Ferroelectricity in Hf0.5Zr0.5O2 (HZO) originates from a polymorphic landscape where the metastable orthorhombic phase competes with monoclinic and tetragonal forms, making functional properties highly sensitive to structural instability. Recent strategies have exploited ionic-vacancy mechanisms, either through redox interactions with the environment or by employing ferroionic heterostructures, to enhance ferroelectric performance. Here, we embrace the ferroionic heterostructure approach and demonstrate that dynamic oxygen-vacancy exchange at epitaxial junctions produces an active interplay between ferroelectric and ionic layers. Epitaxial heterostructures with La0.67Sr0.33MnO3-delta (LSMO), yttria-stabilized ZrO2-delta (YSZ), and Gd-doped CeO2-delta (CGO) reveal coupled electro-chemo-mechanical responses, including ferroelectric diode characteristics and subtle lattice distortions. Epitaxial fluorite-fluorite interfaces act as vacancy-exchange gates that bias polymorphism, enhance polarization, strengthen piezoelectric response, and suppress leakage, in contrast to the electronically dominated perovskite-fluorite junctions. These findings show that ferroionic heterostructures host reciprocal vacancy-driven dynamics, establishing them as a platform for defect-programmable ferroelectricity and tunable functionality in hafnia-based oxides.

The stability of the polarization state in Na0.5Bi0.5TiO3 (NBT) ceramics has been a long-standing problem for its use in piezoelectric applications at elevated temperatures. It has been generally believed that the polarization state, depolarization temperature, and depolarization process are all linked to the grain size in these materials. In this work, we perform a thorough Piezoresponse Force Microscopy (PFM) study of the NBT ceramic samples with substantially different grain sizes sintered as a function of temperature. As-grown, macroscopically poled, and locally poled samples were investigated focusing on the polarization behavior at depolarization temperature. Switching Spectroscopy PFM (SS-PFM) measurements were conducted as a function of grain size and temperature. No direct correlation is observed between the grain size and the switching parameters in any sample. However, temperature-dependent measurements reveal significant differences that are explained by different concentrations of oxygen vacancies. We rationalized the observed behavior, e.g. apparent stabilization of the locally probed polarization above the depolarization temperature, by accumulation and depletion of oxygen vacancies in the vicinity of the internal boundary of the poled region. Significant asymmetry of the PFM hysteresis loops at elevated temperatures confirms this assumption.

The electromechanical properties of hafnium zirconium oxide fluorite (Hf0.5Zr0.5O2, HZO) remain largely unexplored despite its widespread use as a ferroelectric in CMOS-compatible devices. Here, we demonstrate that electrostriction-driven phase instability enables a giant pseudo-piezoelectric response in epitaxial HZO thin films. Above a critical field of 24 kilovolts per centimeter, field-induced transitions between nonpolar and polar phases activate an extrinsic piezoelectric response of ~1000 picometers per volt and bias-stabilized pseudo-piezoelectric strains exceeding 10,000 picometers per volt. This behavior arises from a combination of large electrostriction (M = 1 × 10-14 square meters per square volt), ferroelastic softness, and structural reconfiguration, rather than intrinsic polarization switching. Multimodal characterization combining interferometry, diffraction methods, scanning probe microscopy, and first-principles modeling confirms the coupling between strain and metastable phase dynamics. These findings reveal a previously unrecognized mechanism for functional strain generation in fluorite oxides, positioning HZO as a versatile platform for strain-engineered actuators, adaptive metasurfaces, and reconfigurable nanoelectromechanical systems.

The search for lead-free ferroelectrics, driven by environmental concerns, has continued for decades, yet no material has fully replaced PbZrTiO3-based compositions. Introducing core-shell architectures offers a promising route to enhance functional properties; however, their realization in lead-free systems remains limited. In this work, we present a novel method for obtaining core-shell structures in fully sintered lead-free ferroelectric ceramics by thermally treating two ceramic plates in direct contact-hereafter referred to as the contact method. This approach enabled core-shell formation in BaTiO3, SrTiO3, and Na0.5Bi0.5TiO3 systems through interfacial diffusion. Bi over-stoichiometry in NBT strongly promoted shell formation and enhanced interdiffusion, yielding high chemical contrast with diffusion depths exceeding 300 & micro;m. Furthermore, a fully developed core-shell architecture in BaTiO3 was obtained, resulting in a significant improvement in resistivity. These findings demonstrate the potential of the contact method as a simple and versatile route for tailoring the microstructure and functional properties of lead-free ferroelectric ceramics.

Abstract Surface-initiated polymerizations generate thin films (“brushes”) consisting of polymer chains that are anchored with one chain end to a solid surface. As they are conducted from initiator-modified solid substrates, these polymerizations allow for unidirectional chain growth and enforce a stretched chain conformation. Using acrylonitrile as an example of a monomer with a dipolar side-chain functional group, this study finds that surface-initiated polymerization not only impacts the alignment and conformation of the polymer main chain but can also influence the orientation of side-chain functional groups. Surface-initiated polymerization of acrylonitrile is found to result in polyacrylonitrile (PAN) brushes that display spontaneous pyro- and piezoelectric behavior. As these properties are not observed in spin-cast PAN films, this indicates that surface-initiated growth of PAN enforces an overall parallel orientation of the dipolar nitrile side-chain functional groups. This is supported by polarized FTIR spectroscopy and NEXAFS experiments, which suggest an overall nonisotropic orientation of nitrile groups in the PAN brush, whereas the nitrile groups in the spin-cast PAN film are more isotropically oriented. Pyro- and piezoelectric polymers are attractive for use in sensors, actuators, and energy-harvesting devices but typically require electrical poling, mechanical stretching, or electrospinning to promote the alignment of molecular dipoles and enhance piezo- and pyroelectric properties. The ability to prepare thin polymer films that display spontaneous pyro- and piezoelectric behavior is significant as it renders these postprocessing steps unnecessary.

This allows prediction of the time evolution of the multiple DOFs, as well as electrical outputs from predetermined initial conditions and input forces/torques or prescribed trajectories. Power densities up to 5.44 mW/ cm3 (5.44 kW/m3) and efficiencies up to 48.5% were experimentally found in the literature. Nevertheless, no relationship has been widely explored yet between the increasing power density and the increasing sensitivity of the generators to mechanical excitations with a wide range of DOFs. Even though significant advances have already achieved in this field, our findings highlight that future research must focus on developing sophisticated generators with the ability to effectively couple all translational and rotational DOFs from both kinetic and potential energy, ensuring the minimization of coil Ohmic losses and maximization of the electromechanical coupling coefficient, and thus energy conversion efficiency, for multi-DOF excitations and loads.

The paper presents modeling and quantum-chemical calculations of polar and photoelectronic properties of helix-like peptide nanotubes (PNTs) based on dileucine (LL) and diisoleucine (II) with nanochannels filled with water molecules. Physical properties of LL-based PNTs are close to those of diphenylalnine (FF) PNTs, whereas II-based PNTs demonstrate lower polarization but higher band gap corresponding to the absorption in the UV-C region. Moreover, polarization of LL and II PNTs depends on the chirality of the individual dipeptides and is significantly higher for l-LL and l-II, similar to what is observed for FF PNTs. Water molecules in the internal cavity of PNTs weakly affect their polar properties, whereas noticeably change the HOMO and LUMO energy levels and reduce the bang gap.

Electroactive biomaterials and, in particular, piezoelectric ones are gaining insight into tissue engineering and biomedical applications. Collagen is one of the most available biomaterials found in nature, and the present study focus on the evaluation of its piezoelectric response. Collagen extracted from bovine skin was used and the piezoelectric response was correlated to the physicochemical, thermal, morphological and mechanical properties. A dense fibrillar microstructure was observed and the mechanical properties, which depend on the specific amino acids composition, showed tensile strength and maximum strain values of 34 MPa and 18 %, respectively. Collagen films exhibited approximately 25 % weight loss after 1 day in PBS solution, increasing to about 30 % and 100 % at day 2 and 4, respectively. A piezoelectric response of 0.44 pm/V was obtained, demonstrating the collagen film suitability for electroactive materials in biomedical applications.

Polydopamine (PDA) has emerged as a widely used coating for various materials due to its unique properties such as robustness, biocompatibility, and antioxidant and photothermal activities. PDA coatings are usually prepared through autoxidation of dopamine under alkaline conditions, but this approach is generally timeconsuming and requires high concentrations of the starting monomer. To overcome these drawbacks, enzymatic catalysis has emerged as a novel approach, allowing also to work in a wider range of pH values. In this work, the laccase-assisted dopamine polymerization and PDA film formation have been systematically investigated and optimized by varying reaction parameters, including dopamine and laccase concentrations as well as stirring speed and deposition time. The best results have been obtained at a low dopamine concentration (2.5 mM) in the presence of 0.25 mg/mL of laccase at pH 5.5, and under high stirring (1250 rpm). Under these conditions, laccase-assisted PDA film deposition resulted in significantly improved coating formation than that obtained through traditional autoxidation at pH 8.5 or sodium periodate-induced oxidation at pH 5.5 by approximately 5-and 1.6-fold, respectively. Insights into the chemical structure and morphological features of the PDA coatings were obtained by liquid chromatography-ultraviolet detection-mass spectrometry (LC-UV-MS), atomic force microscopy (AFM), kelvin-probe force microscopy (KPFM) and attenuated total reflectance-Fourier-transform infrared (ATR-FTIR) spectroscopy analysis. In addition, water contact angle (WCA) measurements were performed. These results provide a significant step forward for the obtainment of organic coatings under mild and sustainable conditions opening new possibilities for future applications in PDA-based functional materials.

By introducing a symmetry-reduction design strategy in adamantane derivatives, overcoming the inherent high symmetry of globular molecules that typically hinders long-range electrical ordering, we report a metal-free ferroelectric 2-adamantylammonium bromide (2-ADAB) with a high Curie temperature of 383 K and robust polarization switching.

The temperature-frequency dependence of dielectric permittivity in Na0.5Bi0.5TiO3 (NBT) -based compositions displays a diffused, frequency-independent maximum along with a frequency-dependent shoulder below this maximum. This behavior deviates from that of both classical ferroelectrics and conventional relaxor ferroelectrics, and its interpretation is further complicated by challenges in linking it to known structural phase transitions. This study proposes a new interpretation of the dielectric behavior of NBT-based materials through a comparative analysis of temperature-frequency permittivity data in both unpoled and poled NBT samples and 0.95Na0.5Bi0.5TiO3-0.05CaTiO3 solid solution over a broad frequency range (10 Hz-100 MHz). Results reveal that the steep permittivity change between the maximum and shoulder-accompanied by pronounced thermal hysteresis-can be attributed to a phase transition between two non-ferroelectric phases. When this contribution is excluded, the dielectric response aligns with classical relaxor ferroelectric behavior. To reconcile this with other known properties of NBT, the "breathing" model is employed, offering a unified framework for understanding its relaxor-like characteristics.

Spider silk demonstrates an impressive balance of high strength and elasticity, which results from the hierarchical self-assembled structure of spider silk proteins during the fiber biosynthesis and spinning process. Enhancing the mechanical characteristics of spider silk fibers and imparting them with functional properties has garnered considerable attention. This challenge underscores the importance of developing strategies for modifying native spider silk. In this study, we introduce an approach to modify the structure and properties of spider silk fibers by injecting magnetite hydrosols directly into the spiders' silk glands. This results not only in the magnetic functionality of spider silk fibers but also in 82% increase in Young's compared to native spider silk, along with hardness of 1.30 MPa. To explore the nature of this phenomenon, we analyzed the difference in the topography of native Holothele incei spider silk and Fe3O4-hybrid spider silk, as well as their corresponding mechanical behavior at the nanoscale. Additionally, we studied the changes in structure, composition, and morphology caused by the inclusion of magnetic nanoparticles. Our findings demonstrate that the polar and hydrophobic interactions between Fe3O4 nanoparticles and the amino acid residues in spider silk could influence Young's modulus and hardness of the Fe3O4/spider silk hybrid fibers by promoting the protein conformation from an amorphous phase to β-sheets. This can only be achieved when nanomaterials are integrated into the structure within the fiber. The developed approach enables the fabrication of modified spider silk fibers, which can aid in the fundamental study of native spider silk and the development of technologies to fully replicate the properties of native silk in the future. Furthermore, lightweight, flexible, but strong materials are critical in soft robotic applications, where these nanohybrid fibers not only ensure gentle manipulation and reliability, but also their magnetic properties allow for responsive movement and control.

The development of photoresponsive ferroelastics, which couple light-induced macroscopic mechanical and microscopic domain properties, represents a frontier in materials science with profound implications for advanced functional applications. In this study, we report the rational design and synthesis of two new organic-inorganic hybrid ferroelastic crystals, (MA)(Me4N)[Fe(CN)5(NO)] (MA = methylammonium) (1) and (MA)(Me3NOH)[Fe(CN)5(NO)] (2), using a dual-organic molecular design strategy that exploits hydrogen-bonding interactions for tailoring ferroelastic properties. Specifically, 1 exhibits a two-step phase transition at 138 and 242 K, while the introduction of a hydroxyl group in 2 stabilizes its ferroelastic phase to a significantly higher temperature, achieving a phase transition at 328 K, 86 K above that of 1. This enhancement is attributed to hydrogen bonding between the hydroxyl group of Me3NOH+ and the nitroprusside anion, which suppresses lattice dynamics and reinforces structural stability. Remarkably, 2 demonstrates a large spontaneous strain of 0.153, vastly exceeding the 0.021 of 1, and undergoes an 11% size change along the b-axis in response to thermal stimuli. Both compounds exhibit reversible, photoinduced nitrosyl-linkage isomerization, as confirmed by IR spectroscopy, transitioning between the ground state (N-bound nitrosyl) and the metastable state (O-bound nitrosyl). This integration of photoresponsive functionality with ferroelastic properties establishes a versatile platform for energy-efficient actuation, adaptive devices, and multifunctional sensing applications. These findings offer an innovative pathway for designing next-generation hybrid materials with enhanced tunable properties.

The rising interest in biodegradable polymers like PLLA is gaining attention for their potential in next-generation biomedical devices. One of the critical challenges in leveraging PLLA's full potential is enhancing its crystallinity, as it greatly influences mechanical, thermal, degradation, and piezoelectric properties, which are essential for various applications. Here, we use thermal annealing and strain engineering to transform the amorphous phase into a more ordered crystalline structure. Through various characterization techniques, we show that crystallinity increased progressively from 34.8% in unprocessed films to 57.4% at 100% strain. Terahertz time-domain spectroscopy is employed to gain insights into the structural and dynamic properties where we study low-frequency molecular vibrations and anisotropic properties, enabling simultaneous evaluation of structural, such as crystallinity, and optical characteristics. Rotational analysis provides direct evidence of molecular orientation and birefringence induced by mechanical processing. These findings align strongly with the traditional characterization techniques (XRD, WAXS, DSC, and FTIR). Piezoresponse force microscopy shows that the VPFM signal increased from 0.65 ± 0.15 pm V-1 in unprocessed films to 6.5 ± 1.5 pm V-1 at 100% strain. The in-depth work is an important step in gaining a deeper understanding of how the crystalline regions form, evolve under different processing conditions, and influence PLLA's overall properties.

Nanoscale flows of liquids can be revealed in various biological processes and underlie a wide range of nanofluidic applications. Though the integral characteristics of these systems, such as permeability and effective diffusion coefficient, can be measured in experiments, the behaviour of the flows within nanochannels is still a matter of speculation. Herein, we used a combination of quadrupolar solid-state NMR spectroscopy, computer simulation, and dynamic vapour sorption measurements to analyse water diffusion inside peptide nanochannels. We detected a helical water flow coexisting with a conventional axial flow that are independent of each other, immiscible, and associated with diffusion coefficients that may differ up to 3 orders of magnitude. The trajectory of the helical flow is dictated by the screw-like distribution of ionic groups within the channel walls, while its flux is governed by external water vapour pressure. Similar flows may occur in other types of nanochannels containing helicoidally distributed ionic groups and be exploited in various nanofluidic lab-on-a-chip devices.

This work presents for the first time one-step ultrafast (precursor-free) synthesis of 1D MnFe 2 O 4 (MFO) nanorods and soft magnetic colloidal nanoparticles (NPs) using microwave-assisted hydrothermal (MAH) methods, with or without citric acid (CA) as a surfactant ( in situ synthesis), respectively. The mechanism of growth of spinel MFO nanostructures during the MAH synthesis was studied by varying synthesis duration (3 - 6 h) and temperature (180 - 200 degrees C). An increase in both the duration and temperature improved the purity of the samples, up to 97%. On the other hand, a temperature increase by 20 degrees C notably shortened the formation time of MFO nanorods, which have an average diameter and length of less than 20 nm and 350 nm, respectively, as observed at 200 degrees C after 6 h. All the fabricated MFO NPs with spherical and rod-like morphologies manifested high saturation magnetization in the range of 54 - 64 emu/g. The chelation of lattice metal ions by CA resulted in the formation of a stable colloid comprising 100% pure spinel MFO NPs with a size of <= 32 +/- 10 nm (mean +/- SD) and featuring very soft magnetic properties. This colloid was generated by the MAH synthesis at 175 degrees C within 30 min. Notably, an increase in synthesis duration from 30 min to 3 h diminished MFO phase purity from 100% to 52% and saturation magnetization from 43.4 +/- 0.7 to 33.9 +/- 2.0 emu/g for CA-functionalized MFO NPs owing to CA degradation increasing during the in situ MAH synthesis with longer duration. This study indicates good potential of ultrafast MAH synthesis for the development of 1D magnetic spinel nanostructures with controllable morphology, size, magnetic properties, and colloidal stability, thereby offering a wide range of applications within the fields of adsorption, catalysis, electronics, and biomedicine.

Material thermal conductivity is a key factor in various applications, from thermal management to energy harvesting. With microstructure engineering being a widely used method for customizing material properties, including thermal properties, understanding and controlling the role of extended phonon-scattering defects, like grain boundaries, is crucial for efficient material design. However, systematic studies are still lacking primarily due to limited tools. In this study, we demonstrate an approach for measuring grain boundary thermal resistance by probing the propagation of thermal waves across grain boundaries with a temperature-sensitive scanning probe. The method, implemented with a spatial resolution of about 100 nm on finely grained Nb-substituted SrTiO3 ceramics, achieves a detectability of about 2 x 10(-8 )K m(2) W-1, suitable for chalcogenide-based thermoelectrics. The measurements indicated that the thermal resistance of the majority of grain boundaries in the STiO3 ceramics is below this value. While there are challenges in improving sensitivity, considering spatial resolution and the amount of material involved in the detection, the sensitivity of the scanning probe method is comparable to that of optical thermoreflectance techniques, and the method opens up an avenue to characterize thermal resistance at the level of single grain boundaries and domain walls in a spectrum of microstructured materials.

Using Landau-Ginzburg-Devonshire (LGD) phenomenological approach we analyze the bending-induced re-distribution of electric polarization and field, elastic stresses and strains inside ultrathin layers of van der Waals ferrielectrics. We consider a CuInP2S6 (CIPS) thin layer with fixed edges and suspended central part, the bending of which is induced by external forces. The unique aspect of CIPS is the existence of two ferrielectric states, FI1 and FI2, corresponding to big and small polarization values, which arise due to the specific four-well potential of the eighth-order LGD functional. When the CIPS layer is flat, the single-domain FI1 state is stable in the central part of the layer, and the FI2 states are stable near the fixed edges. With an increase of the layer bending below the critical value, the sizes of the FI2 states near the fixed edges decreases, and the size of the FI1 region increases. When the bending exceeds the critical value, the edge FI2 states disappear being substituted by the FI1 state, but they appear abruptly near the inflection regions and expand as the bending increases. The bending-induced isostructural FI1-FI2 transition is specific for the bended van der Waals ferrielectrics described by the eighth (or higher) order LGD functional with consideration of linear and nonlinear electrostriction couplings. The isostructural transition, which is revealed in the vicinity of room temperature, can significantly reduce the coercive voltage of ferroelectric polarization reversal in CIPS nanoflakes, allowing for the curvature-engineering control of various flexible nanodevices.

The study of cellular ion channels forms a basic understanding of healthy organ functioning and the body as a whole; however, the native role of signal transmission through ion channels between cells remains unclear. The success of the signal transmission investigation depends on the methods and materials used. Therefore, it is necessary to develop a new approach and system for studying detecting cell–cell communication. In this work, we suggest the system of hydroxyapatite patterns demonstrating piezoresponse in conjunction with fiber-based biosensors for detection of electrical signaling in cellular communities. Our system does not disrupt the integrity of cell membrane. The cells are located on self-assembled hydroxyapatite patterns forming the tissue patterns and communicating via spatially propagating waves of calcium, sodium, and potassium ions. These waves result from positive feedback caused by the activation of Ca2+ channels. The fiber-based ion-selective microelectrodes fixed above the patterns are used to detect the sodium, potassium, calcium ion currents in the extracellular space. We use norepinephrine to activate the Ca2+ channels result in intracellular Ca2+ release between the cell communities on different patterns. This system could be perspective as an efficient platform to lab-on-a-chip study as well as fundamental understanding of cellular communication during regeneration.