A Simple Two-Dimensional Model System to Study Electrostatic-Self-Assembly

This paper surveys the variables controlling the lattice structure and charge in macroscopic Coulombic crystals made from electrically charged, millimeter-sized polymer objects (spheres, cubes, and cylinders). Mechanical agitation of these objects inside planar, bounded containers caused them to charge electrically through contact electrification, and to self-assemble. The processes of electrification and self-assembly, and the characteristics of the assemblies, depended on the type of motion used for agitation, on the type of materials used for the objects and the dish, on the size and shape of the objects and the dish, and on the number of objects. Each of the three different materials in the system (of the dish and of the two types of spheres) influenced the electrification. Three classes of structures formed by self-assembly, depending on the experimental conditions: two-dimensional lattices, one-dimensional chains, and zero-dimensional ‘rosettes’. The lattices were characterized by their structure (disordered, square, rhombic, or hexagonal) and by the electrical charges of individual objects; the whole lattices were approximately electrically neutral. The lattices observed in this study were qualitatively different from ionic crystals; the charge of objects had practically continuous values which changed during agitation and self-assembly, and depended on experimental conditions which included the lattice structure itself. The relationship between charge and structure led to the coexistence of regions with different lattice structures within the same assembly, and to transformations between different lattice structures during agitation.Chemistry and Chemical Biolog

Super elastic and negative triboelectric polymer matrix for high performance mechanoluminescent platforms

Mechanoluminescence platforms, combining phosphors with elastic polymer matrix, have emerged in smart wearable technology due to their superior elasticity and mechanically driven luminescent properties. However, their luminescence performance often deteriorates under extreme elastic conditions owing to a misinterpretation of polymer matrix behaviour. Here, we unveil the role of the polymer matrices in mechanoluminescence through an interface-triboelectric effect driven by elasticity, achieving both high elasticity and brightness. By investigating interactions between elastic polymers and copper doped zinc sulphide microparticles, we reveal that elasticity significantly governed triboelectric effects for mechanoluminescence. In particular, high negative triboelectricity emerged as the key to overcoming poor triboelectric effect in extreme elastic conditions. This led to the discovery of polybutylene adipate-co-terephthalate silane and polycarbonate silane, achieving remarkable elasticity over 100% and a brightness of 139 cd/m2. These findings offer fundamental insights to select the optimal polymer matrix based on systematic parameters for various smart wearable applications

Polarity switch of PMMA powder transported through a PMMA duct

During pneumatic conveying, powder electrifies rapidly due to the high flow velocities. In our experiments, the particles even charge if the conveying duct is made of the same material, which might be caused by triboelectrification between two asymmetric contact surfaces. Surprisingly, we found the airflow rate to determine the polarity of the overall powder charge. This study investigates the charging of microscale PMMA particles in turbulent flows passing through a square PMMA duct. The particles are spherical and monodisperse. A Faraday at the duct outlet measured the total charge of the particles. At low flow velocities, the particles charged negatively after passing through the duct. However, the powder's overall charge switched to a positive polarity when increasing the flow velocity

Perspectives on the Lindman Hypothesis and cellulose interactions

In the history of cellulose chemistry, hydrogen bonding has been the predominant explanation when discussing intermolecular interactions between cellulose polymers. This is the general consensus in scholarly textbooks and in many research articles, and it applies to several other biomacromolecules’ interactions as well. This rather unbalanced description of cellulose has likely impacted the development of materials based on the processing of cellulose—for example, via dissolution in various solvent systems and regeneration into solid materials, such as films and fibers, and even traditional wood fiber handling and papermaking. In this review, we take as a starting point the questioning of the general description of the nature of cellulose and cellulose interactions initiated by Professor Björn Lindman, based on generic physicochemical reasoning about surfactants and polymers. This dispute, which became known as “the Lindman hypothesis”, highlights the importance of hydrophobic interactions in cellulose systems and that cellulose is an amphiphilic polymer. This paper elaborates on Björn Lindman’s contribution to the subject, which has caused the scientific community to revisit cellulose and reconsider certain phenomena from other perspectives.info:eu-repo/semantics/publishedVersio

Opportunities and challenges in triboelectric nanogenerator (TENG) based sustainable energy generation technologies: a mini-review

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

A critical review on polyvinylidene fluoride (PVDF)/zinc oxide (ZnO) based piezoelectric and triboelectric nanogenerators

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

Polymer Materials in Sensors, Actuators and Energy Conversion

Polymer-based materials applications in sensors, actuators, and energy conversion play a key role in recently developing areas of smart materials and electronic devices. These areas cover the synthesis, structures, and properties of polymers and composites, including energy-harvesting devices and energy-storage devices for electromechanical (electrical to mechanical energy conversion) and magneto-mechanical (magnetic to mechanical energy conversion), light-emitting devices, and electrically driving sensors. Therefore, the modulation of polymer-based materials and devices for controlling the detection, actuation, and energy with functionalized relative device can be achieved with the present reprint, comprising 12 chapters.This reprint is principally concerned with the topic of materials of materials, especially polymers. The contents not only involve essential information but also possess many novel academic applications in the fields. This Special Issue's title is "Polymer Materials in Sensors, Actuators and Energy Conversion" and covers the research field of polymers .Finally, I am very proud of my dear wife Winnie, son Vincent, and daughter Ruby. I thank them for supporting me in finishing the reprint. The reprint, involving 2 reviews and 10 regular papers, has been accomplished, and I am deeply thankful to all the authors for their assistance in producing a reprint with considerable number of chapters. I also hope that readers can achieve some useful understanding of polymer materials in sensors, actuators, and energy conversion, and that that they will be employed by scientists and researchers

Engineering Surface Wettability for Passive Liquid Transportation and Energy Harvesting

Manipulating droplet motion is essential across a wide range of scientific and engineering fields, as many processes depend on the precise handling, transport, and interaction of droplets at solid-liquid interfaces. Nature has evolved surfaces that efficiently regulate liquid movement, inspiring the development of artificial surfaces with asymmetric wettability gradients. These engineered surfaces offer significant potential in applications such as microfluidics, heat transfer, functional textiles, and oil-water separation, providing advanced solutions for fluid management.This thesis focuses on understanding liquid dynamics at interfaces and designing wettability-patterned surfaces capable of directional droplet transport over a wide range of surface tension. Effective droplet motion requires overcoming surface resistance, minimized here using liquid-like polymer brushes. We demonstrate that surfaces patterned with two distinct polymer brush chemistries can transport both water and low surface tension (LST) liquids that typically spread on natural surfaces. Reduced contact line pinning enables lossless, long-range transport, achieving distances an order of magnitude greater than previously reported. We also show that more complex designs can perform microfluidic tasks such as droplet splitting, mixing, and guided transport. These surfaces also enhance dropwise condensation of LST liquids, showing potential in heat transfer systems. Wettability patterning of polymer brush-coated surfaces provides precise control over contact line dynamics, further enabling a detailed exploration of the relationship between droplet contact line motion and triboelectrification. We investigate triboelectrification at the interface of liquids and polymer brush-coated surfaces through sliding droplet experiments, highlighting the roles of surface chemistry, contact angle hysteresis, and droplet dynamics in influencing triboelectric performance. Additionally, we study the triboelectric behavior of droplets compressed between two polymer brush surfaces to isolate the effect of the change in contact area, and we find it affects current output more than droplet velocity or total contact area. Finally, we extend this work to textiles by applying asymmetric wettability to porous materials for passive liquid transport. We introduce a novel fabric design that combines chemical and physical wettability patterns, enabling efficient sweat and water removal in highly humid environments.Ph.D

Materials from renewable resources: new properties and functions

Sustainable production requires increasing use of raw materials from renewable sources, processed under mild conditions with minimal effluent production. These requirements are satisfied by using materials derived from biomass, in synergy with food and energy production. The possibilities of biomass are continuously enlarged by new findings, as in the intrinsic nanocomposite properties of natural rubber and the amphiphile behavior of cellulose that translated into new functional materials, including high-performance, flexible and conductive non-metallic materials. Other findings are allowing a better understanding of electrostatic phenomena that play a positive role in electrostatic adhesion and cohesion of nanocomposites made from biomass products. Moreover, this should allow the development of safe electrostatic separation techniques, suitable for the fractionation of crude mixtures of biomass residues. A current study on rubber electrostatics is showing its capabilities as a transducer of mechanical energy while providing clues to understand the performance of the dielectric elastomers used in robotic self-sensing actuators914CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP465452/2014-088887.284776/2018-002014/50906-

Roadmap on energy harvesting materials

Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere