Ottman A. Tertuliano

Bioinspired hierarchical microstructures offer a route toward engineered fatigue resistance in additively manufactured alloys. However, it remains unclear how discrete structural constituents independently govern damage accumulation, particularly during the critical fatigue initiation regime where short cracks strongly interact with local microstructure. Here, we investigate multiscale fatigue initiation in a dual-phase, nanolamellar AlCoCrFeNi 2.1 high-entropy alloy. By comparing microscale specimens that isolate the nanolamellar structure against macroscale specimens containing the full melt-pool architecture, we identify size-dependent fatigue initiation mechanisms. We find that failure is dictated by nanolamellar interfaces at the microscale, whereas mesoscale melt pool boundaries serve to initiate fatigue at the macroscale. This mechanistic shift is accompanied by a transition from macroscale quasi-brittle failure to microscale plasticity-driven crack extension. Our results provide a physical framework for understanding how structural hierarchy governs the transition from discrete microstructural deformation to continuum fatigue fracture behavior, informing the design of damage-tolerant, additively manufactured alloys.

Cells in load-bearing tissues experience both solid deformation and interstitial fluid flow during physiological loading, but the mechanisms by which they integrate these poroelastic mechanical signals remain poorly understood. Here, we develop a porous, nanoarchitected 3D scaffold that allows simultaneous delivery and control of matrix strain and fluid shear stress. We validated the platform through cyclic loading experiments and simulations of fluid-structure interactions. In static, stress-free culture mechanical environments, osteoblast-like cells adopted shapes, cytoskeletal architectures, and focal adhesion patterns templated by the 3D scaffold geometry. Under cyclic compression, the combined influence of matrix deformation and induced fluid flow disrupted this alignment, producing disordered actin structures and reduced focal adhesion eccentricity. These changes emerged even under low-frequency loading, within the drained poroelastic regime, indicating a high sensitivity of cytoskeletal organization to fluid-solid coupling. Our findings establish a tractable and tunable platform to investigate how cells sense and respond to dynamic poroelastic mechanical environments in 3D.

Engineering connectivity at the nanoscale enables unprecedented mechanical metamaterials with exotic properties. However, nanomanufacturing 3D lattices with molecular connectivity and tunable topologies is challenging. Here, we select a supramolecular material named metal–organic framework (MOF) as the prototype, where molecules are employed as nodes and beams to construct nanosized truss lattices. An MOF named PCN-700 featuring a well-defined body-centered cubic structure is synthesized, of which the molecular connectivity, topology, and internal stress can be precisely tuned via postsynthetic installation of organic linkers with variable lengths. Herein, the topology is regulated with subnanometer resolution, affording lightweight materials with tunable elastic moduli (8.9–17.4 GPa) without apparent density changes, confirmed by atomic force microscopy indentation. The study of the compressive behaviors from nanonewton to millinewton regimes establishes a connection between the intrinsic chemical structures and the mechanical properties, where the molecular connectivity determines the lattice deformation mode. Raman spectra and ab initio calculations indicate that the PCN-700 can accommodate compressive deformation through the rotation of molecular planes within the organic ligands, contributing to the integral stiffness. The insights presented here will not only uncover MOFs’ application potentials in mechanics but also inspire chemical design and precision engineering of mechanical metamaterials at the nanoscale.

Biocompatible adhesive Resin A multi-functional polymeric resin system based on thiol-ene crosslinking provides a strong adhesive interface with dentin that composes the inside structures of teeth and is biocompatible with dental pulp cells residing in the dentinal tubules that extend from the dentin surface. More details can be found in the Research Article by Kyle H. Vining and co-workers (DOI: 10.1002/adhm.202501993).

Abstract Bone endures millions of cycles throughout its lifetime by accumulating damage at a rate slow enough to allow for cell-mediated repair, but the mechanisms that delay this fatigue failure remain poorly understood. While prior studies have focused on the fatigue response of macroscale architecture of bone, the role of it’s nanoscale structure in resisting fatigue has been experimentally inaccessible. Here, we combine in-situ fatigue loading with synchrotron X-ray tomography and radiography to directly observe crack propagation in human bone with ∼ 21 nm spatial and 100 ms temporal resolution. We find that mineralized collagen fibrils decelerate crack growth through branching along the fibril axes, while orthogonal cracks are intermittently decelerated by nanoscale interfibrillar interfaces. These mechanisms suppress damage accumulation under physiological loads by an order of magnitude. Our findings uncover a previously unobserved toughening strategy at the nanoscale, providing insight as to how the hierarchical structure of bone bridges the timescale gap between mechanical damage and biological repair.

This study develops a biocompatible multifunctional thiol-ene resin system for adhesion to dentin mineralized tissue. Adhesive resins maintain the strength and longevity of dental composite restorations through chemophysical bonding to exposed dentin surfaces after cavity preparations. Monomers of conventional adhesive systems may result in inhomogeneous polymer networks and the release of residual monomers that cause cytotoxicity. In this study, a one-step multifunctional polymeric resin system by incorporating trimethylolpropane triacrylate (TMPTA) and bis[2-(methacryloyloxy)ethyl] phosphate (BMEP) is developed to enhance both mechanical properties and adhesion to dentin. Molecular dynamics simulations identify an optimal triacylate:trithiol ratio of 2.5:1, which is consistent with rheological and mechanical tests that yield a storage modulus of ≈30 MPa with or without BMEP. Shear bond tests demonstrate that the addition of BMEP significantly improves dentin adhesion, achieving a shear bond strength of 10.8 MPa, comparable to the commercial primer Clearfil SE Bond. Nanoindentation modulus mapping characterizes the hybrid layer and mechanical gradient of the adhesive resin system. Further, the triacrylate-BMEP resin shows biocompatibility with dental pulp cells and fibroblasts in vitro. These findings suggest that the triacrylate-trithiol crosslinking and chemophysical bonding of BMEP provide enhanced bond strength and biocompatibility for dental applications.

Abstract Cells in load-bearing tissues experience both solid deformation and interstitial fluid flow during physiological loading, but the mechanisms by which they integrate these biphasic mechanical signals remain poorly understood. Here, we develop a porous, nanoarchitected 3D scaffold that allows simultaneous delivery and control of matrix strain and fluid shear stress. We validated the platform through fatigue loading experiments and simulations of fluid–structure interactions. In static culture, osteoblast-like cells adopted shapes, cytoskeletal architectures, and focal adhesion patterns templated by scaffold geometry. Under cyclic compression, the combined influence of matrix deformation and induced fluid flow disrupted this alignment, producing disordered actin structures and reduced focal adhesion eccentricity. These changes emerged even under low-frequency loading, within the drained poroelastic regime, indicating a high sensitivity of cytoskeletal organization to fluid-solid coupling. Our findings establish a tractable and tunable platform to investigate how cells sense and respond to dynamic biphasic mechanical environments in 3D. Significance Statement Cells in tissues such as bone experience mechanical inputs from both matrix deformation and interstitial fluid flow. However, existing in vitro systems often isolate one type of input or lack the ability to control both independently. We engineered a nanoarchitected 3D scaffold that delivers tunable biphasic mechanical inputs by combining structural compression and fluid flow. Without external loads, cells align their cytoskeleton and focal adhesions to the scaffold geometry. When subjected to dynamic loading, they transition to disordered morphologies and less mature focal adhesions, suggesting a transition to migratory states. These results highlight the sensitivity of cells to even subtle biphasic cues and provide a new platform to study how cells integrate multiple mechanical signals in 3D environments.

This study developed a biocompatible multifunctional thiol-ene resin system for adhesion to dentin mineralized tissue. Adhesive resins maintain the strength and longevity of dental composite restorations through chemophysical bonding to exposed dentin surfaces after cavity preparations. Dental pulp cells are exposed to residual monomers transported through dentinal tubules. Monomers of conventional adhesive systems may result in inhomogeneous polymer networks and the release of residual monomers that cause cytotoxicity. In this study, we develop a one-step multi-functional polymeric resin system by incorporating trimethylolpropane triacrylate (TMPTA) and bis[2-(methacryloyloxy)ethyl] phosphate (BMEP) to enhance both mechanical properties and adhesion to dentin. Molecular dynamics simulations identified an optimal triacylate:trithiol ratio of 2.5:1, which was consistent with rheological and mechanical tests that yielded a storage modulus of ~30 MPa with or without BMEP. Shear bond tests demonstrated that the addition of BMEP significantly improved dentin adhesion, achieving a shear bond strength of 10.8 MPa, comparable to the commercial primer Clearfil SE Bond. Nanoindentation modulus mapping characterized the hybrid layer and mechanical gradient of the adhesive resin system. Further, the triacrylate-BMEP resin showed biocompatibility with fibroblasts in vitro. These findings suggest the triacrylate-trithiol crosslinking and chemophysical bonding of BMEP provide enhanced bond strength and biocompatibility for dental applications.

Two-dimensional (2D) van der Waals materials exhibit exceptional in-plane mechanical and transport properties, yet leveraging these properties in three dimensions (3D) remains a fundamental challenge. Here, we introduce a high-throughput method for the spontaneous formation of three-dimensional auto-kirigami, self-fractured and self-folded structures that evolve during indentation of thin (<100 nm) flakes of graphite and hexagonal boron nitride. These 3D structures provide direct access to in-plane properties via out-of-plane fractured surfaces, demonstrating enhanced electrical conductance along these edges. The 3D auto-kirigami consist of 2-4 plates, or "leaflets", that form by elastic buckling facilitated by in-plane fracture. By analyzing hundreds of leaflet geometries, we demonstrate that leaflet length correlates with buckling load, enabling a real-time predictor of the leaflet morphology. These 3D auto-kirigami provide a high-yield, deformation-driven platform for 3D van der Waals structures that can leverage in-plane properties of 2D materials.

The widespread application of metal additive manufacturing (AM) is limited by the ability to control the complex interactions between the energy source and the feedstock material. Here, we develop a generalizable process to introduce nanoscale grooves to the surface of metal powders which increases the powder absorptivity by up to 70% during laser powder bed fusion. Absorptivity enhancements in copper, copper-silver, and tungsten enable energy-efficient manufacturing, with printing of pure copper at relative densities up to 92% using laser energy densities as low as 83 joules per cubic millimeter. Simulations show that the enhanced powder absorptivity results from plasmon-enabled light concentration in nanoscale grooves combined with multiple scattering events. The approach taken here demonstrates a general method to enhance the absorptivity and printability of reflective and refractory metal powders by changing the surface morphology of the feedstock without altering its composition.

Bamboo has a functionally-graded microstructure that endows it with a combination of desirable properties, such as high failure strain, high toughness, and a low density. As a result, bamboo has been widely used in load-bearing structures. In this work, we study the use of bamboo-inspired void patterns to geometrically improve the failure properties of structures made from brittle polymers. We perform finite element analysis and experiments on 3D-printed structures to quantify the effect of the shape and spatial distribution of voids on the fracture behavior. The introduction of periodic, uniformly distributed voids in notched bend specimens leads to a 15-fold increase in the fracture energy relative to solid specimens. Adding a gradient to the pattern of voids leads to a cumulative 55-fold improvement in the fracture energy. Mechanistically, the individual voids result in crack blunting, which suppresses crack initiation, while neighboring voids redistribute stresses throughout the sample to enable large deformation before failure.

The widespread application of metal additive manufacturing (AM) is limited by the ability to control the complex interactions between the energy source and the feedstock material. Here we develop a generalizable process to introduce nanoscale grooves to the surface of metal powders which increases the powder absorptivity by up to 70% during laser powder bed fusion. Absorptivity enhancements in copper, copper-silver, and tungsten enables energy efficient manufacturing, with printing of pure copper at relative densities up to 92% using laser energy densities as low as 82 J/mm^3. Simulations show the enhanced powder absorptivity results from plasmon-enabled light concentration in nanoscale grooves combined with multiple scattering events. The approach taken here demonstrates a general method to enhance the absorptivity and printability of reflective and refractory metal powders by changing the surface morphology of the feedstock without altering its composition.

Bamboo has a functionally-graded microstructure that endows it with a combination of desirable properties, such as high failure strain, high toughness, and a low density. As a result, bamboo has been widely used in load-bearing structures. In this work, we study the use of bamboo-inspired void patterns to geometrically improve the failure properties of structures made from brittle polymers. We perform finite element analysis and experiments on 3D-printed structures to quantify the effect of the shape and spatial distribution of voids on the fracture behavior. The introduction of periodic, uniformly distributed voids in notched bend specimens leads to a 15-fold increase in the work of fracture relative to solid specimens. Adding a gradient to the pattern of voids leads to a cumulative 55-fold improvement in the work of fracture. Mechanistically, the individual voids result in crack blunting, which suppresses crack initiation, while neighboring voids redistribute stresses throughout the sample to enable large deformation before failure. In addition, we conduct qualitative, low-energy impact experiments on PMMA plates with laser-cut void patterns, illustrating the broader potential for this strategy to improve damage tolerance and energy absorption in a wide range of materials systems.