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A flexible 3D polymer network that behaves as Bragg reflector able to produce structural coloration with 95% reflectance lightly due to the low crystallinity of PLA (a biodegradable and biocompatible polymer).

Recently, polymers have been attracted great attention because of their thermoelectric materials’ excellent mechanical properties, specifically their cost-effectiveness and scalability at the industrial level. In this study, the electropolymerization conditions (applied potential and deposition time) of PEDOT films were investigated to improve their thermoelectric properties. The morphology and Raman spectroscopy of the PEDOT films were analyzed according to their applied potential and deposition time. The best thermoelectric properties were found in films grown at 1.3 V for 10 min, with an electrical conductivity of 158 ± 8 S/cm, a Seebeck coefficient of 33 ± 1 µV/K, and a power factor of 17 ± 2 µW/K·m2. This power factor value is three times higher than the value reported in the literature for electropolymerized PEDOT films in acetonitrile using lithium perchlorate as a counter-ion. The thermal conductivity was found to be (1.3 ± 0.3) × 10−1 W/m·K. The highest figure of merit obtained at room temperature was (3.9 ± 1.0) × 10−2 using lithium perchlorate as a counter-ion. In addition, three-dimensional (3D) PEDOT nanonetworks were electropolymerized inside 3D anodic aluminum oxide (3D AAO), obtaining lower values in their thermoelectric properties., The authors acknowledge financial support from PID2020-118430GB-I00 and CSIC PIF 2D-MESES. Cristina V. Manzano and Aída Serrano acknowledge funding from Atracción de Talento Investigador de la Comunidad de Madrid, contracts no. 2019-T1/IND-13541 and 2017-t2/IND5395, respectively. O.C.C. acknowledges to micro-TENERGY project from the Ramon Areces’ Foundation. We acknowledge the services of the MiNa Laboratory at IMN and funding from CM (project SpaceTec, S2013/ICE2822), MINECO (project CSIC13-4E-1794) and the EU (FEDER, FSE).

Polymers occupy a central role in current society due to their utility and versatile properties. As part of the class of soft materials, polymers have also been employed in research through nanostructuration and functionalization, looking for the development of new metamaterials with wide applicability in science and society. A particular polymer, Polyethylene, has been widely used both in research and commodities, and new ways to nanostructure and improve its functionality should be considered. Here, we report on the nanostructuration of polyethylene for the fabrication of three-dimensional nanonetworks, by resorting to 3 different variants of polyethylene: low density, high density, and ultra-high molecular weight. Through the melt infiltration of these polymers into well-known three-dimensional interconnected anodic aluminum oxide templates (3D-AAO), a study can be performed to understand the effects of the chain length, structure, and chain-branching of the used polymers on the stability and integrity of the resulting polymeric nanonetworks. This was accomplished by performing infiltrations in the presence of excess bulk material and quenching the infiltration process to access transient infiltration stages. The morphology of these networks was analyzed through SEM and STEM-HAADF to understand the differences arising from polymer structure. The observed results are interpreted through the use of the Lucas-Washburn equation for capillary flow and the determination of the critical contact angle for spontaneous capillary infiltration. The resulting metamaterials also exhibit photonic responses, resulting from the replication of the periodic nature of the employed templates.

Bi2Te3 is the most commonly used thermoelectric material in modern solid-state refrigerators and power generators based on this basic principle. Due to predictions of significant improvements in their efficiency by using nanostructured materials, a thorough study on thin films and nanowires deposited by the electrodeposition method are here presented. The study of the deposition applied potential effect on the morphology, stoichiometry and crystallinity of both thin films and nanowires has been conducted. The morphology and stoichiometry was found to highly depend on the deposition potential, where by increasing it one was able to accurately control the Te% content of the deposits. X-ray diffraction measurements have shown the presence of a strong relation between the material's crystallinity and the deposition potential, where samples ranged from monocrystalline, at very low potentials, to almost completely amorphous, at high potentials. Finally, nanowire diameters were seen to diminish with the applied potential, in conjunction with the general array. Keywords: Electrodeposition, Thin films, Nanowires, Energy harvesting, Morphology

The versatility of Anodic Aluminum Oxide has led to the development of a variety of templates with ranging sizes, periodic modulations, and network-like architectures. These templates allow for the nanostructuration and study of new meta-materials, with interesting and important properties enhanced through size-reduction effects. In this work, we further extend the utility of these templates through the use of current anodization in concentrated Sulfuric acid and 25% V/V of ethanol under low current density values, obtaining small pore architectures with sub-10 nm features. In addition, polymer infiltration was performed as a proof of concept application, resulting in 8 nm nanowires. The templates reduced sizes allow for their application in the search for stable, extremely small diameter nanowires, and also for their use as scaffolds or filters., M.M.G. acknowledges the financial support from the projects INFANTE 201550E072 and MAT2017-86450-c4-3-r. The authors acknowledge the service from the X‐SEM Laboratory at IMN, and funding from MINECO under project CSIC13‐4E‐1794 with support from EU (FEDER, FSE).

The preparation of high-quality, economic and scalable thin films are crucial for future applications in efficient thermoelectric devices. Ion Beam sputtering deposition appears as an elegant solution to tackle this challenge and in this context it will be used in this work. Thus herein, we assess the influence of the beam voltage in the thermoelectric properties through a thorough study of the morphological, chemical and transport properties in the produced thin films. It outcome that beam voltage drastically influences the stoichiometry leading to different crystalline structures that directly affect the thermoelectric properties of the Bi-Te deposited thin films.

The synthesis of flexible photonic materials, by sustainable and scalable methods, is proved to be a difficult task for the materials science and industrial communities. Alongside, the modern society has also grown a strong dependence on polymeric materials, demanding superpolymers that combine functionality and cost with superior after‐use properties. The path for accomplishing this aim is made possible by mimicking nature through the merging of self‐ordered nanostructures and a commodity thermoplastic, resorting to basic fabrication infrastructure. This work presents the development of a flexible material that exhibits tunable structural color due to its 3D polyethylene based nanonetwork. These nanonetworks are hydrophobic, and change color depending on the refractive index of the material filling their voids. This developed flexible metamaterial is projected to open opportunities for the fabrication of economically affordable (around 0.008 € cm−2) and solvent‐free photonic nanostructures with multipurpose applications such as sensing, energy saving, clothing, and photovoltaics, among others., M.M.‐G. acknowledges the financial support from the project TONALITy ERC POC665634 and INFANTE 201550E072. O.C.‐C. acknowledges fruitful discussion with Prof. G. Armelles. R.S. acknowledges the European Commission through the H2020‐MSCA‐IF project TONSOPS (Grant No. 706094). O.C.‐C. acknowledges financial support from Ramon y Cajal research grant (MINECO). The authors acknowledge the service from the X‐SEM Laboratory at IMN, and funding from MINECO under projectCSIC13‐4E‐1794 with support from EU (FEDER, FSE).