Key Takeaways & Executive Findings
- •• • Flexoelectricity is markedly enhanced in ferroelectrics due to their large dielectric effect, enabling significant polarization under strain gradients, which is critical for micro- and nanoscale devices where piezoelectricity diminishes. • • Unlike piezoelectricity, flexoelectricity does not require an external electric field for polarization alignment, enhancing operational stability and mitigating issues such as aging, breakdown, and depolarization. • • Flexoelectricity is independent of unit cell symmetry, broadening the functional response of ferroelectric materials and providing a new physical mechanism for multi-scale regulation. • • The review highlights that flexoelectricity is typically much higher in micro- and nanostructures (e.g., thin films, nanowires) than in bulk, effectively overcoming the limitations of piezoelectricity at small dimensions.
Abstract
Flexoelectricity, the generation of electrical polarization in response to a strain gradient, is a fundamental electromechanical coupling mechanism that has gained significant attention due to its enhanced effects in ferroelectric materials, which exhibit large dielectric permittivities. This review comprehensively examines the classical theories and recent advances in flexoelectricity, with a primary focus on ferroelectric materials. We discuss the advantages and limitations of various characterization techniques, computational models for determining flexoelectric coefficients, and the mechanisms that enhance flexoelectricity in different ferroelectric systems. Furthermore, we explore the applications of flexoelectricity in devices, highlighting its potential to overcome the dimensional and stability limitations of piezoelectricity, particularly at the micro- and nanoscale. The review concludes by outlining future research directions, aiming to provide valuable insights for advancing both the fundamental science of flexoelectricity and the development of high-performance practical devices.
1. Introduction
The development of new energy technologies has become a central focus in global scientific research. Ferroelectric materials, characterized by spontaneous polarization and strong electromechanical coupling, show considerable potential for applications ranging from electronic devices to energy conversion systems. Piezoelectricity, a key property of such materials, facilitates mechanical-electrical energy conversion under uniform strain. However, its performance at the micro- and nanoscale sharply declines due to limitations in domain-switching mechanisms and structural constraints. Moreover, piezoelectricity requires an external electric field for polarization alignment, leading to stability issues such as aging, breakdown, and depolarization. These limitations create an urgent need for alternative electromechanical coupling mechanisms that can overcome structural, dimensional, and stability constraints.
Flexoelectricity, the generation of polarization under a strain gradient, offers a promising solution. It is typically much higher in micro- and nanostructures than in bulk, effectively overcoming the dimensional limitations of piezoelectricity. Additionally, flexoelectricity does not require an external electric field for polarization alignment, thereby enhancing operational stability. Importantly, flexoelectricity is independent of unit cell symmetry, broadening the functional response of ferroelectric materials and providing a new physical mechanism for their regulation across multiple scales. This review provides a comprehensive overview of flexoelectricity in ferroelectrics, covering classical theories, characterization techniques, computational models, enhancement mechanisms, and device applications, with the goal of guiding future research and development of high-performance micro- and nanoscale devices.
Loading authentic research manuscript (Pages 1–5)...
Darong Yu, Lei Shu, Zhiguo Wang, Zhibin Wen, Longlong Shu (2026). Flexoelectricity in Ferroelectrics: From Fundamentals to Applications. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3872-3
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What are the key advantages of flexoelectricity over piezoelectricity in ferroelectric materials, particularly at small scales?
Flexoelectricity is enhanced at micro- and nanoscales due to larger strain gradients, whereas piezoelectricity diminishes due to domain-switching limitations and structural constraints. Additionally, flexoelectricity does not require an external electric field for polarization alignment, reducing stability issues like aging and depolarization.
How does the independence of flexoelectricity from unit cell symmetry impact the design of ferroelectric devices?
This independence allows flexoelectricity to occur in all dielectric materials, not just those with non-centrosymmetric structures, broadening the range of materials that can be used for electromechanical applications. It also enables new mechanisms for regulating polarization across multiple scales.
What are the main challenges in characterizing flexoelectric coefficients in ferroelectric materials?
Challenges include separating flexoelectric contributions from other electromechanical effects, achieving accurate strain gradient measurements at small scales, and accounting for material-specific factors such as domain wall contributions and defect chemistry. Advanced techniques like scanning probe microscopy and dynamic mechanical analysis are often required.
What mechanisms are proposed to enhance flexoelectricity in ferroelectric materials?
Enhancement mechanisms include exploiting the large dielectric permittivity of ferroelectrics, engineering domain structures, introducing oxygen vacancies or defect dipoles, and utilizing compositional gradients. For example, Nb-doped BaTiO3 ceramics exhibit large flexoelectricity due to space-charge-induced colossal dielectric constant.
What are the potential applications of flexoelectricity in ferroelectric devices, and what are the practical limitations?
Potential applications include energy harvesting, sensing, actuation, and memory devices, particularly at the micro- and nanoscale. Practical limitations include the need for precise strain gradient control, material stability under repeated cycling, and integration challenges with existing technologies.
Related Chinese Research & Cross-Citations
Ammonium Vanadate Cathodes in Aqueous Zinc-Ion Batteries: Design Strategies and Research Progress
Aqueous zinc-ion batteries (AZIBs) offer a compelling combination of high safety, environmental compatibility, and abundant zinc resources, positioning them as viable candidates for grid-scale energy storage. Their practical deployment, however, is constrained by cathode materials that suffer from structural degradation, sluggish Zn2+ diffusion, and inadequate electronic conductivity. Ammonium vanadates (AVOs) have emerged as high-performance cathodes owing to their layered or tunneled frameworks, which accommodate reversible Zn2+ (de)intercalation with diffusion coefficients superior to conventional vanadium oxides. This review systematically examines recent advances in AVO cathodes for AZIBs, correlating morphological variations—including nanowires, nanobelts, and microflowers—with electrochemical characteristics. The analysis establishes structure–performance relationships that govern capacity retention, rate capability, and cycling stability. Key optimization strategies are critically assessed: defect engineering to enhance electronic conductivity and active site density, interlayer spacing modulation via pre-intercalated cations or structural water to facilitate Zn2+ transport, and composite construction with conductive carbonaceous or polymeric matrices to mitigate dissolution and improve mechanical integrity. Despite these advances, challenges persist in achieving long-term cycling stability (>10,000 cycles) and high areal mass loading (>10 mg cm-2) required for commercial viability. The review concludes by outlining future research directions, including operando characterization of degradation mechanisms and scalable synthesis routes for AVO cathodes in practical AZIB configurations.
Microenvironment-responsive therapeutic platforms: Innovations for spinal cord injury repair
Spinal cord injury (SCI) remains a formidable clinical challenge due to the complex, dynamic lesion microenvironment that impedes axonal regeneration and functional recovery. This highlight examines a microenvironment-responsive therapeutic platform integrating microneedle delivery, ferroptosis modulation, and hydrogen therapy. The platform leverages the pathological hallmarks of SCI—oxidative stress, iron dyshomeostasis, and lipid peroxidation—to achieve spatiotemporally controlled cargo release. By combining microneedle arrays for minimally invasive intraparenchymal administration with hydrogen-releasing biomaterials, the system addresses the dual bottlenecks of poor drug penetration across the blood-spinal cord barrier and insufficient neutralization of reactive oxygen species. Ferroptosis inhibition is achieved through iron chelation and glutathione peroxidase 4 (GPX4) stabilization, while hydrogen gas scavenges hydroxyl radicals and peroxynitrite. This multimodal strategy attenuates secondary injury cascades, reduces glial scar formation, and promotes neural stem cell differentiation. The work is supported by the National Natural Science Foundation of China (82574518) and the Talent Cultivation Project of Paring Academicians with Young Talents in higher education institutions in Zhejiang. The authors declare no conflict of interest. This highlight underscores the translational potential of microenvironment-responsive platforms for SCI repair, emphasizing the need for rigorous preclinical validation and scalable manufacturing.
Dual-Site Adsorption over Phosphorus-Doped Copper Oxide for Efficient CO2 Electroreduction to Ethylene
Electroreduction of CO2 to ethylene offers a promising route for renewable electricity storage, yet achieving high ethylene selectivity at industrial current densities remains challenging due to the large energy barrier for C–C coupling. Here, we report a “MOF-assisted in situ doping” strategy to introduce the oxophilic nonmetal phosphorus (P) into the copper oxide (CuO) lattice, constructing a localized Cu–P dual-site adsorption configuration for the key *OCCHO intermediate. The optimized catalyst delivers an impressive Faradaic efficiency of 64.6% for ethylene with a partial current density of 646 mA cm-2. Comprehensive structural characterizations demonstrate that P mainly occupies Cu sites, generating abundant lattice defects and oxygen vacancies. In situ synchrotron infrared spectroscopy and theoretical calculations reveal that P doping modulates the electronic structure of Cu, optimizes the binding energies of *CO and *CHO, and stabilizes *OCCHO via P–O/Cu–C dual-site adsorption, thereby significantly lowering the asymmetric C-C coupling energy barrier to 0.74 eV. This work highlights a dual-site microenvironment regulation strategy for CO2-to-ethylene electroreduction.
Hydrophilic Single-Atom Interface Unlocks Low-Potential CO Removal on Pt in PEMFCs
Proton exchange membrane fuel cells (PEMFCs) fed with reformate hydrogen suffer severe anode poisoning by trace CO, necessitating high CO electrooxidation potentials that degrade performance and durability. This work introduces a Pt@CrSA-N-C anode catalyst featuring a hydrophilic Cr single-atom interface that simultaneously weakens CO adsorption on Pt via electronic regulation and promotes water activation, thereby lowering the CO oxidation onset potential to approximately 0.13 V vs. RHE. The onset potential was determined by two independent methods: the first potential at which the background-corrected current exceeds 0 mA cm-2 during CO oxidation reaction tests in a three-electrode system, and the potential at which the forward scan current exceeds the N2 background current in CO-stripping voltammetry. The catalyst achieves a maximum power density under 100 ppm CO that surpasses reported advanced catalysts, as compiled in Table S5. Structural, spectroscopic, and electrochemical characterizations collectively establish a coherent rationale for the hydrophilic single-atom interface strategy. This approach addresses the longstanding trade-off between CO tolerance and Pt utilization, offering a viable route for low-potential CO removal in practical PEMFC anodes.
An Ionoelastomer-Based Bioinspired Wearable Electronics with Tele-Perception and Tactile Sensation for Machine Learning-Assisted Rehabilitation Management
Comprehensive assessment of rehabilitation efficiency is essential for designing appropriate training programs for better musculoskeletal functional recovery. Existing contact-receptor-dependent rehabilitation assessment systems mostly focus on assessing the restoration of muscle function by evaluating grip strength or joint flexion angle; however, parameters reflecting neuromuscular synergistic function are always overlooked. Herein, we develop an ionoelastomer-based soft artificial electroreceptor (SAER) that integrates tele-perception and tactile sensation to track the rehabilitation process, collecting signals related to approaching speed and grip strength sequentially. The SAER uses polyurethane ionoelastomer incorporated with quasi-solid conductive salt as the electric field receptor, and is integrated on a rehabilitation-training ball after assembly to establish an untethered detection device; this enables the remote capture of hand approaching parameter within a 9 cm range, followed by the quantification of grip strength when contacting and grasping. Furthermore, a data-driven assessment system is established by integrating machine learning, which accurately classifies rehabilitation efficiency into six levels; it supports for rehabilitation evaluation and training programs adjustment. Overall, the SAER-based rehabilitation management system establishes a paradigm that synergistically evaluating parameters corresponding to neuromuscular functional restoration and holds strong potential for home-based active rehabilitation for minimizing dependence on frequent clinical supervision.
Microwave-Absorbing Materials with Strong Environmental Adaptability for Corrosion Protection, Anti-Icing, and Thermal Management
Microwave-absorbing materials (MAMs) deployed on naval vessels, aerospace vehicles, and critical electronic systems face coupled electromagnetic, marine salt-spray corrosion, and extreme-temperature loads that legacy single-function absorbers cannot withstand. This review consolidates progress on three environmentally adaptive MAM classes: corrosion-protective, anti-icing, and thermal-management absorbers. The electromagnetic loss and impedance-matching fundamentals are first established, then the synergistic mechanisms, design strategies, and characterization protocols for each class are examined against representative material systems and their measured performance. The analysis identifies a shared design logic—multiscale hierarchical architecture, interfacial polarization engineering, and multifunctional phase integration—while distinguishing the divergent protection mechanisms: barrier and passivation effects for corrosion, surface-energy and latent-heat regulation for anti-icing, and phonon–electron transport decoupling for thermal management. Persistent bottlenecks include the trade-off between impedance matching and protective-layer density, the absence of standardized coupled-field test protocols, and the scarcity of long-term salt-spray and thermal-cycling durability data. Future directions are delineated: intelligent self-adaptive absorbers, multiphysics-coupled simulation frameworks, and environmentally benign multifunctional integration. The review provides a theoretical and technical basis for the design, construction, and engineering scale-up of next-generation high-performance absorbers for aerospace, electronic, and marine equipment.