Search NASA⌕ Search

SEARCH · Search NASA

Results for “BENDING”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Freestanding Photoresist Film: A Versatile Template for Three-Dimensional Micro- and Nanofabrication

Ultrathin freestanding films with well-defined micro/nanostructures and robust mechanical properties are applied in many engineering applications including microelectronics, optics, filtration and separation, biomedical engineering, and nanotechnology. Although considerable efforts have been made toward the fabrication of freestanding thin films, it is still a significant challenge to develop a simple and reliable process for producing freestanding films with ultrathin thickness, well-regulated micro/nanopatterns, robust mechanical properties, macroscopic coverage area, and multi-layered composite structures. In this work, a significant advancement is reported in this regard. This study shows a new sacrificial-layer-free (SLF) lifting-off process, integrated with conventional micro- and nanolithography, enabling the release of micro- and nanopatterned photoresist (PR) films from the supporting substrate with unprecedented pattern coverage and structure characteristics. The freestanding PR film is resilient, can withstand significant bending and deformation, and is sufficiently flexible to be transferred onto substrates with 3D topography as a conformal soft stencil for further technological processing and applications. Moreover, the SLF lifting-off process provides a simple approach to prepare single-layered and multi-layered freestanding composite films. The results suggest that the novel SLF lifting-off process can significantly extend the capability of 3D micro-/nanofabrication.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Structural Design Variations in Beetle Elytra

Abstract Beetles typically use their protective wing coverings or elytra to shield their membranous hindwings from the environment. Elytra in some terrestrial species have evolved a greater protective role capable of shielding the organism from powerful antagonistic predators. The structure–function relationships of these biological composites identify how architectural and chemical variations of the cuticle are tuned to create light‐weight, impact resistant composites. Specifically, the elytral structures of a tree dwelling beetle capable of flight, Trypoxylus dichotomus , and a terrestrial beetle incapable of flight, Phloeodes diabolicus , are compared to understand how their varied environmental needs forged the elytra to facilitate fight or resist fatal predator strikes. Mechanical and microstructural analysis reveals P . diabolicus has a harder, stiffer elytra that incorporate through‐thickness fibers to resist greater mechanical stresses imposed by bending and puncture. Conversely, the elytra of T . dichotomus have a compliant structure with large voids that facilitates localized deformation. Variations in flexural strength and puncture resistance remain attributed to P . diabolicus possessing a thicker cuticle with a greater degree of cross‐linking and an increased amount of endocuticular layers. These findings may provide useful insight into the design and manufacturing of composite materials for use in light‐weight or energy‐absorbing applications.

Rivera, Jesus↗
DOE OSTI2022

Unprecedented Multifunctionality in 1D Nb 1- x Ta x S 3 Transition Metal Trichalcogenide Alloy

One-dimensional (1D) van der Waals materials, such as nanofibers or nanoribbons are considered as the future ultimate limit of downscaling for modern electrical and electrochemical devices. Here, for the first time, we successfully synthesize nanofibers of a solid solution transition metal trichalcogenide (TMTC), Nb 1-x Ta x S 3 , with outstanding electrical, thermal, and electrochemical characteristics rivaling the performance of the-state-of-the art materials for each application. This material shows nearly unchanged sheet resistance (≈740 Ω/sq -1 ) versus bending cycles tested up to 90 cycles, stable sheet resistance in ambient conditions tested up to 60 days, remarkably high electrical breakdown current density of ≈ 30 MA cm -2 , strong evidence of successive charge density wave (CDW) transitions, and outstanding thermal stability up to ≈900 K. Additionally, this material demonstrates excellent activity and selectivity for CO2 conversion to CO reaching ≈ 350 mA cm -2 at – 0.8 V vs RHE with an outstanding turnover frequency number of 25 for CO formation. It also exhibits an excellent performance in a high-rate Li-air battery with the specific capacity of 3000 mAhg -1 at a high current density of 0.3 mAcm -2 . This study uncovers the multifunctionality in 1D TMTC alloys for a wide range of high-impact applications and opens a new direction for the design of the next generation of low-dimensional materials with high performance.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Formation and Shape Changing of Conductive Helical Ribbons via Deposition of Highly Stressed Films on Mechanically Responsive Substrates

Abstract This work demonstrates that the electrodeposition of highly stressed films on compliant ribbons is a robust process to obtain helical structures with excellent mechanical stability and potentially high thermal and electrical conductance. Electrodeposition on end‐tethered ribbons alters their axial and bending stiffness while imparting mechanical stress to drive the formation of a helix with a microscale diameter and pitch in a controlled and scalable manner. The process generates helices with diameters and pitches between 80 and 200 µm and lengths as large as several millimeters. The approach is amenable to parallel processing a large number of 3D structures on any substrate, including large‐area semiconductor wafers. This phenomenon is explained in terms of the change of stress gradients as material is added. Applications of the fabricated helices include antennas, metamaterials, and slow‐wave structures in frequency ranges not previously attainable.

Chemistry↗
DOE OSTI2025

Boron‐Doped Nano‐Crystalline Coated Carbon Fibers for Phasic Dopamine Sensing

Real time, chronic electrochemical detection of neurotransmitters will provide a positive step in the treatment and understanding of neurological disease. However, current electrodes using carbon fibers (CF) fail to perform chronically. While diamond-based coatings show promise in improving their longevity, achieving a uniform layer of such coatings on CFs is challenging, and the electrodes often lose sensitivity after coating. In this work, a complete and uniform boron-doped nanocrystalline material grown in a diamond reactor (B-NCD) was developed to coat CF microelectrodes for neurochemical sensing. The coating was characterized electrically, optically, mechanically, and chemically. The B-NCD coated CF electrodes were able to detect phasic dopamine at a sensitivity comparable to the most widely used alternatives (uncoated and PEDOT:Nafion coated CFs). During biofouling testing, the B-NCD coated CF electrodes demonstrated better stability than uncoated CFs and comparable performance to PEDOT:Nafion coated CFs. Moreover, B-NCD exhibited no signs of degradation during consecutive FSCV applications, while uncoated and PEDOT:Nafion coated CF electrodes degraded significantly over time. Furthermore, the B-NCD coating supported the survival and development of neurons and astrocytes in vitro, exhibited excellent adhesion and durability during mechanical bending testing, and enabled successful in vivo recording of phasic dopamine release in the rat brain. Overall, B-NCD coated CFs present as an ideal candidate for chronic, flexible neural implantable electrodes for long-term neurochemical monitoring.

carbon fiber↗
DOE OSTI2021

Synergistic Enzyme Mixtures to Realize Near-Complete Depolymerization in Biodegradable Polymer/Additive Blends

Embedding catalysts inside of plastics affords accelerated chemical modification with programmable latency and pathways. Nanoscopically embedded enzymes can lead to near-complete degradation of polyesters via chain-end mediated processive depolymerization. The overall degradation rate and pathways have a strong dependence on the morphology of semicrystalline polyesters. Yet, most studies to date focus on pristine polymers instead of mixtures that contain additives and other components despite their nearly universal use in plastic production. Here, for this study, additives are introduced to purposely change the morphology of polycaprolactone (PCL) by increasing the bending and twisting of crystalline lamellae. These morphological changes immobilize chain ends preferentially at the crystalline/amorphous interfaces and limit chain-end accessibility by the embedded processive enzyme. This chain-end redistribution reduces the polymer-to-monomer conversion from >95% to less than 50%, causing formation of highly crystalline plastic pieces, including microplastics. By synergizing both random chain scission and processive depolymerization, it is feasible to navigate morphological changes in polymer/additive blends and to achieve near-complete depolymerization. The random scission enzymes in the amorphous domains create new chain ends that are subsequently bound and depolymerized by processive enzymes. Present studies further highlight the importance to consider how the host polymer's morphologies affect the reactions catalyzed by embedded catalytic species.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Elucidating and Mitigating High-Voltage Degradation Cascades in Cobalt-Free LiNiO 2 Lithium-Ion Battery Cathodes

LiNiO 2 (LNO) is a promising cathode material for next-generation Li-ion batteries due to its exceptionally high capacity and cobalt-free composition that enables more sustainable and ethical large-scale manufacturing. However, its poor cycle life at high operating voltages over 4.1 V impedes its practical use, thus motivating efforts to elucidate and mitigate LiNiO 2 degradation mechanisms at high states of charge. Here, a multiscale exploration of high-voltage degradation cascades associated with oxygen stacking chemistry in cobalt-free LiNiO 2 , is presented. In this work, lattice oxygen loss is found to play a critical role in the local O3–O1 stacking transition at high states of charge, which subsequently leads to Ni-ion migration and irreversible stacking faults during cycling. This undesirable atomic-scale structural evolution accelerates microscale electrochemical creep, cracking, and even bending of layers, ultimately resulting in macroscopic mechanical degradation of LNO particles. By employing a graphene-based hermetic surface coating, oxygen loss is attenuated in LNO at high states of charge, which suppresses the initiation of the degradation cascade and thus substantially improves the high-voltage capacity retention of LNO. Overall, this study provides mechanistic insight into the high-voltage degradation of LNO, which will inform ongoing efforts to employ cobalt-free cathodes in Li-ion battery technology.

25 ENERGY STORAGE↗
DOE OSTI2022

Dual–Interface–Reinforced Flexible Perovskite Solar Cells for Enhanced Performance and Mechanical Reliability

Two key interfaces in flexible perovskite solar cells (f-PSCs) are mechanically reinforced simultaneously: one between the electron-transport layer (ETL) and the 3D metal-halide perovskite (MHP) thin film using self-assembled monolayer (SAM), and the other between the 3D-MHP thin film and the hole-transport layer (HTL) using an in situ grown low-dimensional (LD) MHP capping layer. The interfacial mechanical properties are measured and modeled. This rational interface engineering results in the enhancement of not only the mechanical properties of both interfaces but also their optoelectronic properties holistically. As a result, the new class of dual-interface-reinforced f-PSCs has an unprecedented combination of the following three important performance parameters: high power-conversion efficiency (PCE) of 21.03% (with reduced hysteresis), improved operational stability of 1000 h T90 (duration at 90% initial PCE retained), and enhanced mechanical reliability of 10 000 cycles n88 (number of bending cycles at 88% initial PCE retained). Furthermore, the scientific underpinnings of these synergistic enhancements are elucidated.

14 SOLAR ENERGY↗
DOE OSTI2022

Emergent Magnetic States and Tunable Exchange Bias at 3d Nitride Heterointerfaces

Abstract Interfacial magnetism stimulates the discovery of giant magnetoresistance (MR) and spin–orbital coupling across the heterointerfaces, facilitating the intimate correlation between spin transport and complex magnetic structures. Over decades, functional heterointerfaces composed of nitrides have seldom been explored due to the difficulty in synthesizing high‐quality nitride films with correct compositions. Here, the fabrication of single‐crystalline ferromagnetic Fe 3 N thin films with precisely controlled thicknesses is reported. As film thickness decreases, the magnetization dramatically deteriorates, and the electronic state changes from metallic to insulating. Strikingly, the high‐temperature ferromagnetism is maintained in a Fe 3 N layer with a thickness down to 2 u.c. (≈8 Å). The MR exhibits a strong in‐plane anisotropy; meanwhile, the anomalous Hall resistivity reverses its sign when the Fe 3 N layer thickness exceeds 5 u.c. Furthermore, a sizable exchange bias is observed at the interfaces between a ferromagnetic Fe 3 N and an antiferromagnetic CrN. The exchange bias field and saturation moment strongly depend on the controllable bending curvature using the cylinder diameter engineering technique, implying the tunable magnetic states under lattice deformation. This work provides a guideline for exploring functional nitride films and applying their interfacial phenomena for innovative perspectives toward practical applications.

Jin, Qiao↗
DOE OSTI2024

Carboxylating Elastomer via Thiol‐Ene Click Reaction to Improve Miscibility with Conjugated Polymers for Mechanically Robust Organic Solar Cells with Efficiency of 19%

Abstract Incorporating flexible insulating polymers is a straightforward strategy to enhance the mechanical properties of rigid conjugated polymers, enabling their use in flexible electronic devices. However, maintaining electronic characteristics simultaneously is challenging due to the poor miscibility between insulating polymers and conjugated polymers. This study introduces the carboxylation of insulating polymers as an effective strategy to enhance miscibility with conjugated polymers via surface energy modulation and hydrogen bonding. The carboxylated elastomer, synthesized via a thiol‐ene click reaction, closely matches the surface energy of the conjugated polymer. This significantly improves the mechanical properties, achieving a high crack‐onset strain of 21.48%, surpassing that (5.93%) of the unmodified elastomer:conjugated polymer blend. Upon incorporating the carboxylated elastomer into PM6:L8‐BO‐based organic solar cells, an impressive power conversion efficiency of 19.04% is attained, which top‐performs among insulating polymer‐incorporated devices and outperforms devices with unmodified elastomer or neat PM6:L8‐BO. The superior efficiency is attributed to the optimized microstructures and enhanced crystallinity for efficient and balanced charge transport, and suppressed charge recombination. Furthermore, flexible devices with 5% carboxylated elastomer exhibit superior mechanical stability, retaining ≈88.9% of the initial efficiency after 40 000 bending cycles at a 1 mm radius, surpassing ≈83.5% for devices with 5% unmodified elastomer.

Chemistry↗
DOE OSTI2023

Transitional Structures with Continuous Variations in Atomic Positions from Anatase to Rutile Improve Photocatalytic Activity

Abstract TiO 2 polymorphs have distinct properties that are widely employed in various applications. However, mechanisms of transformations between these polymorphs are not fully understood, especially at atomic scale, inhibiting advancing the design and application of the transitional phases. Here, based on results from semi‐in situ transmission electron microscopy, density functional theory, and X‐ray photoemission experiments, a physical picture of transitional structures is discovered, in which continuous variations in atomic positions form along a previously unreported anatase‐to‐rutile phase transformation path of [010] A –to–[] R and (004) A –to– (011) R . These gradient structures give rise to continuous band bending, which promotes electron‐hole separation and inhibits their recombination across the bulk of the particles, leading to a large functionally active volume fraction and resulting in high photoactivity. These findings suggest that interphase matter based on extended gradient structures can be designed to advance new functions not achievable using abrupt interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Two–Photon Printing of Shape–Memory Microstructures and Metasurfaces via Radical–Mediated Thiol–Vinyl Hydrothiolation

Shape-memory resists capable of high-resolution curing into arbitrarily designed structures are increasingly demanded for soft robotics, optical sensors, microscale manufacturing, and biomedicine. Amorphous, shape-memory thiol-vinyl networks were printed using two-photon polymerization (2PP) curing of a simple resin formulated with commercially available reagents. The ability to print high-resolution feature sizes down to 200 nm is attributed to the use of radicalmediated, thiol-vinyl step-growth polymerization that quickly crosslinks the resin, limiting diffusive transport. The thermomechanical behavior of the 2PP-cured material analyzed in compression, tension and three-point bending is similar to the behavior of the UV-polymerized samples. To demonstrate the ability to design, field, and test 4D responsive microstructures, an array of nine springs with coil diameters of 330 μm was printed. Following compressive shapefixing, printed arrays can release 11 μJ of stored elastic strain energy when reheated. Further, a new concept of dichroic-memory of a metamaterial device is demonstrated by printing a twisted woodpile structure with circular dichroism as characterized by Mueller Matrix ellipsometry. Furthermore, our results demonstrate how combining high-resolution 2PP curing with stimuli-responsive molecular architectures can further the engineering of responsive microstructures and metamaterials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A Flexible, Redox-Active, Aqueous Electrolyte-Based Asymmetric Supercapacitor with High Energy Density Based on Keratin-Derived Renewable Carbon

This work exploits the advantage of asymmetric configuration over symmetric supercapacitor in designing high energy density flexible devices from two active electrode materials–keratin-based renewable-resource hierarchically porous carbon and hydrous ruthenium oxide (RuO 2 ). Here, the asymmetric device exhibits significantly high capacitance. Conventional estimation of energy storage parameters, however, cannot be applied for devices with a Faradaic energy storage contribution via redox charge transfer mechanism. Therefore, this work applies a precise measurement of pseudocapacitance contribution at various scan rates to correct the device data that reveals effective capacitance of 120 F g –1 with the energy density of 37 W h kg –1 at 776 W kg –1 . It also retains excellent rate capability, >74% at high current density 25 A g –1 . The charge storage activity and device stability can be further enhanced by introducing redox-active electrolytes that improve specific capacitance, but the rate capabilities deteriorate at high current densities. Further, the principle of asymmetric electrode design is applied to fabricate a bending-tolerant, flexible device by depositing active electrode material on wire-shaped current collector followed by coupling those separated with polyvinyl alcohol gel containing redox electrolyte; it yields 36.8 mF cm –1 specific capacitance at a 0.2 mA cm –1 current density.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Mechanical Consequences of Oxygen Inhibition in Vat Polymerization

Vat polymerization is a type of additive manufacturing that is used extensively to produce micro-architected structures for mechanical applications, which brings the mechanical properties of photopolymerized resins into sharp focus. However, it is known that photopolymerization is sensitive to a number of factors, perhaps the most notorious of which is oxygen inhibition. Herein, the degree to which oxygen inhibition influences the macroscopic and microscopic properties of structures made using vat polymerization is explored. This work is motivated by an observation of lattices being >4 times softer in the experiment than predicted by simulation, which is hypothesized to be due to the material at the surface being incompletely cured. Furthermore, this hypothesis is supported by four-point bending tests in which flexural modulus is found to increase with beam thickness. Nanoindentation and bulk compression studies show that this surface softening is present for three distinct resins. Importantly, it is observed that structures post-print cured in nitrogen are stiffer than those post-print cured in air, however, regardless of the post-print curing environment, printing samples in the presence of oxygen makes them softer than samples photocured in nitrogen. Collectively, these results show the outsized influence of oxygen inhibition on micro-architected structures realized using vat polymerization.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Reconfigurable Magnetic Liquid Building Blocks for Constructing Artificial Spinal Column Tissues

All-liquid molding can be used to transform a liquid into free-form solid constructs, while maintaining internal fluidity. Traditional biological scaffolds, such as cured pre-gels, are normally processed in solid state, sacrificing flowability and permeability. However, it is essential to maintain the fluidity of the scaffold to truly mimic the complexity and heterogeneity of natural human tissues. Here, this work molds an aqueous biomaterial ink into liquid building blocks with rigid shapes while preserving internal fluidity. The molded ink blocks for bone-like vertebrae and cartilaginous-intervertebral-disc shapes, are magnetically manipulated to assemble into hierarchical structures as a scaffold for subsequent spinal column tissue growth. It is also possible to join separate ink blocks by interfacial coalescence, different from bridging solid blocks by interfacial fixation. Generally, aqueous biomaterial inks are molded into shapes with high fidelity by the interfacial jamming of alginate surfactants. The molded liquid blocks can be reconfigured using induced magnetic dipoles, that dictated the magnetic assembly behavior of liquid blocks. The implanted spinal column tissue exhibits a biocompatibility based on in vitro seeding and in vivo cultivating results, showing potential physiological function such as bending of the spinal column.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

Construction of Reconfigurable and Polymorphic DNA Origami Assemblies with Coiled‐Coil Patches and Patterns

Abstract DNA origami nanodevices achieve programmable structure and tunable mechanical and dynamic properties by leveraging the sequence‐specific interactions of nucleic acids. Previous advances have also established DNA origami as a useful building block to make well‐defined micron‐scale structures through hierarchical self‐assembly, but these efforts have largely leveraged the structural features of DNA origami. The tunable dynamic and mechanical properties also provide an opportunity to make assemblies with adaptive structures and properties. Here the integration of DNA origami hinge nanodevices and coiled‐coil peptides are reported into hybrid reconfigurable assemblies. With the same dynamic device and peptide interaction, it is made multiple higher‐order assemblies (i.e., polymorphic assembly) by organizing clusters of peptides into patches or arranging single peptides into patterns on the surfaces of DNA origami to control the relative orientation of devices. The coiled‐coil interactions are used to construct circular and linear assemblies whose structure and mechanical properties can be modulated with DNA‐based reconfiguration. Reconfiguration of linear assemblies leads to micron scale motions and ≈2.5‐10‐fold increase in bending stiffness. The results provide a foundation for stimulus‐responsive hybrid assemblies that can adapt their structure and properties in response to nucleic acid, peptide, protein, or other triggers.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Transfer of Millimeter‐Scale Strained Multiferroic Epitaxial Thin Films on Rigid Substrates via an Epoxy Method Producing Magnetic Property Enhancement

The demonstration of epitaxial thin film transfer has enormous potential for thin film devices free from the traditional substrate epitaxy limitations. However, large-area continuous film transfer remains a challenge for the commonly reported polymer-based transfer methods due to bending and cracking during transfer, especially for highly strained epitaxial thin films. In this work, a new epoxy-based, rigid transfer method is used to transfer films from an SrTiO 3 (STO) growth substrate onto various new substrates, including those that will typically pose significant problems for epitaxy. An epitaxial multiferroic Bi 3 Fe 2 Mn 2 O x (BFMO) layered supercell (LSC) material is selected as the thin film for this demonstration. The results of surface and structure studies show an order of magnitude increase in the continuous area of transferred films when compared to previous transfer methods. The magnetic properties of the BFMO LSC films are shown to be enhanced by the release of strain in this method, and ferromagnetic resonance is found with an exceptionally low Gilbert damping coefficient. The large-area transfer of this highly strained complex oxide BFMO thin film presents enormous potential for the integration of many other multifunctional oxides onto new substrates for future magnetic sensors and memory devices.

bismuth oxides↗