Pub Date : 2025-06-03DOI: 10.1016/j.eml.2025.102366
Yun Shi , Jiali Cheng , Guangyuan Su , Meiying Zhao , Yongquan Liu , Bing Li
Defects offer a new geometric freedom in metamaterials or phononic crystals to functionally modulate waves, but remain unexplored in a low-dimensional version of artificial structures. We here introduce the concept of a defected metasurface that enables structured focusing by breaking the traditional design notion of perfect metasurfaces for single focus. We theoretically and experimentally demonstrate that the distance between focal points is smaller than the wavelength, which is a challenging task previously. Moreover, the number and the energy distribution of foci can be tailored via integrating defects with the metasurface, which can be well described based on the Babinet principle. We further realize the Talbot effect to generate periodically focusing and digital coding. This defected prototype offers a promising strategy to shape structured elastic waves for nondestructive testing, and may be extended to other fields on the design of efficient acoustic or optical tweezer arrays.
{"title":"Defected elastic metasurfaces for structured focusing with the extension of Babinet principle","authors":"Yun Shi , Jiali Cheng , Guangyuan Su , Meiying Zhao , Yongquan Liu , Bing Li","doi":"10.1016/j.eml.2025.102366","DOIUrl":"10.1016/j.eml.2025.102366","url":null,"abstract":"<div><div>Defects offer a new geometric freedom in metamaterials or phononic crystals to functionally modulate waves, but remain unexplored in a low-dimensional version of artificial structures. We here introduce the concept of a defected metasurface that enables structured focusing by breaking the traditional design notion of perfect metasurfaces for single focus. We theoretically and experimentally demonstrate that the distance between focal points is smaller than the wavelength, which is a challenging task previously. Moreover, the number and the energy distribution of foci can be tailored via integrating defects with the metasurface, which can be well described based on the Babinet principle. We further realize the Talbot effect to generate periodically focusing and digital coding. This defected prototype offers a promising strategy to shape structured elastic waves for nondestructive testing, and may be extended to other fields on the design of efficient acoustic or optical tweezer arrays.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"78 ","pages":"Article 102366"},"PeriodicalIF":4.3,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144242040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-03DOI: 10.1016/j.eml.2025.102358
R. Pramanik , M. Park , Z. Ren , M. Sitti , R.W.C.P. Verstappen , P.R. Onck
Miniaturized magnetic soft robots have shown extraordinary capabilities of contactless manipulation, complex path maneuvering, precise localization, and rapid actuation, enabling them to cater to challenging biomedical applications such as targeted drug delivery, internal wound healing, and laparoscopic surgery. However, despite their successful fabrication by several different research groups, a thorough design strategy encompassing the optimized kinematic performance of the three fundamental biomimetic swimming modes at miniaturized length scales has not been reported until now. Here, we resolve this by designing magnetic soft robotic swimmers (MSRSs) from the class of helical and undulatory low Reynolds number (Re) swimmers using a fully coupled, experimentally calibrated computational fluid dynamics model. We study (and compare) their swimming performance, and report their steady-state swimming speed for different non-dimensional numbers that capture the competition by magnetic loading, nonlinear elastic deformation, and viscous solid–fluid coupling. We investigated their stability for different initial spatial orientations to ensure robustness during real-life applications. Our results show that the helical ’finger-shaped’ swimmer is by far the fastest low Re swimmer in terms of body lengths per cycle, but that the undulatory ’carangiform-like’ swimmer proved to be the most versatile, bidirectional swimmer with maximum stability.
{"title":"Computational and experimental design of fast and versatile magnetic soft robotic low Re swimmers","authors":"R. Pramanik , M. Park , Z. Ren , M. Sitti , R.W.C.P. Verstappen , P.R. Onck","doi":"10.1016/j.eml.2025.102358","DOIUrl":"10.1016/j.eml.2025.102358","url":null,"abstract":"<div><div>Miniaturized magnetic soft robots have shown extraordinary capabilities of contactless manipulation, complex path maneuvering, precise localization, and rapid actuation, enabling them to cater to challenging biomedical applications such as targeted drug delivery, internal wound healing, and laparoscopic surgery. However, despite their successful fabrication by several different research groups, a thorough design strategy encompassing the optimized kinematic performance of the three fundamental biomimetic swimming modes at miniaturized length scales has not been reported until now. Here, we resolve this by designing magnetic soft robotic swimmers (MSRSs) from the class of helical and undulatory low Reynolds number (Re) swimmers using a fully coupled, experimentally calibrated computational fluid dynamics model. We study (and compare) their swimming performance, and report their steady-state swimming speed for different non-dimensional numbers that capture the competition by magnetic loading, nonlinear elastic deformation, and viscous solid–fluid coupling. We investigated their stability for different initial spatial orientations to ensure robustness during real-life applications. Our results show that the helical ’finger-shaped’ swimmer is by far the fastest low Re swimmer in terms of body lengths per cycle, but that the undulatory ’carangiform-like’ swimmer proved to be the most versatile, bidirectional swimmer with maximum stability.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"78 ","pages":"Article 102358"},"PeriodicalIF":4.3,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144221197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-02DOI: 10.1016/j.eml.2025.102354
Brandon K. Zimmerman , Rebecca Schulman , Thao D. Nguyen
Polymeric gels crosslinked by DNA sequences can exploit DNA strand-displacement reactions to promote swelling through dynamic polymerization. The degree of swelling and the rate of swelling must be directly tunable to achieve the promise of programmable soft matter. Though the kinetics of the strand-displacement reaction provide insertion rates up to /Molar/second as measured in bulk solution, DNA hydrogel swelling can take upwards of 30 h to complete. Computational modeling of the reaction-induced swelling of these gels with our recently-developed reactive electrochemomechanical theory (Zimmerman et al., 2024) suggests that their extraordinarily slow swelling is partly due to a scaling mismatch between the addition of charge and the addition of fluid volume, leading to a large transient increase in the fixed charge density. The significant increase in the gel’s fixed charge density, due to the binding of negatively charged DNA, sharply restricts the concentration of mobile hairpins through the phenomenon of Donnan charge exclusion, an effect commonly exploited in nanofiltration applications using polymeric membranes. The scaling problem is overcome when the mean additional swelling provided to the hydrogel by addition of a crosslink is above a critical value, thus the swelling outpaces the charge accumulation, leading the fixed charge density to drop and significantly accelerating the swelling process. This study shows that Donnan exclusion can explain the kinetics of DNA hydrogel swelling, and studies ways to modulate the reaction speed by either modifying the salt concentration or increasing or decreasing the number of base pairs in each DNA sequence.
由DNA序列交联的聚合物凝胶可以利用DNA链位移反应通过动态聚合促进膨胀。膨胀的程度和膨胀的速度必须直接可调，以实现可编程软物质的承诺。虽然链位移反应的动力学提供的插入速率高达104/摩尔/秒，但DNA水凝胶膨胀可能需要30小时以上才能完成。利用我们最近开发的反应性电化学力学理论（Zimmerman et al., 2024）对这些凝胶的反应诱导膨胀进行计算建模表明，它们异常缓慢的膨胀部分是由于添加电荷和添加流体体积之间的尺度不匹配，导致固定电荷密度瞬间大幅增加。由于带负电荷的DNA的结合，凝胶的固定电荷密度显著增加，通过Donnan电荷排除现象，极大地限制了移动发夹的浓度，这种效应通常用于使用聚合物膜的纳滤应用。当添加交联给水凝胶提供的平均额外膨胀超过临界值时，就可以克服结垢问题，因此膨胀速度超过电荷积累速度，导致固定电荷密度下降，并显著加速膨胀过程。本研究表明，Donnan不排除可以解释DNA水凝胶膨胀的动力学，并研究了通过改变盐浓度或增加或减少每个DNA序列的碱基对数量来调节反应速度的方法。
{"title":"Growth-induced Donnan exclusion influences swelling kinetics in highly charged dynamic polymerization hydrogels","authors":"Brandon K. Zimmerman , Rebecca Schulman , Thao D. Nguyen","doi":"10.1016/j.eml.2025.102354","DOIUrl":"10.1016/j.eml.2025.102354","url":null,"abstract":"<div><div>Polymeric gels crosslinked by DNA sequences can exploit DNA strand-displacement reactions to promote swelling through dynamic polymerization. The degree of swelling and the rate of swelling must be directly tunable to achieve the promise of programmable soft matter. Though the kinetics of the strand-displacement reaction provide insertion rates up to <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup></mrow></math></span>/Molar/second as measured in bulk solution, DNA hydrogel swelling can take upwards of 30 h to complete. Computational modeling of the reaction-induced swelling of these gels with our recently-developed reactive electrochemomechanical theory (Zimmerman et al., 2024) suggests that their extraordinarily slow swelling is partly due to a scaling mismatch between the addition of charge and the addition of fluid volume, leading to a large transient increase in the fixed charge density. The significant increase in the gel’s fixed charge density, due to the binding of negatively charged DNA, sharply restricts the concentration of mobile hairpins through the phenomenon of Donnan charge exclusion, an effect commonly exploited in nanofiltration applications using polymeric membranes. The scaling problem is overcome when the mean additional swelling provided to the hydrogel by addition of a crosslink is above a critical value, thus the swelling outpaces the charge accumulation, leading the fixed charge density to drop and significantly accelerating the swelling process. This study shows that Donnan exclusion can explain the kinetics of DNA hydrogel swelling, and studies ways to modulate the reaction speed by either modifying the salt concentration or increasing or decreasing the number of base pairs in each DNA sequence.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"78 ","pages":"Article 102354"},"PeriodicalIF":4.3,"publicationDate":"2025-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144221198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-01DOI: 10.1016/j.eml.2025.102303
Peidong Zhang , Tong Zhou , Kuan Zhang , Yifei Luo , Yang Li
{"title":"Corrigendum to “High-stiffness reconfigurable surfaces based on bistable element assembly and bi-compatible truss attachment’’ [Extreme Mech. Lett. 71 (September) (2024) 102187]","authors":"Peidong Zhang , Tong Zhou , Kuan Zhang , Yifei Luo , Yang Li","doi":"10.1016/j.eml.2025.102303","DOIUrl":"10.1016/j.eml.2025.102303","url":null,"abstract":"","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102303"},"PeriodicalIF":4.3,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144196185","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-30DOI: 10.1016/j.eml.2025.102367
Jingping Wu, Zhengjin Wang, Xiao Liu, Yong Zheng, Yang Gao, Jian Hu
Hydrogels with high water content and toughness are essential to various applications in smart materials and biomimetic systems. However, there exists a conflict between water content and toughness. To enhance toughness, high polymer chain density or water-free reinforcements are usually introduced into hydrogel matrices, which inevitably lead to a reduction in water content. In this study, we present a facile method for preparing water-abundant and tough hydrogels through ion transfer printing. By utilizing sodium alginate/polyacrylamide (Alg/PAAm) hydrogels as a flexible matrix and Fe3+ ions as stiffening agents, we selectively introduce Fe3+ ions into predefined regions of the hydrogel matrix, resulting in well-structured composite hydrogels comprising soft Alg/PAAm matrix and hard Fe3+-crosslinked Alg/PAAm (Fe-Alg/PAAm) fibers. As both the matrix and fibers are stretchable and water-abundant, the composites exhibit impressive stretchability (ε∼1000 %) and water content (p∼95 %). Notably, the alternating arrangement of the soft and hard fiber/matrix architecture effectively prevents crack propagation during loading by inducing stress deconcentration at the crack tip, thereby leading to exceptional toughness (Γ∼22000 J/m2). This simple method introduces a universal design strategy for constructing stretchable, water-abundant, and tough hydrogels, considering that ionic crosslinking with multi-valent cation crosslinkers is widely used in hydrogels. Beyond the Fe3+ and Alg/PAAm hydrogel system discussed here, this concept can be extended to various combinations of multi-valent ions and hydrogel networks containing opposite charges.
{"title":"Water-abundant and tough structured composite hydrogels via ion transfer printing","authors":"Jingping Wu, Zhengjin Wang, Xiao Liu, Yong Zheng, Yang Gao, Jian Hu","doi":"10.1016/j.eml.2025.102367","DOIUrl":"10.1016/j.eml.2025.102367","url":null,"abstract":"<div><div>Hydrogels with high water content and toughness are essential to various applications in smart materials and biomimetic systems. However, there exists a conflict between water content and toughness. To enhance toughness, high polymer chain density or water-free reinforcements are usually introduced into hydrogel matrices, which inevitably lead to a reduction in water content. In this study, we present a facile method for preparing water-abundant and tough hydrogels through ion transfer printing. By utilizing sodium alginate/polyacrylamide (Alg/PAAm) hydrogels as a flexible matrix and Fe<sup>3+</sup> ions as stiffening agents, we selectively introduce Fe<sup>3+</sup> ions into predefined regions of the hydrogel matrix, resulting in well-structured composite hydrogels comprising soft Alg/PAAm matrix and hard Fe<sup>3+</sup>-crosslinked Alg/PAAm (Fe-Alg/PAAm) fibers. As both the matrix and fibers are stretchable and water-abundant, the composites exhibit impressive stretchability (<em>ε</em>∼1000 %) and water content (<em>p</em>∼95 %). Notably, the alternating arrangement of the soft and hard fiber/matrix architecture effectively prevents crack propagation during loading by inducing stress deconcentration at the crack tip, thereby leading to exceptional toughness (<em>Γ</em>∼22000 J/m<sup>2</sup>). This simple method introduces a universal design strategy for constructing stretchable, water-abundant, and tough hydrogels, considering that ionic crosslinking with multi-valent cation crosslinkers is widely used in hydrogels. Beyond the Fe<sup>3+</sup> and Alg/PAAm hydrogel system discussed here, this concept can be extended to various combinations of multi-valent ions and hydrogel networks containing opposite charges.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"78 ","pages":"Article 102367"},"PeriodicalIF":4.3,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144212926","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-29DOI: 10.1016/j.eml.2025.102355
Shaohua Yang , Yue Liu , Yukun Su , Han Gao , Kaiqiang Sun , Qin Xu , Qiuting Zhang , Ye Xu
Micro-indentation has been used in measuring mechanical properties of soft materials. However, the complex contact mechanics of soft interfaces pose challenges in the accurate characterization of mechanical parameters from conventional measurement methods. In this work, we present an in situ imaging setup capable of measuring three-dimensional (3D) microscale deformation of soft elastic thin films subjected to a microindenter. Combining fluorescent confocal imaging and particle tracking techniques, microscale surface displacement profiles and stress–strain distributions are accurately quantified. Using this technique, we directly compare microscopic deformations in thin soft films with a thickness range, demonstrating the transition from “sink-in” to “pile-up” as the thickness of the film decreases. We also reveal an intricate difference in displacement fields for different lubrication conditions between the microindenter and soft thin film. These results demonstrate the capacity of our experimental setup as a powerful tool in understanding the unique micro-mechanical behaviors of various soft materials.
{"title":"Three-dimensional imaging and measurement of the microscale deformation in soft thin films under micro-indentation","authors":"Shaohua Yang , Yue Liu , Yukun Su , Han Gao , Kaiqiang Sun , Qin Xu , Qiuting Zhang , Ye Xu","doi":"10.1016/j.eml.2025.102355","DOIUrl":"10.1016/j.eml.2025.102355","url":null,"abstract":"<div><div>Micro-indentation has been used in measuring mechanical properties of soft materials. However, the complex contact mechanics of soft interfaces pose challenges in the accurate characterization of mechanical parameters from conventional measurement methods. In this work, we present an <em>in situ</em> imaging setup capable of measuring three-dimensional (3D) microscale deformation of soft elastic thin films subjected to a microindenter. Combining fluorescent confocal imaging and particle tracking techniques, microscale surface displacement profiles and stress–strain distributions are accurately quantified. Using this technique, we directly compare microscopic deformations in thin soft films with a thickness range, demonstrating the transition from “sink-in” to “pile-up” as the thickness of the film decreases. We also reveal an intricate difference in displacement fields for different lubrication conditions between the microindenter and soft thin film. These results demonstrate the capacity of our experimental setup as a powerful tool in understanding the unique micro-mechanical behaviors of various soft materials.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"78 ","pages":"Article 102355"},"PeriodicalIF":4.3,"publicationDate":"2025-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144231274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High-voltage and high-power electronic components intended for deep-sea applications encounter various challenges, including high hydrostatic pressure, temperature fluctuations, and probable seawater ingress. Consequently, encapsulation of deep-sea electronics that provides both efficient electrical insulation and pressure tolerance is crucial. This study investigates the influence of high hydrostatic pressure up to tens of MPa on the electrical breakdown of the flexible-rigid encapsulation interface, using polydimethylsiloxane and FR-4 glass epoxy as experimental materials. The experimental results show that the interface breakdown strength increases with hydrostatic pressure, in which a rapid increase is observed at 0.1 MPa to 0.75 MPa, followed by a slower rise at 0.75 MPa to 30.0 MPa. To explain this phenomenon, the cavity discharge inception field and the enhanced local electric field at contact spots under hydrostatic pressure were calculated based on interfacial contact theory. At relatively lower pressures, cavity discharge predominates in driving the interface breakdown, and the rapid growth of cavity discharge inception field leads to the sharp increase in breakdown strength with hydrostatic pressure. Whereas at higher pressures, the insulation properties of contact spots become the dominant factor. Post-breakdown analyses, including optical microscopy and micro-CT imaging, reveal that high hydrostatic pressure suppresses damage propagation, such as material carbonization, electrode defects, and gas formation. These results indicate that hydrostatic pressure helps suppress the electrical breakdown of the flexible-rigid interface. This study provides insights into the electrical breakdown behavior of flexible-rigid interfaces under high hydrostatic pressure, offering implications for the encapsulation design and optimization of deep-sea electronic components.
{"title":"Hydrostatic pressure suppresses the electrical breakdown of flexible-rigid interfaces under deep-sea","authors":"Dingnan Rao , Fanghao Zhou , Zheng Chen , Tiefeng Li","doi":"10.1016/j.eml.2025.102353","DOIUrl":"10.1016/j.eml.2025.102353","url":null,"abstract":"<div><div>High-voltage and high-power electronic components intended for deep-sea applications encounter various challenges, including high hydrostatic pressure, temperature fluctuations, and probable seawater ingress. Consequently, encapsulation of deep-sea electronics that provides both efficient electrical insulation and pressure tolerance is crucial. This study investigates the influence of high hydrostatic pressure up to tens of MPa on the electrical breakdown of the flexible-rigid encapsulation interface, using polydimethylsiloxane and FR-4 glass epoxy as experimental materials. The experimental results show that the interface breakdown strength increases with hydrostatic pressure, in which a rapid increase is observed at 0.1<!--> <!-->MPa to 0.75<!--> <!-->MPa, followed by a slower rise at 0.75<!--> <!-->MPa to 30.0<!--> <!-->MPa. To explain this phenomenon, the cavity discharge inception field and the enhanced local electric field at contact spots under hydrostatic pressure were calculated based on interfacial contact theory. At relatively lower pressures, cavity discharge predominates in driving the interface breakdown, and the rapid growth of cavity discharge inception field leads to the sharp increase in breakdown strength with hydrostatic pressure. Whereas at higher pressures, the insulation properties of contact spots become the dominant factor. Post-breakdown analyses, including optical microscopy and micro-CT imaging, reveal that high hydrostatic pressure suppresses damage propagation, such as material carbonization, electrode defects, and gas formation. These results indicate that hydrostatic pressure helps suppress the electrical breakdown of the flexible-rigid interface. This study provides insights into the electrical breakdown behavior of flexible-rigid interfaces under high hydrostatic pressure, offering implications for the encapsulation design and optimization of deep-sea electronic components.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"78 ","pages":"Article 102353"},"PeriodicalIF":4.3,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144185435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-26DOI: 10.1016/j.eml.2025.102361
HaoWen Wan , YuanZhen Hou , JiaHao Li , RongZhuang Song , YinBo Zhu , HengAn Wu
Considering the humidity-sensitivity of nanocellulose, decoding the micromechanical mechanisms hidden in hydration interface is essential for tailoring the macroscopic properties. However, exiting mechanics frameworks based on molecular modeling remain challenging to predict the hydration interface-mediated mechanical behaviors of nanocellulose at the mesoscale, hindering the correlation from micro-interface to macro-mechanics. Herein, we developed a coarse-grained (CG) model integrating non-covalent interactions and fiber-level hierarchical stacking, which unveils the anomalous mechanical enhancement of nanocellulose with hydration interfaces. The CG model, validated by all-atom (AA) simulations, accurately captured the modulus and strength scale law with overlap length, until the fiber fracture-dominated saturated state. Our results revealed how hydration extent effects the interfacial mechanics, showing that moderate hydration can enhance both toughness and strength by plasticizing hydrogen-bonding networks, while excessive hydration weakening the shear strength. Beyond the limit that AA simulations can predict, an optimal overlap regime (∼120–180 nm) was identified, where hydration-mediated interfaces can enhance the strength and toughness simultaneously. This study established a cross-scale theoretical modeling framework bridging the microscale hydration interface and macroscale mechanical regulation of nanocellulose materials, which can provide the bottom-up rational guidance for designing strong and tough nanocomposites with weak non-covalent interfaces.
{"title":"A coarse-grained model for nanocellulose with hydration interfaces revealing the anomalous mechanical enhancement","authors":"HaoWen Wan , YuanZhen Hou , JiaHao Li , RongZhuang Song , YinBo Zhu , HengAn Wu","doi":"10.1016/j.eml.2025.102361","DOIUrl":"10.1016/j.eml.2025.102361","url":null,"abstract":"<div><div>Considering the humidity-sensitivity of nanocellulose, decoding the micromechanical mechanisms hidden in hydration interface is essential for tailoring the macroscopic properties. However, exiting mechanics frameworks based on molecular modeling remain challenging to predict the hydration interface-mediated mechanical behaviors of nanocellulose at the mesoscale, hindering the correlation from micro-interface to macro-mechanics. Herein, we developed a coarse-grained (CG) model integrating non-covalent interactions and fiber-level hierarchical stacking, which unveils the anomalous mechanical enhancement of nanocellulose with hydration interfaces. The CG model, validated by all-atom (AA) simulations, accurately captured the modulus and strength scale law with overlap length, until the fiber fracture-dominated saturated state. Our results revealed how hydration extent effects the interfacial mechanics, showing that moderate hydration can enhance both toughness and strength by plasticizing hydrogen-bonding networks, while excessive hydration weakening the shear strength. Beyond the limit that AA simulations can predict, an optimal overlap regime (∼120–180 nm) was identified, where hydration-mediated interfaces can enhance the strength and toughness simultaneously. This study established a cross-scale theoretical modeling framework bridging the microscale hydration interface and macroscale mechanical regulation of nanocellulose materials, which can provide the bottom-up rational guidance for designing strong and tough nanocomposites with weak non-covalent interfaces.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"78 ","pages":"Article 102361"},"PeriodicalIF":4.3,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144167210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-26DOI: 10.1016/j.eml.2025.102362
Wenjing Lu , Chong Wang , Zidi Zhou , Shuai Xu , Zishun Liu
The intrinsic fracture energy of polymer networks describes the minimum energy required for crack propagation, excluding any inelastic dissipation within the bulk. Recent studies have demonstrated that the intrinsic fracture energy arises from two distinct contributions. The first contribution is the energy dissipated by the rupture of polymer chains along the crack path, where these chains constitute the failure zone. The second contribution is the elastic energy released from the relaxation of polymer chains adjacent to the broken chains, where these chains constitute the elastic release zone. While existing models could predict the intrinsic fracture energy of polymer networks successfully, a quantification of the two intrinsic fracture energy contributions remains elusive. Here, utilizing polyacrylamide hydrogel, we conduct a series of pure shear tests to measure the fracture energy. The size of real elastic release zone is precisely controlled in this study by varying the heights of pure shear samples. Then, for the first time, and of the polyacrylamide hydrogel are quantitatively identified based on the relationship between the apparent fracture energy and the height of sample. Moreover, our development of a modified loop-opening model represents a significant advancement in the field. This model accounts for polymer network imperfections and incorporates parameters with clear physical meanings, aligning remarkably well with our experimental findings. Based on our model, we propose a novel method for determining the size of failure zone. Furthermore, our findings offer insights into the discrepancies observed in fracture energy measurements obtained through various testing methods. This study enhances the understanding of intrinsic fracture mechanisms within polymer networks and lays the groundwork for the design of tougher polymer materials.
{"title":"Quantify the failure zone and elastic release zone: A new insight into intrinsic fracture of polymer networks","authors":"Wenjing Lu , Chong Wang , Zidi Zhou , Shuai Xu , Zishun Liu","doi":"10.1016/j.eml.2025.102362","DOIUrl":"10.1016/j.eml.2025.102362","url":null,"abstract":"<div><div>The intrinsic fracture energy of polymer networks describes the minimum energy required for crack propagation, excluding any inelastic dissipation within the bulk. Recent studies have demonstrated that the intrinsic fracture energy arises from two distinct contributions. The first contribution <span><math><msub><mrow><mi>Γ</mi></mrow><mrow><mi>f</mi></mrow></msub></math></span> is the energy dissipated by the rupture of polymer chains along the crack path, where these chains constitute the failure zone. The second contribution <span><math><msub><mrow><mi>Γ</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> is the elastic energy released from the relaxation of polymer chains adjacent to the broken chains, where these chains constitute the elastic release zone. While existing models could predict the intrinsic fracture energy of polymer networks successfully, a quantification of the two intrinsic fracture energy contributions remains elusive. Here, utilizing polyacrylamide hydrogel, we conduct a series of pure shear tests to measure the fracture energy. The size of real elastic release zone is precisely controlled in this study by varying the heights of pure shear samples. Then, for the first time, <span><math><msub><mrow><mi>Γ</mi></mrow><mrow><mi>f</mi></mrow></msub></math></span> and <span><math><msub><mrow><mi>Γ</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> of the polyacrylamide hydrogel are quantitatively identified based on the relationship between the apparent fracture energy and the height of sample. Moreover, our development of a modified loop-opening model represents a significant advancement in the field. This model accounts for polymer network imperfections and incorporates parameters with clear physical meanings, aligning remarkably well with our experimental findings. Based on our model, we propose a novel method for determining the size of failure zone. Furthermore, our findings offer insights into the discrepancies observed in fracture energy measurements obtained through various testing methods. This study enhances the understanding of intrinsic fracture mechanisms within polymer networks and lays the groundwork for the design of tougher polymer materials.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"78 ","pages":"Article 102362"},"PeriodicalIF":4.3,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144195751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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