Julia R. Greer

Julia R Greer; Analytical framework for understanding twisted 2D materials, National Science Review, , nwag339, https://doi.org/10.1093/nsr/nwag339

diffusion as the dominant factors governing active material utilization. This work introduces a versatile manufacturing platform for 3D battery components and provides insights into structure optimization for high-performance rechargeable batteries.

3D printing methods for small-scale metals enable a unique 10–100 nm dimensional niche where functional feature sizes, critical microstructural detail and atomic-level defects converge, challenging conventional hierarchical relationships and carrying significant nanomechanical implications. We introduce a metal nano-printing system combining two-photon lithography, hydrogel infusion-based additive manufacturing and in situ mechanical experiments on 3D nano-architected Ni, achieving ~100 nm critical dimensions, ~10 nm surface roughness, and a broad range of geometries (periodic vs. non-periodic; beam-based vs. shell-based) with superior specific strengths of ~100 MPa·g − 1·cm3 enabled by an unambiguous smaller is stronger size effect. Experiments identify concentrated-porosity regions as primary deformation-initiation sources and quantify their distribution as input for physics-informed, multiscale finite-element simulations that accurately predict size-dependent mechanical properties governed by nanoporosity-driven deformation. This work integrates experimental and computational approaches for the fabrication, characterization, and evaluation of nano- and micro-architected metals for nanotechnology and nanoscale manufacturing systems. A two-photon-lithography hydrogel-infusion process prints 3D nickel nano-architectures with ~100-nm features and high specific strength, indicating that localized nanoporosity hotspots govern deformation and size-dependent strength.

Abstract Advancements in additive manufacturing (AM) enable the precise engineering of micro‐architected electrodes with enhanced electrochemical and mechanical properties. Existing AM approaches for fabricating lithium‐ion battery cathodes rely on extrusion‐based direct ink‐writing, which is usually limited to 150–200 µm resolution, or vat photopolymerization (VP) 3D printing with metal salt solution, which is limited in material choices due to the complicated photoresin design and printing parameter optimization. A gel infusion AM technique is introduced to fabricate micro‐architected cathodes, using lithium cobalt oxide (LCO) as a model prototype, which utilizes VP 3D printing with a “blank” photoresin to circumvent these limitations. The synthesized micro‐architected LCO electrodes are free‐standing and binder‐free, with beam diameters below 50 µm and tunable microstructure and mechanical resilience. The nanoindentation modulus of differently oriented LCO grains varies between 148.4 and 286.6 GPa, with no grain boundary weakening. This electrode gives a reversible capacity of 122–142 mAh g −1 (11.3–13.2 mAh cm −2 ) up to a current density of 28 mA g −1 (2.6 mA cm −2 ). This method is adaptable for a broad range of cathode materials, which opens a promising pathway to fabricate micro‐architected electrodes with fully controllable form factors, versatile material choices, and micro‐sized resolution for future energy storage solutions.

Abstract In an oil well, high hydrogen content within the surrounding rocks is one indicator of the presence of hydrocarbons. Nuclear well-logging entails the deployment of a detector tool and neutron source downhole to characterise the strata properties as a function of depth. After neutron bombardment, the resulting distribution of radiation is sensitive to the hydrogen content. Current detectors favour use of radioisotopes, such as Am-Be or Cf-252 sources. Potential improvements in both safety and data collection capabilities are possible using Deuterium-Tritium Pulsed Neutron Generators (D-T PNGs) as an alternative neutron source when coupled with fast timing and position sensitive detectors. We propose a low-cost, modular detector system, that can measure the flux of thermal neutrons and gammas at various distances from a pulsed fast neutron source. The detector modules consist of in-house manufactured plastic scintillator coupled to BN:ZnS(Ag) thermal neutron converter foils. These mixed-field detectors show good figure of merit for neutron-gamma discrimination at low-cost, allowing us to construct positional and temporal distributions of detected neutrons and gammas. Based upon early simulations, these distributions are sensitive to the hydrogen content.

Abstract Hydrogel infusion‐based additive manufacturing (HIAM) is a chemically versatile solid‐state processing pathway that allows 3D structuring of ceramics and alloys with micro‐scale precision. Using thermal treatments of 3D‐printed metal ion‐infused gels, this process generates intricate microstructures throughout their complex phase evolution. Through investigation of the HIAM‐produced Cu x Ni 1‐x alloy system, substantial grain growth after reduction is shown to drive the formation of numerous annealing twins and entrap unreduced oxide nano‐inclusions, resulting in hierarchical composite microstructures. These features appear to elevate the average nanoindentation hardnesses by up to four times that of bulk annealed Cu x Ni 1‐x . Uniaxial compression of micropillars milled from individual grains reveals composition dependence on the scaling of the “smaller is stronger” size effect. This compositional dependence of deformation mechanisms arises from changes in reduction kinetics which influence the density of inclusions and voids developed by the HIAM process. This work highlights the rich microstructural landscape accessible to HIAM‐produced alloys and provides a useful pathway for the characterization and tuning of superior mechanical performance in additively manufactured alloys.

This report describes recent advances in the design and fabrication of nanostructured metallic pillars with hierarchical microstructures using a novel nanoscale additive manufacturing approach. Through a hydrogel-infusion-based two-photon lithography (TPL) method, we successfully fabricated 3D nickel nanopillars exhibiting both nanocrystalline and nanoporous features. The resulting “bamboo-like” internal architecture comprises 30–50 nm grains and voids with similarly scaled pores. These geometrically tunable pillars, with diameters ranging from ~130 to 550 nm, serve as an ideal platform for probing deformation mechanisms in structurally heterogeneous metals at the nanoscale.

The complex morphological evolution of lithium metal at the solid-state electrolyte interface limits performance of solid-state batteries, leading to inhomogeneous reactions and contact loss. Inspired by biological morphogenesis, we developed an interfacial self-regulation concept in which a deformable secondary phase dynamically aggregates at the interface in response to local electro-chemo-mechanical stimuli, enhancing contact. The stripping of a lithium electrode that contains 5 to 20 mole % electrochemically inactive sodium domains causes spontaneous sodium accumulation across the interface, with the sodium deforming to attain intimate electrical contact without blocking lithium transport. This process, characterized with operando x-ray tomography and electron microscopy, mitigates voiding and improves cycling at low stack pressures. The counterintuitive strategy of adding electrochemically inactive alkali metal to improve performance demonstrates the utility of interfacial self-regulation for solid-state batteries.

Structural heterogeneity in solid-state batteries can impact the material utilization and fracture mechanisms. Crystallographically oriented LiCoO 2 film cathodes serve as a model electrode system for exploring how void distribution contributes to stress relief and buildup during cycling. Real- and reciprocal-space operando and ex situ synchrotron-based experiments are utilized to understand structural changes across multiple length scales that contribute to stress generation and fracture. Nanotomography uncovers a depth-dependent porosity variation in the pristine electrode and highlights the preferential fracture in regions of lower porosity during delithiation. Energy-dispersive X-ray diffraction and three-dimensional (3D) X-ray absorption near-edge spectroscopy (XANES) reveal the underutilization of cathode material in these regions. 3D XANES also confirms preferential delithiation near the subgrain boundaries. Chemo-mechanical modeling coupled with site-specific mechanical characterization demonstrates how stress accumulation in dense regions of the electrode leads to fracture and underutilization of active material. Our findings reveal the importance of material design to alleviate stress in small-volume changing cathodes.

The complex and uncontrolled morphological evolution of lithium metal at the interface with solid-state electrolytes limits performance of solid-state batteries, leading to inhomogeneous reactions and contact loss. Inspired by biological morphogenesis, we introduce a new interfacial self-regulation concept in which a deformable secondary phase dynamically aggregates at the interface in response to local electro-chemo-mechanical stimuli, serving to enhance contact. Stripping of a lithium electrode containing 5-20% redox-inactive sodium domains causes spontaneous sodium accumulation across the interface, with the sodium undergoing local plastic deformation as lithium is removed to attain intimate electrical contact without blocking transport channels. This process, characterized with operando X-ray tomography and electron microscopy, mitigates void formation and substantially improves battery cycling performance at the low stack pressures needed for practical applications. The counterintuitive strategy of adding inactive alkali metal to improve performance demonstrates that interfacial self-regulation is a promising pathway to efficient solid-state batteries.

Micro- and nanorobots excel in navigating the intricate and often inaccessible areas of the human body, offering immense potential for applications such as disease diagnosis, precision drug delivery, detoxification, and minimally invasive surgery. Despite their promise, practical deployment faces hurdles, including achieving stable propulsion in complex in vivo biological environments, real-time imaging and localization through deep tissue, and precise remote control for targeted therapy and ensuring high therapeutic efficacy. To overcome these obstacles, we introduce a hydrogel-based, imaging-guided, bioresorbable acoustic microrobot (BAM) designed to navigate the human body with high stability. Constructed using two-photon polymerization, a BAM comprises magnetic nanoparticles and therapeutic agents integrated into its hydrogel matrix for precision control and drug delivery. The microrobot features an optimized surface chemistry with a hydrophobic inner layer to substantially enhance microbubble retention in biofluids with multiday functionality and a hydrophilic outer layer to minimize aggregation and promote timely degradation. The dual-opening bubble-trapping cavity design enables a BAM to maintain consistent and efficient acoustic propulsion across a range of biological fluids. Under focused ultrasound stimulation, the entrapped microbubbles oscillate and enhance the contrast for real-time ultrasound imaging, facilitating precise tracking and control of BAM movement through wireless magnetic navigation. Moreover, the hydrolysis-driven biodegradability of BAMs ensures its safe dissolution after treatment, posing no risk of long-term residual harm. Thorough in vitro and in vivo experimental evidence demonstrates the promising capabilities of BAMs in biomedical applications. This approach shows promise for advancing minimally invasive medical interventions and targeted therapeutic delivery.

In the Acknowledgements section, the following sentence, ‘The authors gratefully acknowledge the financial support from the Center for Autonomous Systems and Technologies (CAST) at Caltech, the Institute for Collaborative Biotechnologies from the Army Research Office (ARO), and the Schwartz/Reisman Collaborative Science Program from the Schwartz/Reisman Foundation’ should have read, ‘The authors gratefully acknowledge the financial support from the Center for Autonomous Systems and Technologies (CAST) at Caltech and the Schwartz/Reisman Collaborative Science Program from the Schwartz/Reisman Foundation. Research was also sponsored, in part, by the U.S. Army Research Office and accomplished under contract W911NF-19-D-0001 for the Institute for Collaborative Biotechnologies’. The original article has been corrected.

Metallo-polyelectrolytes are versatile materials for applications like filtration, biomedical devices, and sensors, due to their metal-organic synergy. Their dynamic and reversible electrostatic interactions offer high ionic conductivity, self-healing, and tunable mechanical properties. However, the knowledge gap between molecular-level dynamic bonds and continuum-level material properties persists, largely due to limited fabrication methods and a lack of theoretical design frameworks. To address this critical gap, we present a framework, combining theoretical and experimental insights, highlighting the interplay of molecular parameters in governing material properties. Using stereolithography-based additive manufacturing, we produce durable metallo-polyelectrolytes gels with tunable mechanical properties based on metal ion valency and polymer charge sparsity. Our approach unveils mechanistic insights into how these interactions propagate to macroscale properties, where higher valency ions yield stiffer, tougher materials, and lower charge sparsity alters material phase behavior. This work enhances understanding of metallo-polyelectrolytes behavior, providing a foundation for designing advanced functional materials.

Mechanical degradation of cathode active material, such as cracks result from volume changes and phase transitions, is one of the main causes of capacity fading in lithium-ion batteries. Understanding the active material’s deformation behavior during cycling and the impact of electrochemical charging on mechanical properties is crucial for understanding the mechanical degradation mechanism and extending battery lifetime. Herein, we investigate the mechanical properties of an electroplated LiCoO 2 (LCO) cathode with crystallographic texture as a function of state of charge/discharge. Nanoindentation mapping is used to detect the differences in mechanical behavior between grain boundary and grain interior region. To determine the charged LCO crystals’ mechanical properties and avoid the effects from grain boundaries and air-exposure, in-situ nanoindentation experiments are conducted in a custom mechanical testing system within a scanning electron microscope. Considering the anisotropy of LCO, electron backscatter diffraction analysis is utilized to clarify the crystallographic orientation of the electrodeposited LCO cathode. Our result shows a decreasing tendency in elastic modulus and hardness with state of charge, which can be attributed to the expansion of LCO layered structure. The recovery of mechanical properties after discharge indicates that the changes in measured mechanical properties mainly come from Li deintercalation and intercalation rather than intergranular fracture during cycling. By releasing the relationship between mechanical properties and degree of delithiation, our study provides an insight into modeling studies of electro-chemo-mechanics for electrode materials. Figure 1

Structural heterogeneity within solid-state electrodes can have a significant impact on material utilization and reaction rates. This reaction heterogeneity is greater in solid state systems in comparison to conventional liquid electrolytes because it requires exquisite solid-solid contact between the active energy storage materials and the solid ion conducting phase (e.g. solid electrolyte) [1]. Electrode reaction behaviors encompass electrochemical lithiation and delithiation dynamics and chemo-mechanical processes such as volume change and fracture [2]. Understanding the connection between structural heterogeneity and reaction behavior is crucial for understanding degradation mechanisms and optimizing solid state battery architectures. Herein, we examine the implications of reaction heterogeneity in an additive-free, crystallographically textured electroplated lithium cobalt oxide (LCO) cathode [3]. The electroplated dense cathode alleviates the need for any solid electrolyte material in the cathode. A diverse set of synchrotron-based operando and ex situ experiments are combined with modeling to uncover the relationship between structural heterogeneity and reaction behavior. Operando energy dispersive X-ray diffraction and ex situ 3D XANES are used to identify reaction heterogeneity and X-ray nanotomography is used to probe nano-scale structural heterogeneity. Nanoindentation is utilized to determine the mechanical properties of LCO. To validate the results, we combine these experimental results with transport and mechanics modeling. Through this comprehensive characterization approach, we confirm that the reaction behavior of cathode in our model is mainly determined by the morphological heterogeneity rather than the Li diffusion within the electrode. Structural heterogeneity causes localized high stress and leads to fracture, which in turn limit the full utilization of the cathode. Reference [1] Jung, S.H., Kim, U.H., Kim, J.H., Jun, S., Yoon, C.S., Jung, Y.S. and Sun, Y.K., 2020. Ni‐rich layered cathode materials with electrochemo‐mechanically compliant microstructures for all‐solid‐state Li batteries. Advanced Energy Materials, 10(6), p.1903360. [2] Liu, X., Zheng, B., Zhao, J., Zhao, W., Liang, Z., Su, Y., Xie, C., Zhou, K., Xiang, Y., Zhu, J. and Wang, H., 2021. Electrochemo‐mechanical effects on structural integrity of Ni‐rich cathodes with different microstructures in all solid‐state batteries. Advanced Energy Materials, 11(8), p.2003583. [3] Zahiri, B., Patra, A., Kiggins, C., Yong, A.X.B., Ertekin, E., Cook, J.B. and Braun, P.V., 2021. Revealing the role of the cathode–electrolyte interface on solid-state batteries. Nature Materials, 20(10), pp.1392-1400. Figure 1

Material Properties of Two-Photon Polymers With adaptive resolution two-photon polymerization (2PP) the fabrication of macroscopic material test specimens becomes possible. By combining conventional or even standardized testing methods and micromaterial testing, a comprehensive characterization of the mechanical, thermomechanical and fracture properties of materials processed with 2PP is possible. This study shows that 2PP delivers highly crosslinked polymers immediately after 3D printing without the need for post-curing. More details can be found in article number 2308497 by Thomas Koch, Aleksandr Ovsianikov, Franziska Chalupa-Gantner, Markus Lunzer, and co-workers.

Structural heterogeneity in solid-state batteries can impact material utilization and fracture mechanisms. Dense crystallographically oriented lithium cobalt oxide cathodes serve as a model electrode system for exploring how density variability contributes to stress relief and build up during cycling. Real- and reciprocal-space operando and ex-situ synchrotron based experiments are utilized to understand structural changes across multiple length scales contribute to stress generation and fracture. Nanotomography uncovers a depth-dependent porosity variation in the pristine electrode and highlights preferential fracture in regions of lower porosity during delithiation. Energy-dispersive X-ray diffraction and 3D X-ray absorption near-edge spectroscopy (XANES) reveal the underutilization of cathode material in these regions. 3D XANES also confirms preferential delithiation near the subgrain boundaries. Chemo-mechanical modeling coupled with site-specific mechanical characterization demonstrate how stress accumulation in dense regions of the electrode leads to fracture and underutilization of active material. Our findings reveal the importance of materials design to alleviate stress in small-volume changing cathodes.

Natural porous materials have exceptional properties-for example, light weight, mechanical resilience, and multi-functionality. Efforts to imitate their properties in engineered structures have limited success. This, in part, is caused by the complexity of multi-phase materials composites and by the lack of quantified understanding of each component's role in overall hierarchy. This challenge is twofold: 1) computational. because non-periodicity and defects render constructing design guidelines between geometries and mechanical properties complex and expensive and 2) experimental. because the fabrication and characterization of complex, often hierarchical and non-periodic 3D architectures is non-trivial.

Two-photon polymerization (2PP) is becoming increasingly established as additive manufacturing technology for microfabrication due to its high-resolution and the feasibility of generating complex parts. Until now, the high resolution of 2PP is also its bottleneck, as it limited throughput and therefore restricted the application to the production of microparts. Thus, mechanical properties of 2PP materials can only be characterized using nonstandardized specialized microtesting methods. Due to recent advances in 2PP technology, it is now possible to produce parts in the size of several millimeters to even centimeters, finally permitting the fabrication of macrosized testing specimens. Besides suitable hardware systems, 2PP materials exhibiting favorable mechanical properties that allow printing of up-scaled parts are strongly demanded. In this work, the up-scalability of three different photopolymers is investigated using a high-throughput 2PP system and low numerical aperture optics. Testing specimens in the cm-range are produced and tested with common or even standardized material testing methods available in conventionally equipped polymer testing labs. Examples of the characterization of mechanical, thermo-mechanical, and fracture properties of 2PP processed materials are shown. Additionally, aspects such as postprocessing and aging are investigated. This lays a foundation for future expansion of the 2PP technology to broader industrial application.

Most hexagonal boron nitride (hBN) single-photon emitters (SPEs) studied to date suffer from variable emission energy and unpredictable polarization, two crucial obstacles to their application in quantum technologies. Here, we report an SPE in hBN with an energy of 2.2444 ± 0.0013 eV created via carbon implantation that exhibits a small inhomogeneity of the emission energy. Polarization-resolved measurements reveal aligned absorption and emission dipole orientations with a 3-fold distribution, which follows the crystal symmetry. Photoluminescence excitation (PLE) spectroscopy results show the predictability of polarization is associated with a reproducible PLE band, in contrast with the non-reproducible bands found in previous hBN SPE species. Photon correlation measurements are consistent with a three-level model with weak coupling to a shelving state. Our ab initio excited-state calculations shed light on the atomic origin of this SPE defect, which consists of a pair of substitutional carbon atoms located at boron and nitrogen sites separated by a hexagonal unit cell.

This work reports simulated results and detector designs for a novel borehole detector consisting of cylindrically coupled custom-made plastic scintillator and BN:ZnS(Ag) thermal neutron converter foils. A monolithic detector was simulated within a mock borehole configuration under a 14 MeV pulsed neutron flux to test detector response to induced radiation from test materials. A data set was built up from simulations of 500 different test materials containing varying quantities of Carbon, Hydrogen, and Oxygen, and used to train several models to make predictions of Hydrogen content. Detector heatmaps (position and time-after-pulse) were used as training data. An example detector with 12 z-bins predicted H-content to within +/-1% in 58% of cases using random forests. Results showed that higher segmentation offers no significant advantage over conventional dual-binned detectors. This work will also report on manufacture and testing of custom-made plastic scintillator which will be coupled to BN:ZnS(Ag) thermal neutron converter foils as part of isolated detector modules.

Abstract Advances in nanoscale additive manufacturing (AM) offer great opportunities to expand nanotechnologies; however, the size effects in these printed remain largely unexplored. Using both in situ nanomechanical and electrical experiments and molecular dynamics (MD) simulations, this study investigates additively manufactured nano-architected nanocrystalline ZnO (nc-ZnO) with ∼7 nm grains and dimensions spanning 0.25–4 μ m. These nano-scale ceramics are fabricated through printing and subsequent burning of metal ion-containing hydrogels to produce oxide structures. Electromechanical behavior is shown to result from random ordering in the microstructure and can be modeled through a statistical treatment. A size effect in the failure behavior of AM nc-ZnO is also observed and characterized by the changes in deformation behavior and suppression of brittle failure. MD simulations provide insights to the role of grain boundaries and grain boundary plasticity on both electromechanical behavior and failure mechanisms in nc-ZnO. The frameworks developed in this paper extend to other AM nanocrystalline materials and provide quantification of microstructurally-drive limitations to precision in materials property design.

Studies on mechanical size effects in nanosized metals unanimously highlight both intrinsic microstructures and extrinsic dimensions for understanding size-dependent properties, commonly focusing on strengths of uniform microstructures, e.g., single-crystalline/nanocrystalline and nanoporous, as a function of pillar diameters, D . We developed a hydrogel infusion-based additive manufacturing (AM) technique using two-photon lithography to produce metals in prescribed 3D-shapes with ∼100 nm feature resolution. We demonstrate hierarchical microstructures of as-AM-fabricated Ni nanopillars ( D ∼ 130–330 nm) to be nanoporous and nanocrystalline, with d ∼ 30–50 nm nanograins subtending each ligament in bamboo-like arrangements and pores with critical dimensions comparable to d . In situ nanocompression experiments unveil their yield strengths, σ, to be ∼1–3 GPa, above single-crystalline/nanocrystalline counterparts in the D range, a weak size dependence, σ ∝ D –0.2, and localized-to-homogenized transition in deformation modes mediated by nanoporosity, uncovered by molecular dynamics simulations. This work highlights hierarchical microstructures on mechanical response in nanosized metals and suggests small-scale engineering opportunities through AM-enabled microstructures.

Additive manufacturing frees up the structural design of battery electrode materials from traditional slurry electrodes, enabling three-dimensional free-standing structures with micro-architected features, which provides a promising pathway toward 3D solid-state batteries with high power and high energy density. In this work, lithium cobalt oxide (LCO) is fabricated into 3D micro-lattice through a novel hydrogel infusion additive manufacturing (HIAM) process. A blank 3D architected organogel is fabricated through photopolymerization-based 3D printing and soaked in water to form a blank hydrogel micro-lattice, where lithium and cobalt ions in an aqueous solution are then swelled into the hydrogel. A free-standing LCO micro-lattice is synthesized from the ion-containing hydrogel during the post-printing calcination process. 50 μm beam diameter is obtained, giving a crucial lithium-ion diffusion length of 25 μm into LCO lattice beams. Structural, electrochemical, and mechanical properties of the LCO microlattice are investigated. HIAM technique utilizes photopolymerization of a UV-curable photoresin to create 3D structures with well-controlled form factors. Compared to traditional extrusion-based additive manufacturing techniques, photopolymerization stands out for its ability to fabricate materials with higher resolution. The main challenge with photopolymerization to fabricate non-polymeric functional materials is the complex photoresin design. A standard approach is to introduce active material nanoparticles into the photoresin, which often sacrifices print resolution due to the presence of light-scattering nanoparticles. HIAM technique overcomes the difficulties during the resin design by using a single photoresin to fabricate a large variety of functional materials. Without presence of nanoparticles, even higher resolution can be achieved. With this technique, LCO cathodes can be flexibly architected into 3D geometries for optimization of their electrochemical performance. It also enables the fabrication of various electrode materials into 3D structures with well-controlled form factors, and their incorporation into customizable batteries and microbatteries of any shape.

Abstract Additive manufacturing (AM) of metals can enable rapid development of functional parts of complex geometry, with potential applications in the aerospace, automotive, and biomedical fields [1–3]. Typical metal additive manufacturing techniques are based on expensive laser melting or sintering processes which are often highly anisotropic, limiting the development and use of these methods. Furthermore, few additive manufacturing techniques focus on high temperature materials, ceramics, and fabrication of machine elements. The recent introduction of Hydrogel-Infusion Additive Manufacturing (HIAM) may reduce some of these barriers, enabling potential applications in high performance metal and ceramic devices and components. The HIAM process involves 3D printing a polyethylene oxide (PEO) photo-resin using vat polymerization, immersing the polymer in a metal salt solution which allows ionized metal cations to bond to the polymer backbone, followed by calcination to combust the polymer leaving a metal oxide that takes the same functional structure as the original polymer. Finally, the metal oxide is reduced using a forming gas (95% N2/5% H2) to give a metal product that maintains a scaled-down version of the complex as-printed architecture. This technique enables architected features with microscale resolution by use of a single photoresin simply by varying post-processing conditions. As a first step in the fabrication of machine elements and devices, this paper outlines an attempt to fabricate springs made from silver metal via HIAM. Silver nitrate is infused into an additively manufactured polymer spring structure. Based on the relative differences in the standard free energy of the oxides, Silver Oxide (AgO) is readily reduced to metallic silver under a single thermal processing step: calcination/reduction at 500°C without the need for forming gas. A variety of analytical techniques confirm HIAM processing obeys chemical kinetics of single-step calcination and reduction in accordance with literature and results in fabricated components of low microstrain (8.40E−7 ± 2.78E−9) crystalline silver with average crystallite size of 514.95 ± 5.32 Å and lattice parameter of 4.09 ± 5.23E−5 Å. Thermal analyses such as Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) elucidate the mass loss and reactions that occur during the furnace processing. Springs were subjected to quasi-static and cyclic loading using a Dynamic Mechanical Analyzer (DMA). A range of ∼2–20 N/mm stiffness was measured in unloading for different coil diameters and produced springs show consistency of part stiffness following compaction under cyclic loading.

Lightweight and tough engineered materials are often designed with three-dimensional hierarchy and interconnected structural members whose junctions are detrimental to their performance because they serve as stress concentrations for damage accumulation and lower mechanical resilience. We introduce a previously unexplored class of architected materials, whose components are interwoven and contain no junctions, and incorporate micro-knots as building blocks within these hierarchical networks. Tensile experiments, which show close quantitative agreements with an analytical model for overhand knots, reveal that knot topology allows a new regime of deformation capable of shape retention, leading to a ~92% increase in absorbed energy and an up to ~107% increase in failure strain compared to woven structures, along with an up to ~11% increase in specific energy density compared to topologically similar monolithic lattices. Our exploration unlocks knotting and frictional contact to create highly extensible low-density materials with tunable shape reconfiguration and energy absorption capabilities.

Heterostructural Nanolattice Capacitors In article number 2208409, Julia R. Greer, Bong-Joong Kim, and co-workers demonstrate density-variant nanolattices that exhibit bi-phase deformation by which the lower-density region protects the higher-density region. This deformation improves the electrical breakdown strength by ≈3.3 fold of the uniform-density nanolattice, while maintaining the ultralow-k of ≈1.2 with complete electric and dielectric stability and recoverability during 100 cyclic compressions to 62.5% strain.

The multiscale structure of biomaterials enables their exceptional mechanical robustness, yet the impact of each constituent at their relevant length scale remains elusive. We used SAXD analysis to expose the intact chitin-fiber architecture within the exoskeleton on a scorpion's claw, revealing varying orientations, including Bouligand and unidirectional regions different from other arthropod species. We uncovered the contribution of individual components' constituent behavior to its mechanical properties from the micro- to the nanoscale. At the microscale, in-situ micromechanical experiments were used to determine site-specific stiffness, strength, and failure of the biocomposite due to fiber orientation, while metal-crosslinking of proteins is characterized via fluorescence maps. At the constituent level, combined with FEA simulations, we uncovered the behavior of fiber-matrix deformation with fiber diameter <53.7 nm and protein modulus in the range 1.4-11 MPa. The unveiled microstructure-mechanics relationship sheds light on the evolved structural functionalities and constituents' interactions within the scorpion cuticle. STATEMENT OF SIGNIFICANCE: : The pincer exoskeleton is a fundamental part of the scorpion's body due to its multifunctionality. Precise structural and compositional analysis within the hierarchy is paramount to understand the fundamentals of the mechanical properties of the composite exoskeleton. Here, we expose the intact chitin-fiber architecture of the pincer exoskeleton using nondestructive analysis. In-situ mechanical characterization was performed at nanometer levels within the exoskeleton hierarchy, which complemented with simulations, uncovered the elastic modulus of the protein matrix. Our findings confirm the presence and distribution of metal ions and their role as reinforcements in the protein matrix via ligand coordinate bonds. In future work, these findings can be of great potential to inspire the design of composite materials.

Abstract Nanoarchitected materials represent a class of structural meta‐materials that utilze nanoscale features to achieve unconventional material properties such as ultralow density and high energy absorption. A dearth of fabrication methods capable of producing architected materials with sub‐micrometer resolution over large areas in a scalable manner exists. A fabrication technique is presented that employs holographic patterns generated by laser exposure of phase metasurface masks in negative‐tone photoresists to produce 30–40 µm‐thick nanoarchitected sheets with 2.1 × 2.4 cm 2 lateral dimensions and ≈500 nm‐wide struts organized in layered 3D brick‐and‐mortar‐like patterns to result in ≈50–70% porosity. Nanoindentation arrays over the entire sample area reveal the out‐of‐plane elastic modulus to vary between 300 MPa and 4 GPa, with irrecoverable post‐elastic material deformation commencing via individual nanostrut buckling, densification within layers, shearing along perturbation perimeter, and tensile cracking. Laser induced particle impact tests (LIPIT) indicate specific inelastic energy dissipation of 0.51–2.61 MJ kg −1 , which is comparable to other high impact energy absorbing composites and nanomaterials, such as Kevlar/poly(vinyl butyral) (PVB) composite, polystyrene, and pyrolized carbon nanolattices with 23% relative density. These results demonstrate that holographic lithography offers a promising platform for scalable manufacturing of nanoarchitected materials with impact resistant capabilities.