Giant Photostriction Rate for Remote Opto-ultrasonic Structural Health Monitoring

Giant Photostriction Rate for Remote Opto-ultrasonic Structural Health Monitoring | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Giant Photostriction Rate for Remote Opto-ultrasonic Structural Health Monitoring Jie Yin, yuxuan yang, Xiaoming Shi, Chunlin Zhao, Cong Lin, Hong Tao, and 11 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7177986/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 24 Feb, 2026 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract Extending photocarrier lifetime, accelerating photostrictive strain buildup, and engaging more light–lattice interactions are key to improving bulk ferroelectric photostriction rate (coefficient integrating strain magnitude and generation speed, typically < 10⁻³ s⁻¹) for reliable remote ultrasound generation. We report non-poled terbium-doped (K,Na)NbO₃ ceramics (KNN-Tb), where Tb³⁺ 4 f -electron trapping prolongs photocarrier lifetime, enabling efficient carrier migration to domain walls for screening depolarization field. Hierarchical nanostructures—dense nanodomains (rapid local photostriction) and subwavelength grains (more light–lattice interactions and enhanced collective strain)—yield the photostriction rate of 6.41×10⁻¹ s⁻¹, two orders above conventional bulk ferroelectrics. Non-poled KNN-Tb avoids depoling issue, enabling robust opto-ultrasonic transducers that generate intense ultrasound under low-cost laser, demonstrated remote structural health monitoring. Our bulk ferroelectric design strategy enables cost-effective, high-performance remote opto-ultrasonic sensing technologies. Physical sciences/Materials science/Condensed-matter physics/Ferroelectrics and multiferroics Physical sciences/Optics and photonics/Optical materials and structures Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Elastic waves, governed fundamentally by coupled dynamic stress-strain relationships and wave-matter interactions, enable the dual transport of encoded acoustic information (via amplitude/phase modulation) and mechanical energy (through momentum transfer in viscoelastic media). These features establish their multidisciplinary utility in subwavelength non-destructive testing (NDT), in situ structural health monitoring (SHM), high-precision biosensing and targeted therapy, adaptive signal filtering, and solid-state wave-based computing paradigms 1 . Conventional systems for elastic wave generation and detection involve cables with the acoustic transducers, while remote operation without any wire connections is highly demanded to extend the use at inaccessible locations, minimize invasive mass and interference, and improve the system performance at reduced cost. Optomechanical energy conversion mechanism, which harnesses light-excited and controlled mechanical waves for actuation 2 – 4 , imaging 5 , 6 , sensing 7 , 8 , and quantum technologies 9 , 10 , presents a promising remote solution. Yet, its industrial adoption is hindered by low energy efficiency or slow strain generation, failing to meet high-strain-rate as required in high frequency ultrasound applications, such as ultrasonic detection 11 – 13 and photoacoustic imaging 14 , 15 . Optomechanical energy conversion occurs via three primary mechanisms: thermoelastic expansion 16 , 17 , molecular structural transitions 18 , 19 , and ferroelectric photostriction 20 – 22 . Thermoelastic expansion, though simple, exhibits extremely low efficiency (10 − 6 –10 − 8 ) 22 , 23 , requiring high-power pulsed lasers. Molecular phase transitions offer large strains (5–20%) but suffer from slow kinetics (strain rate ~ 10 − 5 s − 1 ) and irreversibility 24 – 29 , restricting high-frequency applications. Ferroelectric photostriction, driven by the separation of photo-generated carriers under internal electric field, offers a cost-effective approach for generating photo-induced strain under low-power illumination, through the converse piezoelectric response to charge redistribution (Fig. 1 a) 21 . While offering reversibility and precision, this mechanism is constrained by inefficient carrier migration (short photocarrier lifetime from rapid recombination) and slow photovoltage buildup process (milliseconds to seconds) across the poled sample and poor light penetration (~ tens of nm), collectively limiting the strain rate (coefficient integrating strain magnitude and generation speed, typically below 10⁻³ s⁻¹) of bulk ferroelectrics 22 . Consequently, the generated acoustic pressure remains too low for reliable ultrasonic wave production. Moreover, given the complexity of electrical polling and depoling issue over extended operation, photostriction in poled bulk ferroelectrics faces challenges for long-term remote opto-ultrasonic applications. Overcoming this limitation requires deeper light penetration to engage more grains in light–lattice interactions, and developing efficient localized optomechanical mechanisms within ferroelectric domains to accelerate and enhance the local photostriction without the need for poling treatment. Here, we show a hierarchical structural design strategy, to achieve a giant photostriction rate in bulk ferroelectrics. By tailoring sub-wavelength grain sizes to minimize Rayleigh scattering, we enhance optical penetration for maximizing light-lattice interactions and enhancing the collective photostriction (Fig. 1 b). Within these grains, nano-domain architectures are configured for enabling fast local photostriction. Phase-field simulations reveal that photo-induced carrier migration in properly nano-sized domains efficiently screens depolarization field at domain walls, generating local strains that can accumulate constructively into collective photostriction without poling treatment (Fig. 1 c). Moreover, we strategically introduce heavy terbium dopants (Tb 3+ ) to form electron traps via densely split 4 f -electron levels, prolonging carrier lifetimes, enhancing their migration efficiency toward domain walls, and thus boosting local photostriction amplitude (Fig. 1 d). A larger spontaneous polarization magnitude ( P mag ) facilitates photo-induced carrier separation, while a greater polarization angle deviation ( DP ) signifies reduced domain size 30 , collectively leading to enhanced local photostriction. In perovskite ABO₃ displacive ferroelectrics, spontaneous polarization ( P s ) primarily arises from the relative displacement of B-site cations against the oxygen octahedral center. To achieve a relatively large P mag while introducing strong random fields for a substantial DP , we employed A-site Tb 3+ doping. Leveraging these principles, we doped Tb³⁺ at A-sites within lead-free KNN ceramics- a widely studied and highly tunable ferroelectric platform—to simultaneously engineer grain size, domain architecture, and atomic-level structures as envisioned in our design. The resultant non-poled KNN-Tb ceramics exhibit a record-high photostriction rate of 6.41 × 10⁻¹ s⁻¹, two orders of magnitude higher than the reported ferroelectric photostriction in the literature, such as Pb(Mg₁/₃Nb₂/₃)O₃-PbTiO₃ (PMN-PT) and BiFeO₃ (BFO) single crystals. Atomic-scale structural analysis reveals underlying structural driving forces underlying the exceptional performance. Intensive ultrasonic waves were excited by light and reliable remote SHM function was demonstrated, using an opto-ultrasonic cantilever transducer made from the non-poled KNN-Tb. Crucially, the non-poled nature of KNN-Tb simplifies device fabrication, avoids depoling issues during prolonged operation, and enhances reliability and durability, marking a critical advancement toward next-generation opto-ultrasonic devices for practical applications. Enhanced Optical Transmittance and Enhanced Photostriction in KNN-Tb We optimized the fabrication process of KNN- x Tb ( x = 0, 0.01, 0.02, 0.03, 0.04) ceramics (Supplementary Methods 1.1), to prepare ferroelectric ceramics with reduced optical scattering and improved transmission in the visible light spectrum, and thus the samples show transparency. Representative samples ( x = 0.01, 0.02, 0.03) were selected to show their optical transmittance from 300 nm to 800 nm, as provided in Fig. 2 a. Specifically, the transmittance of KNN- x Tb ceramics at the 400 nm excitation wavelength were evaluated, revealing that the increased transmittance at this wavelength significantly boosts photo-induced photovoltage (Fig. 2 b and Supplementary Fig. S1 ). To eliminate compositional effects on the photovoltage, we analyzed the photovoltage of KNN-0.02Tb ceramics produced under varying processing conditions (Supplementary Fig. S2), revealing a proportional relationship between transmittance at the 400 nm excitation wavelength and photovoltage. Additionally, our investigations into photo-induced displacement of KNN- x Tb cantilevers, encompassing both poled and non-poled samples, demonstrated that non-poled samples can excite significant photo-induced displacement responses, as provided in Fig. 2 c. Notably, a maximum displacement of 202 nm was achieved with the non-poled KNN-0.02Tb cantilever, significantly exceeding that of a commercial PMN-PT cantilever (~ 3 nm) with the same size. The photostriction rate of up to 6.41 × 10 − 1 s − 1 were recorded for the KNN-0.02Tb cantilever (details in Supplementary Methods 1.2F, Supplementary Note 1 and Fig. S3), which is nearly two orders of magnitude higher than that in commercial PMN-PT single crystal cantilever (8.06 × 10 − 3 s − 1 ), as depicted in Fig. 2 d. Moreover, our KNN-0.02Tb ceramic sample exhibits robust water resistance, maintaining its photostriction performance even after 30 days of water immersion, as demonstrated by the cantilever with the same size fabricated from the immersed samples (Supplementary Fig. S4). Deciphering Structural Driving Force of Enhanced Photostriction in KNN-Tb The frequency-dependent electromechanical analysis (Supplementary Notes 2 and 3, Fig. S5) confirms that the large displacement and strain, observed in the KNN-Tb cantilever, originate from electromechanical resonance rather than thermal expansion (Supplementary Note 4 and Fig. S6), consistent with observations and conclusion in PMN-PT crystal cantilevers. To understand why the photostriction rate of KNN-Tb ceramics is two orders of magnitude higher than that of PMN-PT crystals, we analyzed the two key factors in photostriction rate calculation: resonance frequency and maximum deflected displacement of the cantilever (Supplementary Note 1). Compared to a PMN-PT crystal cantilever of the same dimensions and clamping conditions, the KNN-Tb ceramic cantilever exhibits a higher resonance frequency (9.1 kHz vs. 7.7 kHz), indicating a faster opto-mechanical response. Moreover, its maximum deflected displacement (220 nm) is significantly larger than that of the PMN-PT crystal cantilever (3 nm), leading to the obviously enhanced photostriction rate. To uncover the microscopic origin of this enhancement, we investigated the structural mechanisms governing the photostriction in KNN-Tb. While a recently proposed unit-cell polarization screening model predicts sub-picosecond photostriction in ferroelectrics 31 , our measurements reveal a microsecond-scale delay between peak illumination and maximum strain (Fig. S7), suggesting an obviously different underlying process. Instead, photo-induced carrier migration to local domain walls to screen the depolarization fields model appears to be applicable to our case, as supported by energy conversion analysis: the bulk photovoltaic effect (BPVE) efficiency η BPVE , and photostriction efficiency η photostriction , are 8.6 × 10 − 11 and 1.47 × 10 − 4 , respectively (Supplementary Note 5 and Fig. S8). While bulk photostriction theory limits η photostriction to η BPVE × η CPE (CPE is the converse piezoelectric effect), our results demonstrate that we have overcome this constraint through local opto-electromechanical coupling, manifested as local photostriction. This phenomenon is governed by (1) the magnitude of local electric field variations, driven by photo-induced charge carrier screening of the depolarization field, and (2) the strength of the local converse piezoelectric effect, determined by the intrinsic lattice properties of the material. Phase-field model incorporating charge carrier migration (Supplementary 2) reveal that optimized nanoscale domains (tens of nanometers) facilitate carrier migration toward domain walls (Fig. 3 a). Carrier accumulation at domain walls effectively screens bound charges, suppressing the depolarization field and strengthening the local electric field. However, at ultra-small domain sizes (a few nanometers), intensified random electric fields disrupt directional carrier migration to screen bound charges, diminishing the local electric field. Experimentally, excessive Tb doping enhances random fields, weakening the ability of photo-induced charge carriers to screen depolarization fields, thereby reducing the local piezoelectric response and ultimately diminishing photostrictive strain. Relaxor ferroelectrics, such as PMN-PT and (Bi 0.5 Na 0.5 )TiO 3 (BNT), exhibit strong random fields arising from substantial ionic valence and radius mismatches at the A/B sites 30 , 32 , 33 , which hinder effective charge screening and ultimately degrade photostrictive performance. In contrast, compositions with smaller ionic disparities, such as KNN (applied in this work) and BaTiO₃, are systems more suitable for achieving strong local photostriction. Future research could explore grain-domain-lattice engineering strategies to further enhance photostriction in these systems. Piezoelectric force microscopy (PFM) and switching spectroscopy PFM (SS-PFM) (Figs. S9, S10) confirm that appropriate Tb doping reduces domain size while enhancing the piezoelectric response up to x = 0.02, beyond which excessive doping suppresses ferroelectric polarization and dielectric permittivity (Fig. S11). As summarized in Fig. 3 b, the optimized local random fields induced by Tb doping maximize the local converse piezoelectric response. To uncover the structural mechanisms underlying photostriction enhancement, we performed a multiscale microstructural analysis of KNN-Tb ceramics. With the increasing Tb concentration, grain sizes were reduced to tens-to-hundreds of nanometers range (Fig. S12), smaller than the incident modulated light wavelength (400 nm). Within these sub-nano-sized grains, domain sizes ranged from a few to tens of nanometers (Fig. S9), more than one order of magnitude below the visible light wavelength. Consistent with our design strategy, the tailored small grain and domain architectures effectively suppress light scattering and enhance optical transmission, facilitating more light-lattice interactions and ultimately yielding greater collective photostriction. To further investigate the local structural effects of Tb doping, we employed (S)TEM to characterize KNN-0Tb and KNN-0.02Tb. In agreement with SEM and PFM results, TEM images (Figs. 3 c- 3 f) reveal a substantial reduction in both grain and domain sizes upon Tb incorporation. While rare-earth doping is a well-established strategy for tuning grain size and improving optical transparency in ferroelectric ceramics, its underlying mechanism for precisely and controllably modulating domain architecture remains unclear, posing a challenge for designing ferroelectrics with enhanced photostriction rate. To gain deeper insight into domain evolution, we conducted local polarization mapping (Figs. 3 g, 3 j), analyzed the impact of Tb doping on A-site cations (Figs. 3 h, 3 i, 3 k, 3 l), and performed atomic-scale stress mapping (Fig. S13) on KNN-0Tb and KNN-0.02Tb. Compared to the well-aligned polarization vectors in KNN-0Tb, KNN-0.02Tb exhibits reduced polarization coherence, forming nanoscale domains (< 10 nm) with small-angle domain walls. Consistent with phase-field simulations, smaller grains exhibit higher internal stress (Fig. S13), while increased Tb doping enhances local random fields (Fig. S14), leading to a domain sizreduction from the micrometer to nanometer scale, as observed in experiments and phase-field simulations (Fig. S15). To further uncover effective strategies for controlling local photostriction in bulk ferroelectrics, we explored the underlying structural driving forces for regulating ferroelectric domains. The composition-driven evolution of ferroelectric domains originates from changes in local spontaneous polarization, specifically, DP and P mag (Fig. 4 a). To uncover the atomic-scale driving forces for DP and P mag , we conducted a statistical correlation analysis linking these polarization parameters to key microstructural factors, including A-site cation variations (reflected by A-site cation intensity variations), oxygen octahedral tilt ( OT ), and oxygen octahedral distortion ( OD ). This analysis was based on atomic-scale mapping of these microstructural features, as provided in Figs. 4 b and 4 c (details can be seen in Supplementary Methods 1.3 and Figs. S16 and S17). Our analysis reveals a pronounced negative correlation between DP and P mag (Fig. 4 d), indicating that larger DP correspond to lower P mag . This interdependence suggests a mutually competitive relationship between DP and P mag . As provided in Figs. 4 e and 4 f, OT is correlated with DP , whereas OD is correlated with P mag . Given that large OD characterizes domain walls, increasing OT thus serves as the primary driving force for reducing domain size. In contrast, increasing OD acts as the main driving force in enhancing P mag . To further elucidate the driving forces of evolving OT and OD , we statistically analyzed variations in the relative lengths of A–O and B–O bonds and correlated them with OT and OD (Figs. 4 g and 4 h). Fluctuation in B–O bond lengths positively correlates with OD , whereas variation in A–O bond lengths correlates positively with OT . These insights suggest that compositional adjustments targeting A–O and B–O bonds modifications could effectively tune OD and OT , thus balancing the competition between DP and P mag . Under near-critical conditions, this strategy can achieve large DP while preserving relatively high P mag . In size-reduced domains, each domain retains a high P mag , promoting efficient migration of photo-induced charge carriers toward domain walls. These charge carriers shield bound charges at domain walls, reduce depolarization fields, and thus facilitate rapid and enhanced local photostriction. Correlation coefficients among these local structural factors were provided in Fig. 4 i, demonstrating the statistical reliability of our identified structural driving forces for modulating the domains. Opto-ultrasound Generation and Remote SHM via Photostriction We designed a remote ultrasonic SHM system enabled by the photostricton in KNN-0.02Tb, to monitor the damage status of engineering structures 34 . The system employs a KNN-0.02Tb optomechanical cantilever transducer with the size of 0.25 mm × 0.50 mm × 3.00 mm (width × height × length), bonded to a 1.6 mm-thick aluminum plate (selection details in Supplementary Note 7). When illuminated by continuous light modulated at 50.3 kHz corresponding to the resonance frequency of the coupled cantilever structure, the cantilever generates mechanical vibration due to photostriction in KNN-0.02Tb, exciting an ultrasonic wave propagating through the aluminum substrate. A laser scanning vibrometer captures the vibrational profiles, enabling real-time monitoring of defects, by analyzing amplitude and phase changes in the ultrasonic waves interacted with structural defects (Fig. 5 a). To assess reproducibility of this KNN-0.02Tb optomechanical transducer, cyclic on-off illumination tests were performed on it, with each "on" state inducing 500 electrical oscillations, repeated over seven on-off cycles (Fig. 5 b). The results confirm the cantilever’s reliability as an opto-mechanical transmitter. The system exhibited efficient wave coupling, producing ultrasonic signals with consistent periodicity (18.1 mm wavelength) and minimal attenuation across the pristine aluminum plate (Fig. 5 c). Damped sine wave fitting (R² >0.95) validated stable signal propagation, while spectral analysis confirmed frequency fidelity between the input modulation signals (50.3 kHz) and detected waveforms. The defect detection capability was evaluated using 4 mm × 22 mm strip defects of varying depths (0–1.6 mm), positioned 45 mm from the transmitter (Fig. S18). A 5-cycle, 3-V pp , 50.3 kHz sine wave was applied to modulate the illumination on the KNN-0.02Tb transmitter, generating a A0 Lamb ultrasonic wave 35 detected by the laser scanning vibrometer (see mode determination in Fig. S19). Signal attenuation exhibited a clear correlation with defect depth, while a normalized damage index (DI), derived from the amplitude comparison between pristine and defected states (see Supplementary Note 6), increased with the defect depth with consistent trend, until approaching the full plate thickness (Fig. 5 d). These experimental results demonstrate the feasibility of using the non-poled KNN-Tb ceramics for realizing remote opto-ultrasonic SHM in practical applications. Given the complexity of the poling process and depoling issue during long-term monitoring operation, using the non-poled KNN-Tb offers a cost-effective approach with improved robustness in manufacturing the next-generation optomechanical devices. In summary, we achieved an outstanding photostriction rate of 6.41 × 10⁻ 1 s − 1 in non-poled terbium-doped (K,Na)NbO₃ (KNN-Tb) ceramics, two orders of magnitude higher than typical ferroelectrics as previously reported in the literature. The exceptional photostriction performance results from enhanced coupling between the effective nanoscale photovoltaic effect and converse piezoelectric response, combined with optimized optical penetration in KNN-Tb ceramics, improving local photostriction and its constructive accumulation. Atomic-resolution analysis reveals that the heavy hetero-ions introduced at the A-site modulate metal-oxygen bond lengths, tailoring oxygen octahedral tilt ( OT ) and distortion ( OD ) level, and impact both the polarization angle deviation ( DP ) and magnitude ( P mag ). The competitive interplay between DP and P mag fosters optimal ferroelectric domain configuration that facilitates the migration of photo-induced carriers to domain walls, leading to the large and rapid local photostriction. Optimized optical penetration facilitates more grain participation in light–lattice interactions, promoting greater accumulation of local photostriction and enhancing the collective photostriction. Intensive ultrasonic waves have been excited by light and remote ultrasonic SHM function has been demonstrated, using an opto-ultrasonic cantilever transducer made from the KNN-Tb ceramics. Our research outcome here illustrates a versatile approach for engineering multiscale structures in bulk ferroelectrics, enabling giant photostriction rate for next-generation opto-acoustic devices innovation, and provides a unique technical solution for remote opto-ultrasound applications. Methods See details of methods part in supplementary information files. Declarations Competing interests The authors declare no conflict of interest. Author Contributions The work was designed and guided by J. Y., H. W., J. W., and K. Y. Material selection, material fabrication by J. Y., H. T., C. Z. and C. L. Device design, improvement and testing by J. Y. The ultrasonic data processing and analysis were done by J. Y. X. S. conducted phase-field simulations. H. T. and J. Y. conducted the PFM characterization and analysis. H. W. and Y. Y. conducted the (S)TEM characterization and analysis. D. B. K. L. provided technical support for device fabrication and optimization. L. L. and Y. S. provided technical discussions on the acoustic wave characterization by using the laser scanning vibrometer. J. Y., H. W., F. L., K.Y. and J. W. summarized and analyzed the data, and discussed the results. All authors contributed to discussing and writing the manuscript. Acknowledgements The authors acknowledge the research grant supported by National Key R&D Program of China (2021YFB3201100), A*STAR-RIE2020 AME Industry Alignment Fund–Pre-positioning Programme (IAF-PP) (grant no. A20F5a0043), AME Programmatic Fund (Grant No. A20G9b0135), and IAF311014R, and by the National Natural Science Foundation of China (U23A20567, 2172128, 52172128 and 52472250). The authors acknowledge the technical support and discussions from TaiHang Laboratory and Zhejiang Shunhui Optical Technology Co., Ltd. Data availability The data corresponding to this study are available from the first author and corresponding authors upon request. Code availability MATLAB scripts are available from the first author and corresponding authors upon request. References Chaikin PM, Lubensky TC, Witten TA (1995) Principles of condensed matter physics . 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Supplementary Files SupportingMaterials.docx The supporting materials of the whole photostriction work AreaScanRepresentativeExample.mp4 Representative example of this photostriction work Cite Share Download PDF Status: Published Journal Publication published 24 Feb, 2026 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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Yin","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6UlEQVRIie3RsWvCQBTH8QsHl+WnodtJ+y8UHgjR4dB/JRC4KYOjoyDoIrra/6J/QtKHcUnp6uCgFDpn7NChZm7J6eZwn/m+HO89ITzvHsnofEqmGlG4OeU1mZE7CSGprsxTb1UFxXZiU3cSQT28LKyhQyYZ9VswcxXP804pUTFE9Z6zoVyKkHevbUnMXfuJKSNYrhPO6NgVsPbQnohBv/lFIqdL8iWFRuxK4sfOgqF0QjwkDmbuBHHvMj6gM2JxXaLSZsnQKJNiRTZVzlk+uGhOOR7v51x//5hRFHLZmvylbnvueZ7n/ecXkblRaTb8TSQAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-9024-6324","institution":"Sichuan University","correspondingAuthor":true,"prefix":"","firstName":"Jie","middleName":"","lastName":"Yin","suffix":""},{"id":500243478,"identity":"a0b01576-ba68-448c-a88a-e11cf7c94742","order_by":1,"name":"yuxuan yang","email":"","orcid":"https://orcid.org/0009-0008-3700-612X","institution":"Xi'an Jiaotong University, Xi'an","correspondingAuthor":false,"prefix":"","firstName":"yuxuan","middleName":"","lastName":"yang","suffix":""},{"id":500243479,"identity":"43db4dcd-6846-44db-b535-00e9049abe55","order_by":2,"name":"Xiaoming Shi","email":"","orcid":"https://orcid.org/0000-0001-7332-6835","institution":"University of Science and Technology Beijing","correspondingAuthor":false,"prefix":"","firstName":"Xiaoming","middleName":"","lastName":"Shi","suffix":""},{"id":500243480,"identity":"d90d2849-beca-4686-b571-78d9a5c9830d","order_by":3,"name":"Chunlin Zhao","email":"","orcid":"https://orcid.org/0000-0003-1333-1864","institution":"Fuzhou University","correspondingAuthor":false,"prefix":"","firstName":"Chunlin","middleName":"","lastName":"Zhao","suffix":""},{"id":500243481,"identity":"3603334e-934f-4ed8-8baa-2862b3514a59","order_by":4,"name":"Cong Lin","email":"","orcid":"","institution":"Fuzhou University","correspondingAuthor":false,"prefix":"","firstName":"Cong","middleName":"","lastName":"Lin","suffix":""},{"id":500243482,"identity":"176c56d2-4557-4a6e-a967-067142a2efae","order_by":5,"name":"Hong Tao","email":"","orcid":"","institution":"Southwest Minzu University","correspondingAuthor":false,"prefix":"","firstName":"Hong","middleName":"","lastName":"Tao","suffix":""},{"id":500243483,"identity":"f0906ec3-5cc1-4da1-ae49-2dfedfbbfbb6","order_by":6,"name":"David Lim","email":"","orcid":"https://orcid.org/0000-0001-6046-469X","institution":"Institute of Materials Research and Engineering","correspondingAuthor":false,"prefix":"","firstName":"David","middleName":"","lastName":"Lim","suffix":""},{"id":500243484,"identity":"1bba679e-1636-4517-a0c4-fce9fe5cc0cc","order_by":7,"name":"Chao Jiang","email":"","orcid":"","institution":"Institute of Materials Research and Engineering","correspondingAuthor":false,"prefix":"","firstName":"Chao","middleName":"","lastName":"Jiang","suffix":""},{"id":500243485,"identity":"21883e58-8f3e-4a9a-9a52-1a6a2efb556f","order_by":8,"name":"Liming Lei","email":"","orcid":"https://orcid.org/0000-0001-5146-7987","institution":"TaiHang Laboratory","correspondingAuthor":false,"prefix":"","firstName":"Liming","middleName":"","lastName":"Lei","suffix":""},{"id":500243486,"identity":"10c2bd84-0a7c-4e76-bff0-a05beeca0f0c","order_by":9,"name":"Yunfeng Song","email":"","orcid":"","institution":"Zhejiang Shunhui Optical Technology Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Yunfeng","middleName":"","lastName":"Song","suffix":""},{"id":500243487,"identity":"606ed135-8d31-4430-b379-810af793d800","order_by":10,"name":"Yang Zhang","email":"","orcid":"","institution":"Xi’an Jiaotong University","correspondingAuthor":false,"prefix":"","firstName":"Yang","middleName":"","lastName":"Zhang","suffix":""},{"id":500243488,"identity":"87862f32-9e25-4641-b290-652b611565b7","order_by":11,"name":"Xiangdong Ding","email":"","orcid":"","institution":"Xi’an Jiaotong University","correspondingAuthor":false,"prefix":"","firstName":"Xiangdong","middleName":"","lastName":"Ding","suffix":""},{"id":500243489,"identity":"9b13300b-6ee3-4c2f-96e3-306db2c20441","order_by":12,"name":"Jun Sun","email":"","orcid":"https://orcid.org/0000-0002-6796-5777","institution":"Xi’an Jiaotong University","correspondingAuthor":false,"prefix":"","firstName":"Jun","middleName":"","lastName":"Sun","suffix":""},{"id":500243490,"identity":"a9db25f4-7ac9-4ee5-b8e9-5a145f309b71","order_by":13,"name":"Fei Li","email":"","orcid":"https://orcid.org/0000-0002-4572-0322","institution":"Xi'an Jiaotong University","correspondingAuthor":false,"prefix":"","firstName":"Fei","middleName":"","lastName":"Li","suffix":""},{"id":500243491,"identity":"1f8fdce4-7321-49fe-b22c-79cde94b8b42","order_by":14,"name":"Haijun Wu","email":"","orcid":"https://orcid.org/0000-0002-7303-379X","institution":"Xi'an Jiaotong University","correspondingAuthor":false,"prefix":"","firstName":"Haijun","middleName":"","lastName":"Wu","suffix":""},{"id":500243492,"identity":"2aba515d-91aa-497d-b1aa-ff265dbf9d0b","order_by":15,"name":"Jiagang Wu","email":"","orcid":"","institution":"Sichuan University","correspondingAuthor":false,"prefix":"","firstName":"Jiagang","middleName":"","lastName":"Wu","suffix":""},{"id":500243493,"identity":"a20e3766-3691-47a9-b621-cccb05288c6f","order_by":16,"name":"Kui Yao","email":"","orcid":"https://orcid.org/0000-0001-5875-4815","institution":"Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research)","correspondingAuthor":false,"prefix":"","firstName":"Kui","middleName":"","lastName":"Yao","suffix":""}],"badges":[],"createdAt":"2025-07-21 13:26:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7177986/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7177986/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41467-026-69906-y","type":"published","date":"2026-02-24T05:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":89253695,"identity":"e4504075-c1f8-4a2e-82dc-9d4ab2896597","added_by":"auto","created_at":"2025-08-18 04:47:24","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":2445846,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHierarchical design strategy for enhancing the photostriction rate in bulk ferroelectrics. a\u003c/strong\u003e, Schematic of photostriction in ferroelectrics. Photo-induced carrier migration under the spontaneous polarization aligned internal electric field, enables photo-induced strain via the converse piezoelectric response to charge redistribution. \u003cstrong\u003eb\u003c/strong\u003e, Grain-level design to enhance light-lattice interactions. Large grains scatter light at grain boundaries, reducing transmittance. Decreasing grain size below the light wavelength minimizes scattering, improving light penetration, and enhances light-lattice interaction. \u003cstrong\u003ec\u003c/strong\u003e, Domain-level design for rapid local photostriction. Phase-field simulations incorporating carrier migration within domains reveal optimized domain size for enhancing local photostriction in bulk ferroelectrics. \u003cstrong\u003ed\u003c/strong\u003e, Atomic-level design for prolonged carrier lifetime and efficient carrier migration to domain walls. Rare-earth (RE) element terbium (Tb) is introduced as the donor dopant, to create optimal electron traps via densely split 4\u003cem\u003ef\u003c/em\u003e-electron levels. These traps extend carrier lifetime and facilitate migration toward domain walls, enhancing local photostriction.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-7177986/v1/3bd96621be9ddc60ab89b59b.png"},{"id":89253691,"identity":"9cb0b3c6-fa64-4e3d-a20b-c43e9f4f4957","added_by":"auto","created_at":"2025-08-18 04:47:23","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1129815,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEnhanced optomechanical coupling in KNN-Tb ceramics. a\u003c/strong\u003e, Optical transmittance of KNN-\u003cem\u003ex\u003c/em\u003eTb ceramics (\u003cem\u003ex\u003c/em\u003e=0-0.03) across the 300 nm to 800 nm wavelength range. \u003cstrong\u003eb\u003c/strong\u003e, Comparison of transmittance and photovoltage in KNN-\u003cem\u003ex\u003c/em\u003eTb (\u003cem\u003ex\u003c/em\u003e=0-0.03) ceramics, under modulated light with 400 nm wavelength. \u003cstrong\u003ec\u003c/strong\u003e, Photo-induced displacement in poled and non-poled KNN-\u003cem\u003ex\u003c/em\u003eTb (\u003cem\u003ex\u003c/em\u003e=0-0.03) ceramic cantilevers, under modulated light with 400 nm wavelength. \u003cstrong\u003ed\u003c/strong\u003e, Maximum strain and strain rate across representative photostrictive materials, showcasing the substantially enhanced photostrictive strain and strain rate in non-poled KNN-0.02Tb ceramics.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-7177986/v1/8bc781bb987acbcc8d8bb6a4.png"},{"id":89253692,"identity":"317f690f-3eca-4446-a208-5018dd422e73","added_by":"auto","created_at":"2025-08-18 04:47:23","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":802923,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEnhanced optomechanical coupling in KNN-Tb ceramics. \u003c/strong\u003e. \u003cstrong\u003ea\u003c/strong\u003e, Relationship between ferroelectric domain sizes and the concentration of photo-induced charge carriers on domain walls and the local piezoelectricity. The data were depicted as a function of domain size, derived from phase-field simulations on a photo-induced charge carrier diffusion model within local ferroelectric domains. \u003cstrong\u003eb\u003c/strong\u003e, Local piezoelectric responses of KNN-\u003cem\u003ex\u003c/em\u003eTb ceramics under large (20 V) and small (5 V) driving voltage conditions. Data were subtracted from the local switching spectroscopic PFM results. \u003cstrong\u003ec-f\u003c/strong\u003e, Grain and domain morphologies of KNN-0Tb and KNN-0.02Tb. \u003cstrong\u003eg-l\u003c/strong\u003e, Local polarization mapping and doping effect on A-site analysis on KNN-0Tb and KNN-0.02Tb samples.\u003c/p\u003e","description":"","filename":"image3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7177986/v1/54a6af6376f47c77d468f24e.jpeg"},{"id":89254297,"identity":"df9e6e1e-f901-49bf-b12e-affff7fc2f2c","added_by":"auto","created_at":"2025-08-18 04:55:24","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2451522,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eStructural driving force analysis for uncovering effective strategies to control photostriction in KNN-Tb. a\u003c/strong\u003e, Grain and domain morphologies of KNN-\u003cem\u003ex\u003c/em\u003eTb. \u003cstrong\u003eb\u003c/strong\u003e, \u003cstrong\u003ec,\u003c/strong\u003e Key structural features and dominant driving forces governing domain evolution in perovskite materials. \u003cstrong\u003ed\u003c/strong\u003e, Correlation between polarization magnitude (\u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e) and polarization angle deviation (\u003cem\u003eDP\u003c/em\u003e). \u003cstrong\u003ee\u003c/strong\u003e, Correlation among A-site cation intensity (\u003cem\u003eI\u003c/em\u003e\u003csub\u003eA-site\u003c/sub\u003e), oxygen octahedral tilt (\u003cem\u003eOT\u003c/em\u003e), distortion (\u003cem\u003eOD\u003c/em\u003e) and \u003cem\u003eDP\u003c/em\u003e. \u003cstrong\u003ef\u003c/strong\u003e, Correlation among \u003cem\u003eI\u003c/em\u003e\u003csub\u003eA-site\u003c/sub\u003e, \u003cem\u003eOT\u003c/em\u003e, \u003cem\u003eOD\u003c/em\u003e and \u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e. \u003cstrong\u003eg\u003c/strong\u003e, Correlation between relative A-O (\u003cem\u003eLAO\u003c/em\u003e) and B-O (\u003cem\u003eLBO\u003c/em\u003e) bond lengths and \u003cem\u003eOD\u003c/em\u003e. \u003cstrong\u003eh\u003c/strong\u003e, Correlation between\u003cem\u003e LAO\u003c/em\u003e and \u003cem\u003eLBO\u003c/em\u003e and \u003cem\u003eOT\u003c/em\u003e. \u003cstrong\u003ei\u003c/strong\u003e, Degree of interdependence among local driving forces.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-7177986/v1/78de8685412b7353326bd1a6.png"},{"id":89253697,"identity":"4222b3a7-80e2-4676-909a-8c6ec4b79cc4","added_by":"auto","created_at":"2025-08-18 04:47:24","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2052163,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOpto-ultrasound generation and remote SHM by photostriction in non-poled KNN-Tb ceramics. a, \u003c/strong\u003eSchematic of the remote ultrasonic SHM enabled by photostriction. Modulated light in continuous mode excites the KNN-\u003cem\u003ex\u003c/em\u003eTb cantilever that acts as an opto-ultrasonic transmitter, generating vibrations for exciting the ultrasound in the aluminum plate. The laser scanning vibrometer detects ultrasonic waves, with amplitude and phase of which indicating the location and size of structural defects in the aluminum plate. \u003cstrong\u003eb, \u003c/strong\u003eReproducibility of the vibrations in the KNN-xTb cantilever, confirming its reliability as an ultrasonic transmitter. \u003cstrong\u003ec, \u003c/strong\u003eUltrasonic wave propagation in the aluminum plate, excited by the cantilever’s vibrations. The wave profile follows a damped sine function.\u003cstrong\u003e d, \u003c/strong\u003eDetection of defects with varying depths, demonstrating remote opto-ultrasonic SHM function.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-7177986/v1/9c753d38a7598456379da506.png"},{"id":105984142,"identity":"61222431-a5a5-4809-9349-bf1c5ea08005","added_by":"auto","created_at":"2026-04-02 07:13:17","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":8991857,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7177986/v1/faabba2f-847c-46e3-a59f-d8e743b7a3e2.pdf"},{"id":89253693,"identity":"5d7bf296-bb27-49a9-bed0-0e9730f8575c","added_by":"auto","created_at":"2025-08-18 04:47:24","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":10213656,"visible":true,"origin":"","legend":"The supporting materials of the whole photostriction work","description":"","filename":"SupportingMaterials.docx","url":"https://assets-eu.researchsquare.com/files/rs-7177986/v1/545f9f6e0f3e0301303d5379.docx"},{"id":89253699,"identity":"38a34233-cc2b-420f-9b57-63dddef67006","added_by":"auto","created_at":"2025-08-18 04:47:24","extension":"mp4","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":6831364,"visible":true,"origin":"","legend":"Representative example of this photostriction work","description":"","filename":"AreaScanRepresentativeExample.mp4","url":"https://assets-eu.researchsquare.com/files/rs-7177986/v1/98800ed633117f855207a521.mp4"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Giant Photostriction Rate for Remote Opto-ultrasonic Structural Health Monitoring","fulltext":[{"header":"Introduction","content":"\u003cp\u003eElastic waves, governed fundamentally by coupled dynamic stress-strain relationships and wave-matter interactions, enable the dual transport of encoded acoustic information (via amplitude/phase modulation) and mechanical energy (through momentum transfer in viscoelastic media). These features establish their multidisciplinary utility in subwavelength non-destructive testing (NDT), in situ structural health monitoring (SHM), high-precision biosensing and targeted therapy, adaptive signal filtering, and solid-state wave-based computing paradigms\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Conventional systems for elastic wave generation and detection involve cables with the acoustic transducers, while remote operation without any wire connections is highly demanded to extend the use at inaccessible locations, minimize invasive mass and interference, and improve the system performance at reduced cost. Optomechanical energy conversion mechanism, which harnesses light-excited and controlled mechanical waves for actuation\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e, imaging\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e, sensing\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e, and quantum technologies\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e, presents a promising remote solution. Yet, its industrial adoption is hindered by low energy efficiency or slow strain generation, failing to meet high-strain-rate as required in high frequency ultrasound applications, such as ultrasonic detection\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e and photoacoustic imaging\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eOptomechanical energy conversion occurs via three primary mechanisms: thermoelastic expansion\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e, molecular structural transitions\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e, and ferroelectric photostriction\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Thermoelastic expansion, though simple, exhibits extremely low efficiency (10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u0026ndash;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e) \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, requiring high-power pulsed lasers. Molecular phase transitions offer large strains (5\u0026ndash;20%) but suffer from slow kinetics (strain rate\u0026thinsp;~\u0026thinsp;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and irreversibility\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e, restricting high-frequency applications. Ferroelectric photostriction, driven by the separation of photo-generated carriers under internal electric field, offers a cost-effective approach for generating photo-induced strain under low-power illumination, through the converse piezoelectric response to charge redistribution (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea)\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. While offering reversibility and precision, this mechanism is constrained by inefficient carrier migration (short photocarrier lifetime from rapid recombination) and slow photovoltage buildup process (milliseconds to seconds) across the poled sample and poor light penetration (~\u0026thinsp;tens of nm), collectively limiting the strain rate (coefficient integrating strain magnitude and generation speed, typically below 10⁻\u0026sup3; s⁻\u0026sup1;) of bulk ferroelectrics\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Consequently, the generated acoustic pressure remains too low for reliable ultrasonic wave production. Moreover, given the complexity of electrical polling and depoling issue over extended operation, photostriction in poled bulk ferroelectrics faces challenges for long-term remote opto-ultrasonic applications. Overcoming this limitation requires deeper light penetration to engage more grains in light\u0026ndash;lattice interactions, and developing efficient localized optomechanical mechanisms within ferroelectric domains to accelerate and enhance the local photostriction without the need for poling treatment.\u003c/p\u003e\n\u003cp\u003eHere, we show a hierarchical structural design strategy, to achieve a giant photostriction rate in bulk ferroelectrics. By tailoring sub-wavelength grain sizes to minimize Rayleigh scattering, we enhance optical penetration for maximizing light-lattice interactions and enhancing the collective photostriction (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eb). Within these grains, nano-domain architectures are configured for enabling fast local photostriction. Phase-field simulations reveal that photo-induced carrier migration in properly nano-sized domains efficiently screens depolarization field at domain walls, generating local strains that can accumulate constructively into collective photostriction without poling treatment (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ec). Moreover, we strategically introduce heavy terbium dopants (Tb\u003csup\u003e3+\u003c/sup\u003e) to form electron traps via densely split 4\u003cem\u003ef\u003c/em\u003e-electron levels, prolonging carrier lifetimes, enhancing their migration efficiency toward domain walls, and thus boosting local photostriction amplitude (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ed). A larger spontaneous polarization magnitude (\u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e) facilitates photo-induced carrier separation, while a greater polarization angle deviation (\u003cem\u003eDP\u003c/em\u003e) signifies reduced domain size\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e, collectively leading to enhanced local photostriction. In perovskite ABO₃ displacive ferroelectrics, spontaneous polarization (\u003cem\u003eP\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e) primarily arises from the relative displacement of B-site cations against the oxygen octahedral center. To achieve a relatively large \u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e while introducing strong random fields for a substantial \u003cem\u003eDP\u003c/em\u003e, we employed A-site \u003cstrong\u003eTb\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e3+\u003c/strong\u003e\u003c/sup\u003e doping.\u003c/p\u003e\n\u003cp\u003eLeveraging these principles, we doped Tb\u0026sup3;⁺ at A-sites within lead-free KNN ceramics- a widely studied and highly tunable ferroelectric platform\u0026mdash;to simultaneously engineer grain size, domain architecture, and atomic-level structures as envisioned in our design. The resultant non-poled KNN-Tb ceramics exhibit a record-high photostriction rate of 6.41 \u0026times; 10⁻\u0026sup1; s⁻\u0026sup1;, two orders of magnitude higher than the reported ferroelectric photostriction in the literature, such as Pb(Mg₁/₃Nb₂/₃)O₃-PbTiO₃ (PMN-PT) and BiFeO₃ (BFO) single crystals. Atomic-scale structural analysis reveals underlying structural driving forces underlying the exceptional performance. Intensive ultrasonic waves were excited by light and reliable remote SHM function was demonstrated, using an opto-ultrasonic cantilever transducer made from the non-poled KNN-Tb. Crucially, the non-poled nature of KNN-Tb simplifies device fabrication, avoids depoling issues during prolonged operation, and enhances reliability and durability, marking a critical advancement toward next-generation opto-ultrasonic devices for practical applications.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEnhanced Optical Transmittance and Enhanced Photostriction in KNN-Tb\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe optimized the fabrication process of KNN-\u003cem\u003ex\u003c/em\u003eTb (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0, 0.01, 0.02, 0.03, 0.04) ceramics (Supplementary Methods 1.1), to prepare ferroelectric ceramics with reduced optical scattering and improved transmission in the visible light spectrum, and thus the samples show transparency. Representative samples (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.01, 0.02, 0.03) were selected to show their optical transmittance from 300 nm to 800 nm, as provided in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ea. Specifically, the transmittance of KNN-\u003cem\u003ex\u003c/em\u003eTb ceramics at the 400 nm excitation wavelength were evaluated, revealing that the increased transmittance at this wavelength significantly boosts photo-induced photovoltage (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eb and Supplementary Fig. \u003cspan class=\"InternalRef\"\u003eS1\u003c/span\u003e). To eliminate compositional effects on the photovoltage, we analyzed the photovoltage of KNN-0.02Tb ceramics produced under varying processing conditions (Supplementary Fig. S2), revealing a proportional relationship between transmittance at the 400 nm excitation wavelength and photovoltage.\u003c/p\u003e\n\u003cp\u003eAdditionally, our investigations into photo-induced displacement of KNN-\u003cem\u003ex\u003c/em\u003eTb cantilevers, encompassing both poled and non-poled samples, demonstrated that non-poled samples can excite significant photo-induced displacement responses, as provided in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ec. Notably, a maximum displacement of 202 nm was achieved with the non-poled KNN-0.02Tb cantilever, significantly exceeding that of a commercial PMN-PT cantilever (~\u0026thinsp;3 nm) with the same size. The photostriction rate of up to 6.41 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e were recorded for the KNN-0.02Tb cantilever (details in Supplementary Methods 1.2F, Supplementary Note 1 and Fig. S3), which is nearly two orders of magnitude higher than that in commercial PMN-PT single crystal cantilever (8.06 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), as depicted in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ed. Moreover, our KNN-0.02Tb ceramic sample exhibits robust water resistance, maintaining its photostriction performance even after 30 days of water immersion, as demonstrated by the cantilever with the same size fabricated from the immersed samples (Supplementary Fig. S4).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeciphering Structural Driving Force of Enhanced Photostriction in KNN-Tb\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe frequency-dependent electromechanical analysis (Supplementary Notes 2 and 3, Fig. S5) confirms that the large displacement and strain, observed in the KNN-Tb cantilever, originate from electromechanical resonance rather than thermal expansion (Supplementary Note 4 and Fig. S6), consistent with observations and conclusion in PMN-PT crystal cantilevers. To understand why the photostriction rate of KNN-Tb ceramics is two orders of magnitude higher than that of PMN-PT crystals, we analyzed the two key factors in photostriction rate calculation: resonance frequency and maximum deflected displacement of the cantilever (Supplementary Note 1). Compared to a PMN-PT crystal cantilever of the same dimensions and clamping conditions, the KNN-Tb ceramic cantilever exhibits a higher resonance frequency (9.1 kHz \u003cem\u003evs.\u003c/em\u003e 7.7 kHz), indicating a faster opto-mechanical response. Moreover, its maximum deflected displacement (220 nm) is significantly larger than that of the PMN-PT crystal cantilever (3 nm), leading to the obviously enhanced photostriction rate.\u003c/p\u003e\n\u003cp\u003eTo uncover the microscopic origin of this enhancement, we investigated the structural mechanisms governing the photostriction in KNN-Tb. While a recently proposed unit-cell polarization screening model predicts sub-picosecond photostriction in ferroelectrics\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e, our measurements reveal a microsecond-scale delay between peak illumination and maximum strain (Fig. S7), suggesting an obviously different underlying process. Instead, photo-induced carrier migration to local domain walls to screen the depolarization fields model appears to be applicable to our case, as supported by energy conversion analysis: the bulk photovoltaic effect (BPVE) efficiency \u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eBPVE\u003c/sub\u003e, and photostriction efficiency \u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003ephotostriction\u003c/sub\u003e, are 8.6 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;11\u003c/sup\u003e and 1.47 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e, respectively (Supplementary Note 5 and Fig. S8). While bulk photostriction theory limits \u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003ephotostriction\u003c/sub\u003e to \u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eBPVE\u003c/sub\u003e\u0026thinsp;\u0026times;\u0026thinsp;\u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eCPE\u003c/sub\u003e (CPE is the converse piezoelectric effect), our results demonstrate that we have overcome this constraint through local opto-electromechanical coupling, manifested as local photostriction. This phenomenon is governed by (1) the magnitude of local electric field variations, driven by photo-induced charge carrier screening of the depolarization field, and (2) the strength of the local converse piezoelectric effect, determined by the intrinsic lattice properties of the material.\u003c/p\u003e\n\u003cp\u003ePhase-field model incorporating charge carrier migration (Supplementary 2) reveal that optimized nanoscale domains (tens of nanometers) facilitate carrier migration toward domain walls (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ea). Carrier accumulation at domain walls effectively screens bound charges, suppressing the depolarization field and strengthening the local electric field. However, at ultra-small domain sizes (a few nanometers), intensified random electric fields disrupt directional carrier migration to screen bound charges, diminishing the local electric field. Experimentally, excessive Tb doping enhances random fields, weakening the ability of photo-induced charge carriers to screen depolarization fields, thereby reducing the local piezoelectric response and ultimately diminishing photostrictive strain. Relaxor ferroelectrics, such as PMN-PT and (Bi\u003csub\u003e0.5\u003c/sub\u003eNa\u003csub\u003e0.5\u003c/sub\u003e)TiO\u003csub\u003e3\u003c/sub\u003e (BNT), exhibit strong random fields arising from substantial ionic valence and radius mismatches at the A/B sites\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e, which hinder effective charge screening and ultimately degrade photostrictive performance. In contrast, compositions with smaller ionic disparities, such as KNN (applied in this work) and BaTiO₃, are systems more suitable for achieving strong local photostriction. Future research could explore grain-domain-lattice engineering strategies to further enhance photostriction in these systems. Piezoelectric force microscopy (PFM) and switching spectroscopy PFM (SS-PFM) (Figs. S9, S10) confirm that appropriate Tb doping reduces domain size while enhancing the piezoelectric response up to \u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.02, beyond which excessive doping suppresses ferroelectric polarization and dielectric permittivity (Fig. S11). As summarized in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eb, the optimized local random fields induced by Tb doping maximize the local converse piezoelectric response.\u003c/p\u003e\n\u003cp\u003eTo uncover the structural mechanisms underlying photostriction enhancement, we performed a multiscale microstructural analysis of KNN-Tb ceramics. With the increasing Tb concentration, grain sizes were reduced to tens-to-hundreds of nanometers range (Fig. S12), smaller than the incident modulated light wavelength (400 nm). Within these sub-nano-sized grains, domain sizes ranged from a few to tens of nanometers (Fig. S9), more than one order of magnitude below the visible light wavelength. Consistent with our design strategy, the tailored small grain and domain architectures effectively suppress light scattering and enhance optical transmission, facilitating more light-lattice interactions and ultimately yielding greater collective photostriction. To further investigate the local structural effects of Tb doping, we employed (S)TEM to characterize KNN-0Tb and KNN-0.02Tb. In agreement with SEM and PFM results, TEM images (Figs. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ec-\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ef) reveal a substantial reduction in both grain and domain sizes upon Tb incorporation. While rare-earth doping is a well-established strategy for tuning grain size and improving optical transparency in ferroelectric ceramics, its underlying mechanism for precisely and controllably modulating domain architecture remains unclear, posing a challenge for designing ferroelectrics with enhanced photostriction rate.\u003c/p\u003e\n\u003cp\u003eTo gain deeper insight into domain evolution, we conducted local polarization mapping (Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eg, \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ej), analyzed the impact of Tb doping on A-site cations (Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eh, \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ei, \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ek, \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003el), and performed atomic-scale stress mapping (Fig. S13) on KNN-0Tb and KNN-0.02Tb. Compared to the well-aligned polarization vectors in KNN-0Tb, KNN-0.02Tb exhibits reduced polarization coherence, forming nanoscale domains (\u0026lt;\u0026thinsp;10 nm) with small-angle domain walls. Consistent with phase-field simulations, smaller grains exhibit higher internal stress (Fig. S13), while increased Tb doping enhances local random fields (Fig. S14), leading to a domain sizreduction from the micrometer to nanometer scale, as observed in experiments and phase-field simulations (Fig. S15). To further uncover effective strategies for controlling local photostriction in bulk ferroelectrics, we explored the underlying structural driving forces for regulating ferroelectric domains.\u003c/p\u003e\n\u003cp\u003eThe composition-driven evolution of ferroelectric domains originates from changes in local spontaneous polarization, specifically, \u003cem\u003eDP\u003c/em\u003e and \u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ea). To uncover the atomic-scale driving forces for \u003cem\u003eDP\u003c/em\u003e and \u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e, we conducted a statistical correlation analysis linking these polarization parameters to key microstructural factors, including A-site cation variations (reflected by A-site cation intensity variations), oxygen octahedral tilt (\u003cem\u003eOT\u003c/em\u003e), and oxygen octahedral distortion (\u003cem\u003eOD\u003c/em\u003e). This analysis was based on atomic-scale mapping of these microstructural features, as provided in Figs. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eb and \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ec (details can be seen in Supplementary Methods 1.3 and Figs. S16 and S17). Our analysis reveals a pronounced negative correlation between \u003cem\u003eDP\u003c/em\u003e and \u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ed), indicating that larger \u003cem\u003eDP\u003c/em\u003e correspond to lower \u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e. This interdependence suggests a mutually competitive relationship between \u003cem\u003eDP\u003c/em\u003e and \u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e. As provided in Figs. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ee and \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ef, \u003cem\u003eOT\u003c/em\u003e is correlated with \u003cem\u003eDP\u003c/em\u003e, whereas \u003cem\u003eOD\u003c/em\u003e is correlated with \u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e. Given that large \u003cem\u003eOD\u003c/em\u003e characterizes domain walls, increasing \u003cem\u003eOT\u003c/em\u003e thus serves as the primary driving force for reducing domain size. In contrast, increasing \u003cem\u003eOD\u003c/em\u003e acts as the main driving force in enhancing \u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e.\u003c/p\u003e\n\u003cp\u003eTo further elucidate the driving forces of evolving \u003cem\u003eOT\u003c/em\u003e and \u003cem\u003eOD\u003c/em\u003e, we statistically analyzed variations in the relative lengths of A\u0026ndash;O and B\u0026ndash;O bonds and correlated them with \u003cem\u003eOT\u003c/em\u003e and \u003cem\u003eOD\u003c/em\u003e (Figs. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eg and \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eh). Fluctuation in B\u0026ndash;O bond lengths positively correlates with \u003cem\u003eOD\u003c/em\u003e, whereas variation in A\u0026ndash;O bond lengths correlates positively with \u003cem\u003eOT\u003c/em\u003e. These insights suggest that compositional adjustments targeting A\u0026ndash;O and B\u0026ndash;O bonds modifications could effectively tune \u003cem\u003eOD\u003c/em\u003e and \u003cem\u003eOT\u003c/em\u003e, thus balancing the competition between \u003cem\u003eDP\u003c/em\u003e and \u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e. Under near-critical conditions, this strategy can achieve large \u003cem\u003eDP\u003c/em\u003e while preserving relatively high \u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e. In size-reduced domains, each domain retains a high \u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e, promoting efficient migration of photo-induced charge carriers toward domain walls. These charge carriers shield bound charges at domain walls, reduce depolarization fields, and thus facilitate rapid and enhanced local photostriction. Correlation coefficients among these local structural factors were provided in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ei, demonstrating the statistical reliability of our identified structural driving forces for modulating the domains.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOpto-ultrasound Generation and Remote SHM via Photostriction\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe designed a remote ultrasonic SHM system enabled by the photostricton in KNN-0.02Tb, to monitor the damage status of engineering structures\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. The system employs a KNN-0.02Tb optomechanical cantilever transducer with the size of 0.25 mm \u0026times; 0.50 mm \u0026times; 3.00 mm (width \u0026times; height \u0026times; length), bonded to a 1.6 mm-thick aluminum plate (selection details in Supplementary Note 7). When illuminated by continuous light modulated at 50.3 kHz corresponding to the resonance frequency of the coupled cantilever structure, the cantilever generates mechanical vibration due to photostriction in KNN-0.02Tb, exciting an ultrasonic wave propagating through the aluminum substrate. A laser scanning vibrometer captures the vibrational profiles, enabling real-time monitoring of defects, by analyzing amplitude and phase changes in the ultrasonic waves interacted with structural defects (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea).\u003c/p\u003e\n\u003cp\u003eTo assess reproducibility of this KNN-0.02Tb optomechanical transducer, cyclic on-off illumination tests were performed on it, with each \u0026quot;on\u0026quot; state inducing 500 electrical oscillations, repeated over seven on-off cycles (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003eb). The results confirm the cantilever\u0026rsquo;s reliability as an opto-mechanical transmitter. The system exhibited efficient wave coupling, producing ultrasonic signals with consistent periodicity (18.1 mm wavelength) and minimal attenuation across the pristine aluminum plate (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ec). Damped sine wave fitting (R\u0026sup2; \u0026gt;0.95) validated stable signal propagation, while spectral analysis confirmed frequency fidelity between the input modulation signals (50.3 kHz) and detected waveforms.\u003c/p\u003e\n\u003cp\u003eThe defect detection capability was evaluated using 4 mm \u0026times; 22 mm strip defects of varying depths (0\u0026ndash;1.6 mm), positioned 45 mm from the transmitter (Fig. S18). A 5-cycle, 3-V\u003csub\u003epp\u003c/sub\u003e, 50.3 kHz sine wave was applied to modulate the illumination on the KNN-0.02Tb transmitter, generating a A0 Lamb ultrasonic wave\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e detected by the laser scanning vibrometer (see mode determination in Fig. S19). Signal attenuation exhibited a clear correlation with defect depth, while a normalized damage index (DI), derived from the amplitude comparison between pristine and defected states (see Supplementary Note 6), increased with the defect depth with consistent trend, until approaching the full plate thickness (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ed). These experimental results demonstrate the feasibility of using the non-poled KNN-Tb ceramics for realizing remote opto-ultrasonic SHM in practical applications. Given the complexity of the poling process and depoling issue during long-term monitoring operation, using the non-poled KNN-Tb offers a cost-effective approach with improved robustness in manufacturing the next-generation optomechanical devices.\u003c/p\u003e\n\u003cp\u003eIn summary, we achieved an outstanding photostriction rate of 6.41 \u0026times; 10⁻\u003csup\u003e1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in non-poled terbium-doped (K,Na)NbO₃ (KNN-Tb) ceramics, two orders of magnitude higher than typical ferroelectrics as previously reported in the literature. The exceptional photostriction performance results from enhanced coupling between the effective nanoscale photovoltaic effect and converse piezoelectric response, combined with optimized optical penetration in KNN-Tb ceramics, improving local photostriction and its constructive accumulation. Atomic-resolution analysis reveals that the heavy hetero-ions introduced at the A-site modulate metal-oxygen bond lengths, tailoring oxygen octahedral tilt (\u003cem\u003eOT\u003c/em\u003e) and distortion (\u003cem\u003eOD\u003c/em\u003e) level, and impact both the polarization angle deviation (\u003cem\u003eDP\u003c/em\u003e) and magnitude (\u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e). The competitive interplay between \u003cem\u003eDP\u003c/em\u003e and \u003cem\u003eP\u003c/em\u003e\u003csub\u003emag\u003c/sub\u003e fosters optimal ferroelectric domain configuration that facilitates the migration of photo-induced carriers to domain walls, leading to the large and rapid local photostriction. Optimized optical penetration facilitates more grain participation in light\u0026ndash;lattice interactions, promoting greater accumulation of local photostriction and enhancing the collective photostriction. Intensive ultrasonic waves have been excited by light and remote ultrasonic SHM function has been demonstrated, using an opto-ultrasonic cantilever transducer made from the KNN-Tb ceramics. Our research outcome here illustrates a versatile approach for engineering multiscale structures in bulk ferroelectrics, enabling giant photostriction rate for next-generation opto-acoustic devices innovation, and provides a unique technical solution for remote opto-ultrasound applications.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eSee details of methods part in supplementary information files.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eCompeting interests\u003c/h2\u003e\u003cp\u003eThe authors declare no conflict of interest.\u003c/p\u003e\u003ch2\u003eAuthor Contributions\u003c/h2\u003e\u003cp\u003eThe work was designed and guided by J. Y., H. W., J. W., and K. Y. Material selection, material fabrication by J. Y., H. T., C. Z. and C. L. Device design, improvement and testing by J. Y. The ultrasonic data processing and analysis were done by J. Y. X. S. conducted phase-field simulations. H. T. and J. Y. conducted the PFM characterization and analysis. H. W. and Y. Y. conducted the (S)TEM characterization and analysis. D. B. K. L. provided technical support for device fabrication and optimization. L. L. and Y. S. provided technical discussions on the acoustic wave characterization by using the laser scanning vibrometer. J. Y., H. W., F. L., K.Y. and J. W. summarized and analyzed the data, and discussed the results. All authors contributed to discussing and writing the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e\u003cp\u003eThe authors acknowledge the research grant supported by National Key R\u0026amp;D Program of China (2021YFB3201100), A*STAR-RIE2020 AME Industry Alignment Fund\u0026ndash;Pre-positioning Programme (IAF-PP) (grant no. A20F5a0043), AME Programmatic Fund (Grant No. A20G9b0135), and IAF311014R, and by the National Natural Science Foundation of China (U23A20567, 2172128, 52172128 and 52472250). The authors acknowledge the technical support and discussions from TaiHang Laboratory and Zhejiang Shunhui Optical Technology Co., Ltd.\u003c/p\u003e\u003ch2\u003eData availability\u003c/h2\u003e\u003cp\u003eThe data corresponding to this study are available from the first author and corresponding authors upon request.\u003c/p\u003e\u003ch2\u003eCode availability\u003c/h2\u003e\u003cp\u003eMATLAB scripts are available from the first author and corresponding authors upon request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eChaikin PM, Lubensky TC, Witten TA (1995) \u003cem\u003ePrinciples of condensed matter physics\u003c/em\u003e. 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IEEE Sens J 17(11):3354\u0026ndash;3361\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-7177986/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7177986/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eExtending photocarrier lifetime, accelerating photostrictive strain buildup, and engaging more light–lattice interactions are key to improving bulk ferroelectric photostriction rate (coefficient integrating strain magnitude and generation speed, typically \u0026lt; 10⁻³ s⁻¹) for reliable remote ultrasound generation. We report non-poled terbium-doped (K,Na)NbO₃ ceramics (KNN-Tb), where Tb³⁺ 4\u003cem\u003ef\u003c/em\u003e-electron trapping prolongs photocarrier lifetime, enabling efficient carrier migration to domain walls for screening depolarization field. Hierarchical nanostructures—dense nanodomains (rapid local photostriction) and subwavelength grains (more light–lattice interactions and enhanced collective strain)—yield the photostriction rate of 6.41×10⁻¹ s⁻¹, two orders above conventional bulk ferroelectrics. Non-poled KNN-Tb avoids depoling issue, enabling robust opto-ultrasonic transducers that generate intense ultrasound under low-cost laser, demonstrated remote structural health monitoring. Our bulk ferroelectric design strategy enables cost-effective, high-performance remote opto-ultrasonic sensing technologies.\u003c/p\u003e","manuscriptTitle":"Giant Photostriction Rate for Remote Opto-ultrasonic Structural Health Monitoring","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-18 04:47:19","doi":"10.21203/rs.3.rs-7177986/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"112c67f0-04d5-496b-8b42-4be8dcd477dc","owner":[],"postedDate":"August 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":53139715,"name":"Physical sciences/Materials science/Condensed-matter physics/Ferroelectrics and multiferroics"},{"id":53139716,"name":"Physical sciences/Optics and photonics/Optical materials and structures"}],"tags":[],"updatedAt":"2026-04-02T07:12:31+00:00","versionOfRecord":{"articleIdentity":"rs-7177986","link":"https://doi.org/10.1038/s41467-026-69906-y","journal":{"identity":"nature-communications","isVorOnly":false,"title":"Nature Communications"},"publishedOn":"2026-02-24 05:00:00","publishedOnDateReadable":"February 24th, 2026"},"versionCreatedAt":"2025-08-18 04:47:19","video":"","vorDoi":"10.1038/s41467-026-69906-y","vorDoiUrl":"https://doi.org/10.1038/s41467-026-69906-y","workflowStages":[]},"version":"v1","identity":"rs-7177986","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7177986","identity":"rs-7177986","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}