31 research outputs found
Ultra-Stretchable Interconnects for High-Density Stretchable Electronics
The exciting field of stretchable electronics (SE) promises numerous novel
applications, particularly in-body and medical diagnostics devices. However,
future advanced SE miniature devices will require high-density, extremely
stretchable interconnects with micron-scale footprints, which calls for proven
standardized (complementary metal-oxide semiconductor (CMOS)-type) process
recipes using bulk integrated circuit (IC) microfabrication tools and
fine-pitch photolithography patterning. Here, we address this combined
challenge of microfabrication with extreme stretchability for high-density SE
devices by introducing CMOS-enabled, free-standing, miniaturized interconnect
structures that fully exploit their 3D kinematic freedom through an interplay
of buckling, torsion, and bending to maximize stretchability. Integration with
standard CMOS-type batch processing is assured by utilizing the Flex-to-Rigid
(F2R) post-processing technology to make the back-end-of-line interconnect
structures free-standing, thus enabling the routine microfabrication of
highly-stretchable interconnects. The performance and reproducibility of these
free-standing structures is promising: an elastic stretch beyond 2000% and
ultimate (plastic) stretch beyond 3000%, with 10
million cycles at 1000% stretch with <1% resistance change. This generic
technology provides a new route to exciting highly-stretchable miniature
devices.Comment: 13 pages, 5 figure, journal publicatio
An adaptive wavelet-based collocation method for solving multiscale problems in continuum mechanics
Computational multiscale methods are highly sophisticated numerical approaches to predict the constitutive response of heterogeneous materials from their underlying microstructures. However, the quality of the prediction intrinsically relies on an accurate representation of the microscale morphology and its individual constituents, which makes these formulations computationally demanding. Against this background, the applicability of an adaptive wavelet-based collocation approach is studied in this contribution. It is shown that the HillâMandel energy equivalence condition can naturally be accounted for in the wavelet basis, (discrete) wavelet-based scale-bridging relations are derived, and a wavelet-based mapping algorithm for internal variables is proposed. The characteristic properties of the formulation are then discussed by an in-depth analysis of elementary one-dimensional problems in multiscale mechanics. In particular, the microscale fields and their macroscopic analogues are studied for microstructures that feature material interfaces and material interphases. Analytical solutions are provided to assess the accuracy of the simulation results
Multilayered Inclusions in Locally Resonant Metamaterials: Two-Dimensional Versus Three-Dimensional Modeling
Locally resonant metamaterials (LRMs) controlling low-frequency waves due to resonant scattering are usually characterized by narrow band gaps (BGs) and a poor wave filtering performance. To remedy this shortcoming, multiresonant metamaterial structures with closely located BGs have been proposed and widely studied. However, the analysis is generally limited to two-dimensional (2D) structures neglecting the finite height of any real resonator. The aim of this paper is the comparison of the wave dispersion for two-and threedimensional (3D) metamaterial models and evaluation of the applicability ranges of 2D results. Numerical study reveals that dual-resonant structures with cylindrical inclusions possess only a single (compared to two in the 2D case) BG for certain height-to-width ratios. In contrast, the wave dispersion in metamaterials with multiple spherical resonators can be accurately evaluated using a 2D approximation, enabling a significant simplification of resource-consuming 3D models
Immunogenicity of an additional mRNA-1273 SARS-CoV-2 vaccination in people with HIV with hyporesponse after primary vaccination
Background:The COVIH study is a prospective coronavirus disease 2019 (COVID-19) vaccination study in 1154 people with HIV (PWH), of whom 14% showed reduced antibody levels after primary vaccination. We evaluated whether an additional vaccination boosts immune responses in these hyporesponders. Methods: The primary end point was the increase in antibodies 28 days after additional mRNA-1273 vaccination. Secondary end points included neutralizing antibodies, S-specific T-cell and B-cell responses, and reactogenicity. Results:Of the 66 participants, 40 previously received 2 doses ChAdOx1-S, 22 received 2 doses BNT162b2, and 4 received a single dose Ad26.COV2.S. The median age was 63 years (interquartile range [IQR], 60â66), 86% were male, and median CD4 + T-cell count was 650/ÎŒL (IQR, 423â941). The mean S1-specific antibody level increased from 35 binding antibody units (BAU)/ mL (95% confidence interval [CI], 24â46) to 4317 BAU/mL (95% CI, 3275â5360) (P < .0001). Of all participants, 97% showed an adequate response and the 45 antibody-negative participants all seroconverted. A significant increase in the proportion of PWH with ancestral S-specific CD4 + T cells (P = .04) and S-specific B cells (P = .02) was observed. Conclusions:An additional mRNA-1273 vaccination induced a robust serological response in 97% of PWH with a hyporesponse after primary vaccination.</p
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
Preface to Special Issue onMultiscale Computational Homogenization: From Microstructure to Properties
On the validity regime of the bulge equations
International audienceThe plane strain bulge test technique is a powerful and acknowledged technique for characterizing the mechanical behavior of thin films. In a bulge test analysis, the stress and strain are derived from the measured quantities using analytical approximations of the deformed geometry (bulge equations). To improve the bulge test, the systematic error introduced by these approximations is evaluated and quantified by scrutinizing the method on a finite element model of the bulge test, used as an idealized experiment
Sampling point selection for energy estimation in the quasicontinuum method
The quasicontinuum (QC) method reduces computational costs of atomistic calculations by using interpolation between a small number of so-called repatoms to represent the displacements of the complete lattice and by selecting a small number of sampling atoms to estimate the total potential energy of the interpolated problem. In this contribution two new sampling point selections are introduced for the QC method. The first selection determines the total potential energy of the lattice exactly in correspondence with the interpolation. Since no error due to summation occurs, the fully resolved regions around lattice defects can remain small. However, in this case many sampling atoms must be used. Therefore a second sampling point selection is derived from the first selection that uses only one sampling atom to represent all atoms within interpolation together with the repatoms. This ensures that the exact lattice model is recovered in the fully resolved regions while a smooth transition is achieved towards coarse regions in which the method becomes very close to the local QC method