Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “robustness”

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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Robust Atomic-Resolution Imaging of Lithium in Battery Materials by Center-of-Mass Scanning Transmission Electron Microscopy

The performance of energy storage materials is often governed by their structure at the atomic scale. Conventional electron microscopy can provide detailed information about materials at these length scales, but direct imaging of light elements such as lithium presents a challenge. While several recent techniques allow lithium columns to be distinguished, these typically either involve complex contrast mechanisms that make image interpretation difficult or require significant expertise to perform. In this work, we demonstrate how center-of-mass scanning transmission electron microscopy (CoM-STEM) provides an enhanced ability for simultaneous imaging of lithium and heavier element columns in lithium ion conductors. Through a combination of experiments and multislice electron scattering calculations, we show that CoM-STEM is straightforward to perform and produces directly interpretable contrast for thin samples, while being more robust to variations in experimental parameters than previously demonstrated techniques. As a result, CoM-STEM is positioned to become a reliable and facile method for directly probing all elements within energy storage materials at the atomic scale.

25 ENERGY STORAGE↗
DOE OSTI2017

TlSn 2 I 5 , a Robust Halide Antiperovskite Semiconductor for γ-Ray Detection at Room Temperature

The semiconductor TlSn 2 I 5 with a two-dimensional crystal structure and an antiperovskite topology is a promising novel detection material. The compound crystallizes in the I4/mcm space group, has an indirect band gap of 2.14 eV, and melts congruently at 314 °C. Electronic band structure calculations reveal that the most facile electron transport is along the ab layered plane. Compared to CH 3 NH 3 PbX 3 (X = Br, I), TlSn 2 I 5 features higher long-term stability, higher photon stopping power (average atomic number of 55), higher resistivity (~10 10 Ω·cm), and robust mechanical properties. Centimeter-size TlSn 2 I 5 single crystals grown from the melt by the Bridgman method can be used to fabricate detector devices, which detect Ag Kα X-rays (22 keV), 57 Co γ-rays (122 keV), and 241 Am α-particles (5.5 MeV). The mobility-lifetime product and mobility for electrons were estimated to be 1.1 × 10 -3 cm 2 ·V -1 and 94 ± 16 cm 2 ·V -1 ·s -1 , respectively. Unlike other halide perovskites, TlSn 2 I 5 shows no signs of ionic polarization under long-term, high-voltage bias.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Delivering Robust Proton-Only Sensing of Hyperpolarized [1,2- 13 C 2 ]-Pyruvate Using Broad-Spectral-Range Nuclear Magnetic Resonance Pulse Sequences

Hyperpolarized [1- 13 C]pyruvate is the leading hyperpolarized injectable contrast agent and is currently under evaluation in clinical trials for molecular imaging of metabolic diseases, including cardiovascular disease and cancer. One aspect limiting broad scalability of the technique is that hyperpolarized 13 C MRI requires specialized 13 C hardware and software that are not generally available on clinical MRI scanners, which employ proton-only detection. Here, we present an approach that uses pulse sequences to transfer 13 C hyperpolarization to methyl protons for detection of the 13 C– 13 C pyruvate singlet, employing proton-only excitation and detection only. The new pulse sequences are robust to the B 1 and B 0 magnetic field inhomogeneities. The work focuses on singlet-to-magnetization (S2M) and rotor-synchronized (R) pulses, both relying on trains of hard pulses with broad spectral width coverage designed to effectively transform hyperpolarized 13 C 2 -singlet hyperpolarization to 1 H polarization on the CH 3 group of [1,2- 13 C 2 ]pyruvate. Finally, this approach may enable a broader adoption of hyperpolarized MRI as a molecular imaging technique.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Highly Selective Heterogeneous Ethylene Dimerization with a Scalable and Chemically Robust MOF Catalyst

Metal–organic frameworks (MOFs) hold great promise as structurally tunable catalysts capable of high selectivity in the solid state, yet their comparatively high cost and often limited stability remain significant concerns for their commercialization as heterogeneous catalysts. In this paper, we report detailed X-ray absorption spectroscopy studies of Co- and Ni-MFU-4$l$, a class of highly selective MOF catalysts for olefin upgrading, and reveal mechanisms that lead to their deactivation. We further show that Ni-CFA-1, a more scalable and economical alternative to Ni-MFU-4l, reproduces both the local coordination structure and the high selectivity of the latter in ethylene dimerization catalysis. Under optimal conditions, Ni-CFA-1 activated by MMAO-12 achieves a turnover frequency of 37100 per hour and a selectivity of 87.1% for 1-butene, a combination of activity, selectivity, and affordability that is unmatched among heterogeneous ethylene dimerization catalysts. Ni-CFA-1 retains its high activity for at least 12 h in a one-liter semibatch reactor, offering a strategy toward robust and scalable MOFs for industrial catalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Scrambling Signal Modularity in Bottom-up Assembled Synthetic Pseudomonas Consortia Reveals Robust Information Transfer

There is immense potential in crafting synthetic microbial communities for application in human health, agriculture, the environment, and even biomanufacturing where an appropriately constructed consortium can be assembled with tremendous biosynthetic or degradative capabilities. In many of these cases, bacterial signaling serves as a form of intercellular information transfer that guides the collective’s behavior. Such communication is complex, as many signals, signal disruptors, microbial species, physical barriers, and spatiotemporal constraints may be involved. Here, in this work, we demonstrate that a multisignal pathway for molecular information transfer within a consortium of several Pseudomonas spp. can be scrambled (genetically and organizationally) while the original message is still effectively conveyed. Assembled from the bottom up, we have employed two types of signaling molecules (i) a redox active secondary metabolite (rhizospheric signal, phloroglucinol), and (ii) a bacterial quorum sensing signal (3-oxo-C12 acylhomoserine lactone, AI-1). These signals can be intraconverted and acted upon by designated community members. We show how the order in which the signals are received, transduced, and subsequently transmitted can be rearranged with minimal impact on the intended outcome. In the consortial context, we found this messaging structure can be remarkably robust. Inspired by rhizospheric molecular signaling mechanisms, this work provides a conceptual framework for designing signaling and information transfer processes within assembled communities.

Biological and medical sciences↗
DOE OSTI2014

Reusable Oxidation Catalysis Using Metal-Monocatecholato Species in a Robust Metal–Organic Framework

An isolated metal-monocatecholato moiety has been achieved in a highly robust metal–organic framework (MOF) by two fundamentally different postsynthetic strategies: postsynthetic deprotection (PSD) and postsynthetic exchange (PSE). Compared with PSD, PSE proved to be a more facile and efficient functionalization approach to access MOFs that could not be directly synthesized under solvothermal conditions. Metalation of the catechol functionality residing in the MOFs resulted in unprecedented Fe-monocatecholato and Cr-monocatecholato species, which were characterized by X-ray absorption spectroscopy, X-band electron paramagnetic resonance spectroscopy, and ⁵⁷Fe Mössbauer spectroscopy. The resulting materials are among the first examples of Zr(IV)-based UiO MOFs (UiO = University of Oslo) with coordinatively unsaturated active metal centers. Importantly, the Cr-metalated MOFs are active and efficient catalysts for the oxidation of alcohols to ketones using a wide range of substrates. Catalysis could be achieved with very low metal loadings (0.5–1 mol %). Unlike zeolite-supported, Cr-exchange oxidation catalysts, the MOF-based catalysts reported here are completely recyclable and reusable, which may make them attractive catalysts for ‘green’ chemistry processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Robust, Chiral, and Porous BINAP-Based Metal–Organic Frameworks for Highly Enantioselective Cyclization Reactions

We report here the design of BINAP-based metal–organic frameworks and their postsynthetic metalation with Rh complexes to afford highly active and enantioselective single-site solid catalysts for the asymmetric cyclization reactions of 1,6-enynes. Robust, chiral, and porous Zr-MOFs of UiO topology, BINAP-MOF (I) or BINAP-dMOF (II), were prepared using purely BINAP-derived dicarboxylate linkers or by mixing BINAP-derived linkers with unfunctionalized dicarboxylate linkers, respectively. Upon metalation with Rh(nbd)2BF4 and [Rh(nbd)Cl]2/AgSbF6, the MOF precatalysts I·Rh(BF4) and I·Rh(SbF6) efficiently catalyzed highly enantioselective (up to 99% ee) reductive cyclization and Alder-ene cycloisomerization of 1,6-enynes, respectively. I·Rh catalysts afforded cyclization products at comparable enantiomeric excesses (ee’s) and 4–7 times higher catalytic activity than the homogeneous controls, likely a result of catalytic site isolation in the MOF which prevents bimolecular catalyst deactivation pathways. However, I·Rh is inactive in the more sterically encumbered Pauson–Khand reactions between 1,6-enynes and carbon monoxide. In contrast, with a more open structure, Rh-functionalized BINAP-dMOF, II·Rh, effectively catalyzed Pauson–Khand cyclization reactions between 1,6-enynes and carbon monoxide at 10 times higher activity than the homogeneous control. II·Rh was readily recovered and used three times in Pauson–Khand cyclization reactions without deterioration of yields or ee’s. Our work has expanded the scope of MOF-catalyzed asymmetric reactions and showed that the mixed linker strategy can effectively enlarge the open space around the catalytic active site to accommodate highly sterically demanding polycyclic metallocycle transition states/intermediates in asymmetric intramolecular cyclization reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Confinement of Iodine Molecules into Triple-Helical Chains within Robust Metal–Organic Frameworks

During nuclear waste disposal process, radioactive iodine as a fission product can be released. The widespread implementation of sustainable nuclear energy thus requires the development of efficient iodine stores that have simultaneously high capacity, stability and more importantly, storage density (and hence minimized system volume). Here, we report high I 2 adsorption in a series of robust porous metal–organic materials, MFM-300(M) (M = Al, Sc, Fe, In). MFM-300(Sc) exhibits fully reversible I 2 uptake of 1.54 g g –1 , and its structure remains completely unperturbed upon inclusion/removal of I 2 . Direct observation and quantification of the adsorption, binding domains and dynamics of guest I 2 molecules within these hosts have been achieved using XPS, TGA-MS, high resolution synchrotron X-ray diffraction, pair distribution function analysis, Raman, terahertz and neutron spectroscopy, coupled with density functional theory modeling. These complementary techniques reveal a comprehensive understanding of the host–I 2 and I 2 –I 2 binding interactions at a molecular level. The initial binding site of I 2 in MFM-300(Sc), I 2 I , is located near the bridging hydroxyl group of the [ScO 4 (OH) 2 ] moiety [I 2 I ···H–O = 2.263(9) Å] with an occupancy of 0.268. I 2 II is located interstitially between two phenyl rings of neighboring ligand molecules [I 2 II ···phenyl ring = 3.378(9) and 4.228(5) Å]. I 2 II is 4.565(2) Å from the hydroxyl group with an occupancy of 0.208. Significantly, at high I 2 loading an unprecedented self-aggregation of I 2 molecules into triple-helical chains within the confined nanovoids has been observed at crystallographic resolution, leading to a highly efficient packing of I 2 molecules with an exceptional I 2 storage density of 3.08 g cm –3 in MFM-300(Sc).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Blending Ionic and Coordinate Bonds in Hybrid Semiconductor Materials: A General Approach toward Robust and Solution-Processable Covalent/Coordinate Network Structures

Inorganic semiconductor materials are best known for their superior physical properties, as well as their structural rigidity and stability. However, the poor solubility and solution-processability of these covalently bonded network structures has long been a serious drawback that limits their use in many important applications. Here, we present a unique and general approach to synthesize robust, solution-processable, and highly luminescent hybrid materials built on periodic and infinite inorganic modules. Structure analysis confirms that all compounds are composed of one-dimensional anionic chains of copper iodide (Cu m I m+2 2- ) coordinated to cationic organic ligands via Cu-N bonds. The choice of ligands plays an important role in the coordination mode (μ 1 -MC or μ 2 -DC) and Cu-N bond strength. Greatly suppressed nonradiative decay is achieved for the μ 2 -DC structures. Record high quantum yields of 85% (λ ex = 360 nm) and 76% (λ ex = 450 nm) are obtained for an orange-emitting 1D-Cu 4 I 6 (L 6 ). Temperature dependent PL measurements suggest that both phosphorescence and thermally activated delayed fluorescence contribute to the emission of these 1D-AIO compounds, and that the extent of nonradiative decay of the μ 2 -DC structures is much less than that of the μ1 -DC structures. More significantly, all compounds are remarkably soluble in polar aprotic solvents, distinctly different from previously reported CuI based hybrid materials made of charge-neutral Cu m X m (X = Cl, Br, I), which are totally insoluble in all common solvents. Finally, the greatly enhanced solubility is a result of incorporation of ionic bonds into extended covalent/coordinate network structures, making it possible to fabricate large scale thin films by solution processes

36 MATERIALS SCIENCE↗
DOE OSTI2026

A Robust Methodology to Elucidate Kinetics of Room Temperature Electrochemical Propane Adsorption on Platinum

Electrocatalytic activation of alkanes can further decarbonize chemical manufacturing by leveraging affordable renewable electricity and readily available shale gas reserves in the United States. Earlier works have identified the unique role of Pt in adsorbing and activating alkanes, like propane, at room temperature in acidic, aqueous electrolytes, revealing spontaneous formation of deeply dehydrogenated propane-derived surface species with an intact C 3 - backbone. Although an adsorption mechanism was hypothesized, it has not been explicitly investigated to date, preventing the quantification of kinetic rate parameters. A robust methodology to investigate and benchmark propane adsorption kinetics on Pt is critical for the rational design of electrocatalysts that exhibit higher selectivity toward desired partially oxidized products. Herein, we analyze an oxidative current transience that appears during the adsorption of propane on Pt in aqueous electrochemical conditions and develop a methodology that elucidates the adsorption mechanism and enables quantification of rate parameters such as order dependences and apparent activation barriers. This method yields an expected first-order dependence with respect to propane concentration at low coverage and reveals a second-order dependence with respect to the concentration of surface active sites. Additionally, the apparent activation barrier for propane adsorption was calculated using an Arrhenius analysis of the current transience under temperature control. The experimentally measured activation barrier of 35 kJ mol –1 is in excellent agreement with the theoretical barrier calculated by density functional theory (DFT). The kinetic analysis was extended, via the use of transition state theory, to extract entropy and enthalpy of activation, yielding consistent results with the proposed two-step adsorption mechanism and DFT calculations. These results demonstrate reliable quantification of kinetic parameters for electrocatalytic activation of C–H bonds in alkanes that can be employed for rational catalyst development for a versatile range of electrocatalytic conditions.

alkane activation↗
DOE OSTI2026

Robust Automatic EXAFS First-Shell Fits

Extended X-ray absorption fine structure (EXAFS) is a widely used technique for atomic structure determination. Fourier transformation connects EXAFS in k space and R space. However, determining the appropriate k-range for the transformation can be challenging, but critical for the first-shell fit. In this study, we present an automatic method to determine the k-range using the Larch package and a Python program. The first step is to estimate spectral noise across a series of k-ranges with a fixed minimum value and identify the optimal maximum value in the k-range (k max ). The k max is determined by an empirical noise threshold that marks the point where the noise level in the Fourier transformed spectrum changes dramatically. Using the obtained k max value, the first shell is modeled to determine the minimum k value (k min ) by optimizing the background function through alignment of the spectrum with theory. The optimal k min corresponds to the point of the minimum R-factor, which quantifies the difference between the experimental and fitted spectrum. Our method was tested on various typical datasets and yielded suitable k-ranges for Fourier transformation and accurate first-shell fits. This approach helps avoid unreliable, irreproducible data analysis, especially for noisy data from diluted samples, and enables robust automatic first-shell EXAFS fitting.

EXAFS analysis↗
DOE OSTI2020

Robust Multiyear Climate Impacts of Volcanic Eruptions in Decadal Prediction Systems

Abstract Major tropical volcanic eruptions have a large impact on climate, but there have only been three major eruptions during the recent relatively well‐observed period. Models are therefore an important tool to understand and predict the impacts of an eruption. This study uses five state‐of‐the‐art decadal prediction systems that have been initialized with the observed state before volcanic aerosols are introduced. The impact of the volcanic aerosols is found by subtracting the results of a reference experiment where the volcanic aerosols are omitted. We look for the robust impact across models and volcanoes by combining all the experiments, which helps reveal a signal even if it is weak in the models. The models used in this study simulate realistic levels of warming in the stratosphere, but zonal winds are weaker than the observations. As a consequence, models can produce a pattern similar to the North Atlantic Oscillation in the first winter following the eruption, but the response and impact on surface temperatures are weaker than in observations. Reproducing the pattern, but not the amplitude, may be related to a known model error. There are also impacts in the Pacific and Atlantic Oceans. This work contributes toward improving the interpretation of decadal predictions in the case of a future large tropical volcanic eruption.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Robust Predictive Design of Field Measurements for Evapotranspiration Barriers Using Universal Multiple linear Regression

Surface barriers are normally installed to reduce downward water movement into contaminated zones. Specifically, evapotranspiration (ET) barriers are used to store water and release it, via ET, before it can percolate into an underlying waste zone. To assess the effectiveness of a surface barrier, we used an existing data set, model-simulated data, and a dimensionality reduction approach called universal multiple linear regression (uMLR) to optimize the required number of sensors in a 2-m thick surface barrier. To understand the usefulness of implementing predictive uMLR to accommodate multiple monitoring objectives, we compare several network designs, selected based on down-sampling of existing data, with a recommended sensor design based on model simulations performed without consideration of existing data. We further added consideration of “fuzzy” design, which allows more practical guidelines for field implementation of uMLR. We discovered that uMLR, combined with robust decision-making, provides a simple, flexible, and high-quality network design for monitoring the total water stored in a surface barrier across multiple uncertain conditions.

58 GEOSCIENCES↗
DOE OSTI2023

Assessing the Robustness of Arctic Sea Ice Bi‐Stability in the Presence of Atmospheric Feedbacks

Abstract Arctic sea‐ice loss is influenced by multiple positive feedbacks, sparking concerns of accelerated loss in the coming years or even a tipping point, where a sea‐ice equilibrium disappears at a given CO 2 value and sea ice rapidly evolves to a new steady state. Such a tipping point would imply a bi‐stability of the Arctic climate—where multiple steady‐state Arctic climates are possible at the same CO 2 value. Previous works have sought to establish the existence of bi‐stability using a range of models, from zero‐dimensional sea ice thermodynamic models to fully coupled global climate models, with conflicting results. Here, we present a new model of the Arctic that includes both sea‐ice thermodynamics and key atmospheric feedbacks in a simple framework. We exploit the model's simplicity to identify physical mechanisms that control the timing and extent of sea‐ice bi‐stability, and the abruptness of ice loss. We show that longwave radiation feedbacks can have a strong influence on Arctic surface climate from atmospheric temperature increases alone, even without major contributions from clear‐sky moisture or convective clouds suggested previously. While winter sea‐ice bi‐stability is robust to changes in uncertain model parameters in this study, summer sea ice is more sensitive. Finally, our model indicates that positive feedbacks may modulate the CO 2 threshold of sea‐ice loss and the width of bi‐stability much more strongly than the abruptness of loss. These results lead to a comprehensive understanding of the conditions that favor Arctic sea‐ice bi‐stability, particularly the role of atmospheric feedbacks, in both future and past climates.

Meteorology & Atmospheric Sciences↗
DOE OSTI2026

Examining the Robustness of Weakened Orographic Influence on Precipitation in Downscaled Climate Projections Over the Western US

Assessing local climate change impacts often requires downscaling coarse global climate model (GCM) output to finer resolution. Two main approaches exist: dynamical downscaling using high-resolution regional climate models, and statistical downscaling based on historical relationships between large-scale and local variables. In a recent analysis of five dynamically downscaled simulations over the western United States, Koszuta et al. (2024, https://doi.org/10.1029/2023gl107298) found that warming weakens orographic influence on winter precipitation, damping increases on windward slopes and amplifying them in rain-shadowed regions. Here we show that this effect is robust across seasons and multiple dynamically downscaled ensembles, and is more pronounced at higher model resolutions. However, it is absent in projections from a widely used statistical model (LOCA2), even when trained on high-resolution future simulations (LOCA2-Hybrid). This highlights a key limitation of many statistical downscaling methods: their preservation of parent GCM trends, which usually fail to capture emergent changes in orographic precipitation patterns.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

Informing Robust Functional Relationship Benchmarks: An Evaluation of the Temperature Sensitivity of Ecosystem Respiration Across the Arctic-Boreal Region

During land model development, simulated carbon dynamics are often benchmarked against observational data sets to evaluate model performance. Functional relationship benchmarks are the relationship between a driving variable (e.g., temperature) and a response variable (e.g., ecosystem respiration) and are a promising tool for assessing model performance by evaluating modeled sensitivities to changing environmental conditions. However, observed functional relationships can be influenced by choices made during data collection and throughout the benchmarking process, impacting the inferred skill of land models. To avoid misrepresenting a model's true performance, it is necessary to systematically evaluate best practices when constructing functional relationship benchmarks. We developed a set of guidelines for constructing functional relationship benchmarks, considering the choice of data set, number of daily observations, temporal extent, and temporal resolution across Alaska and Canada over a 20-year period from 2001 to 2020. The temperature sensitivity of ecosystem respiration from observations, evaluated through an apparent Q 10 , is highly variable both spatially and as a result of the data processing approach applied in the benchmark formation. When benchmarking 13 models from the Warming Permafrost Model Intercomparison Project (WrPMIP), the range in inferred model skill is substantially impacted by the choices applied in constructing functional relationship benchmarks. The inferred performance of a given model is most sensitive to the number of daily observations and temporal extent, followed by choice of benchmark data set and temporal averaging. Results from this analysis can guide the development of consistent and robust functional relationships for future model evaluation studies.

Poe, Jeralyn [Northern Arizona University, Flagsta↗
DOE OSTI2015

Robust production of recombinant phosphoproteins using cell-free protein synthesis

Understanding the functional and structural consequences of site-specific protein phosphorylation has remained limited by our inability to produce phosphoproteins at high yields. Here we address this limitation by developing a cell-free protein synthesis (CFPS) platform that employs crude extracts from a genomically recoded strain of Escherichia coli for site-specific, co-translational incorporation of phosphoserine into proteins. We apply this system to the robust production of up to milligram quantities of human MEK1 kinase. Then, we recapitulate a physiological signalling cascade in vitro to evaluate the contributions of site-specific phosphorylation of mono- and doubly phosphorylated forms on MEK1 activity. We discover that only one phosphorylation event is necessary and sufficient for MEK1 activity. Our work sets the stage for using CFPS as a rapid high-throughput technology platform for direct expression of programmable phosphoproteins containing multiple phosphorylated residues. This work will facilitate study of phosphorylation-dependent structure–function relationships, kinase signalling networks and kinase inhibitor drugs.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Micron-gap spacers with ultrahigh thermal resistance and mechanical robustness for direct energy conversion

Abstract In thermionic energy converters, the absolute efficiency can be increased up to 40% if space-charge losses are eliminated by using a sub-10-µm gap between the electrodes. One practical way to achieve such small gaps over large device areas is to use a stiff and thermally insulating spacer between the two electrodes. We report on the design, fabrication and characterization of thin-film alumina-based spacers that provided robust 3–8 μm gaps between planar substrates and had effective thermal conductivities less than those of aerogels. The spacers were fabricated on silicon molds and, after release, could be manually transferred onto any substrate. In large-scale compression testing, they sustained compressive stresses of 0.4–4 MPa without fracture. Experimentally, the thermal conductance was 10–30 mWcm −2 K −1 and, surprisingly, independent of film thickness (100–800 nm) and spacer height. To explain this independence, we developed a model that includes the pressure-dependent conductance of locally distributed asperities and sparse contact points throughout the spacer structure, indicating that only 0.1–0.5% of the spacer-electrode interface was conducting heat. Our spacers show remarkable functionality over multiple length scales, providing insulating micrometer gaps over centimeter areas using nanoscale films. These innovations can be applied to other technologies requiring high thermal resistance in small spaces, such as thermophotovoltaic converters, insulation for spacecraft and cryogenic devices.

42 ENGINEERING↗