PLA at different contents (5, 10, and 15 wt%) in comparison to the simple PLA/NR blends. The monomer to initiator ratio was varied: 25:1, 50:1, and 100:1 corresponding to the admicelled PMMA molecular weight of 20,000, 30,000, and 40,000 g/mol, respectively. All PLA/PMMA-ad-NR blends showed good compatibility as evident by FE-SEM results revealing smooth boundary of PMMA-ad-NR domains in the PLA matrix. Moreover, the mechanical properties and thermal stability of PLA/PMMA-ad-NR blends were higher than those of PLA/NR blends, especially with increasing PMMA-ad-NR content up to 10 wt%. It was clear that the lowest molecular weight of the admicelled PMMA gave the highest toughness of PLA/PMMA-ad-NR blends.

Special needs patients often require specific dental treatments and modified restorative materials that reduce clinical discomfort. Starting from glass ionomer cements (GICs), some different fillers were added to improve their mechanical and clinical performances. The effect of nanohydroxyapatite, antibiotic, and mucosal defensive agent on the mechanical and thermal properties of GICs was investigated. Compressive tests, calorimetric analysis, and morphological investigation were conducted. The middle percentages of fillers increased the elastic modulus while the highest decreases are recorded for highest percentages. Filler and environment also influence the compressive strengths and toughness. The introduction of fillers led to a reduction of the enthalpy with a maximum decrease with the middle percentage. The morphological characterization showed a good dispersion of the fillers. The filler percentages should be selected with a compromise between the elastic modulus, the compressive strength, and the curing time. Obtaining new materials with good clinical and mechanical properties can represent an innovative aspect of this work with positive implication in clinical practice, mainly in uncollaborative patients in which the use of traditional protocols is problematic.

The rapid increase and dependency on mobile electronic devices and burgeoning importance of sensor network systems and Internet of Things (IoT) to sustain an aging society indicates the strong need to develop battery-less and mobile power sources. Materials for energy harvesting from environmental sources, including mechanical vibrations, magnetic field, heat, and light have become highly relevant for implementation of the IoT vision that requires self-powered wireless sensor networks for sustainable deployment. The articles in this issue cover piezoelectric materials, magnetoelectrics, and thermoelectrics and provide a summary of state-of-the-art energy-harvesting approaches, various material design strategies being targeted by the community, and fundamental challenges in finding an optimum solution and future roadmap. Flexibility of energy harvesters is also emphasized, given the huge potential for wearables. Photovoltaics are briefly covered with respect to wearables and textiles.

Conjugated polymers have emerged as potential candidates for thermal-energy harvesting. Their flexible and lightweight nature, as well as scalable processing, make them geometrically versatile for a large variety of applications, including powering wearable electronics that are not available for traditional inorganic materials. However, the long-range structural disorder greatly hinders their electrical conduction, and this far outweighs the induced low thermal conductivity; therefore, the thermoelectric performance needs to be significantly improved to fulfill the requirements of efficient devices. Composites and hybrid thermoelectric materials have been developed to capitalize on the individual strengths of conducting polymers and other components, including carbon nanotubes, graphene, and inorganic nanomaterials. In this article, we present recent advances in conjugated polymers, the associated hybrid thermoelectric composites, and the latest breakthroughs in the development of inorganic–organic hybrid superlattices.

By inserting a carbon chain, the geometric structure and electronic properties of carbon nanotube (CNT) would undergo a significant change. Numerous studies have conducted to experimentally find the insertion effect of carbon chains on CNTs. This paper in a theoretical way studied the geometry of carbon chains inserted CNTs and analyzed the mechanism for conductivity change after insertion of carbon chains. Results indicate that carbon chains in the innermost channel of the tube are effective methods for transforming the electrical properties of the CNT, leading to the redistribution of electron and thereby causing the conductivity change in obtained configurations.