Fabrication Artifacts Research Articles

Advances in elastomeric mount concepts for quasi-zero stiffness isolation

Quasi-zero stiffness (QZS) mounts can exploit geometric nonlinearity to minimize stiffness about an operating point, which isolates vibrations from a supported source or receiver. Previous research on elastomeric QZS mounts featured 3D-printed prototypes but did not consider unique material properties and fabrication artifacts that may impact the static and dynamic behavior of the mounts. Additionally, multi-axis properties and their influence on common box-like systems supported by several mounts lack detailed study. To overcome these limitations and improve the practicality of elastomeric QZS mechanisms, this article discusses nonlinear stiffness, hysteresis, and fabrication issues with elastomeric materials in this context. Multimaterial mount designs that improve strength and stability are considered, and their effectiveness for QZS isolation is experimentally evaluated. System-level dynamics are presented for a box-like load supported by QZS mounts. Comparisons between additive and cast materials in the fabrication of QZS mounts are discussed, and the mounts' dynamic stiffness amplification effect is examined for additive and molded materials.

Advances in elastomeric mount concepts for quasi-zero stiffness isolation

Quasi-zero stiffness (QZS) mounts can exploit geometric nonlinearity to minimize stiffness about an operating point which isolates vibrations from a supported source or receiver. Previous research on elastomeric QZS mounts featured 3D printed prototypes but did not consider unique material properties and fabrication artifacts that may impact the static and dynamic behavior of the mounts. Additionally, multi-axis properties and their influence on common, box-like systems supported by several mounts lacks detailed study. To overcome these limitations and improve the practicality of elastomeric QZS mechanisms, this paper discusses nonlinear stiffness, hysteresis, and fabrication issues with elastomeric materials in this context. Multi-material mount designs that improve strength and stability are considered, and their effectiveness for QZS isolation is experimentally evaluated. System-level dynamics are presented for a box-like load supported by QZS mounts. Comparisons between additive and cast materials in the fabrication of QZS mounts are discussed, and the mounts' dynamic stiffness amplification effect is examined for additive and molded materials.

Merging toroidal dipole bound states in the continuum without up-down symmetry in Lieb lattice metasurfaces

Abstract The significance of bound states in the continuum (BICs) lies in their potential for theoretically infinite quality factors. However, their actual quality factors are limited by imperfections in fabrication, which lead to coupling with the radiation continuum. In this study, we present a novel approach to address this issue by introducing a merging BIC regime based on a Lieb lattice. By utilizing this approach, we effectively suppress the out-of-plane scattering loss, thereby enhancing the robustness of the structure against fabrication artifacts. Notably, unlike previous merging systems, our design does not rely on the up-down symmetry of metasurfaces. This characteristic grants more flexibility in applications that involve substrates and superstrates with different optical properties, such as microfluidic devices. Furthermore, we incorporate a lateral band gap mirror into the design to encapsulate the BIC structure. This mirror serves to suppress the in-plane radiation resulting from finite-size effects, leading to a remarkable ten-fold improvement in the quality factor. Consequently, our merged BIC metasurface, enclosed by the Lieb lattice photonic crystal mirror, achieves an exceptionally high-quality factor of 105 while maintaining a small footprint of 26.6 × 26.6 μm. Our findings establish an appealing platform that capitalizes on the topological nature of BICs within compact structures. This platform holds great promise for various applications, including optical trapping, optofluidics, and high-sensitivity biodetection, opening up new possibilities in these fields.

Supercurrent diode effect in thin film Nb tracks

We demonstrate nonreciprocal critical current in 65 nm thick polycrystalline and epitaxial Nb thin films patterned into tracks. The nonreciprocal behavior gives a supercurrent diode effect, where the current passed in one direction is a supercurrent and the other direction is a normal state (resistive) current. We attribute fabrication artifacts to creating the supercurrent diode effect in our tracks. We study the variation of the diode effect with temperature and the magnetic field and find a dependence with the width of the Nb tracks from 2 to 10 μm. For both polycrystalline and epitaxial samples, we find that tracks of width 4 μm provide the largest supercurrent diode efficiency of up to ≈30%, with the effect reducing or disappearing in the widest tracks of 10 μm. We propose a model based on the limiting contributions to the critical current density to explain the track width dependence of the induced supercurrent diode effect. It is anticipated that the supercurrent diode will become a ubiquitous component of the superconducting computer.

Electronic design automation for increased robustness in inkjet-printed electronics

Printed electronics is of great interest for low-cost, large-area fabrication due to fast and scalable processes with low material consumption. However, notable resources are currently required for fine-tuning layout designs and process parameters to prevent unintended fabrication artifacts. This study proposes the use of electronic design automation to mitigate such artifacts by segmenting input layouts and arranging the resulting objects in separate conflict-free layers. To this end, two exemplary conflicts with relevance for inkjet printing are defined. The first addresses heterogeneous structures composed of low- and high-resolution features. The second is concerned with layouts requiring a high feature density. Experimental data is used to derive constraints for layer arrangement. Finally, mixed-integer-linear programming is used to formally model the problem and minimize the total number of layers under the aforementioned constraints. The results of printing test layouts with and without algorithmic treatment are characterized in terms of film morphology, device functionality, and fabrication yield. The data demonstrates a more consistent fabrication outcome and significantly increased yields for optimized fabrication batches compared to non-optimized ones. The final processing of the layouts requires no human intervention and can readily be transferred to a variety of ink-substrate systems.

Dynamic Authentication Protocol Using Self-Powered Timers for Passive Internet of Things

Passive Internet of Things (IoT) like radio frequency identification (RFID) tags can be used to offer a wide range of services, such as object tracking or classification, marking ownership, noting boundaries, and indicating identities. While the communication link between a reader of the tag and the authentication server is generally assumed to be secure, the communication link between the reader and participating tags is mostly vulnerable to malicious acts. Many authentication protocols have been proposed in literature, however, they either are vulnerable to certain types of attacks or require prohibitively a large amount of computational resources to be implemented on a passive tag. In this paper, we present variants of a novel authentication protocol that can overcome the security flaws of previous protocols while being well suited to the computational capability of the tags. At the core of the proposed approach is our recently demonstrated self-powered timing devices that can be used for robust time-keeping and synchronization without the need for any external powering. The outputs of the timers are processed using a single hash function on the tag to produce tokens that continuously change with time, while being synchronized to tokens generated by the authentication server. The proposed protocol also incorporates margins of tolerance that make the authentication process robust to any deviations in the timer responses due to fabrication artifacts.

Fabrication of an Interlocked Antibiotic/Cement-Coated Carbon Fiber Nail for the Treatment of Long Bone Osteomyelitis.

Successful management of intramedullary long bone osteomyelitis remains a challenge for both surgeons and patients. Patients are often immune compromised and have endured multiple surgeries. Treatment principles include antibiotic administration (systemically ± locally), surgical debridement of the infection site, and stabilization. Since their description in 2002, antibiotic-coated nails have become part of the armamentarium for the treatment of osteomyelitis allowing both local elution of antibiotics and stabilization of a debrided long bone. Limitations to their utilization have remained, in part from the technical difficulty of fabrication and magnetic resonance imaging artifacts. We describe a new surgical technique of fabrication that has the advantages of being simple, reproducible, with an end product free of magnetic resonance imaging artifacts.

Fabrication artifacts and parallel loss channels in metamorphic epitaxial aluminum superconducting resonators

Fabrication of coplanar waveguide resonators with internal quality factors near 106 remains challenging. Here, high-purity superconductors are implemented through metamorphic epitaxial aluminum that is grown via molecular beam epitaxy on silicon and sapphire substrates. X-ray diffraction and scanning transmission electron microscopy indicate an abrupt highly ordered interface that results in crystal relaxation within a few monolayers of the substrate interface and no measurable interfacial contamination. Quarter-wave coplanar waveguide resonators are fabricated using optical lithography and measured at temperatures below 100 mK. Post measurement characterization with charge contrast imaging in a scanning electron microscope identifies processing artifacts at the waveguide sidewalls, on the exposed substrate area and on the exposed aluminum surface. Of primary importance are processing induced corrosion defects on aluminum sidewalls, nanoparticle contamination, and photoresist residue that is difficult to remove without affecting the superconductor material. Likely correlations between these artifacts and the measured quality factor are discussed in context of device to device variations in resonator performance.

MR-compatible antibiotic interlocked nail fabrication for the management of long bone infections: first case report of a new technique

Successful management of intramedullary long bone osteomyelitis remains a challenge for both surgeons and patients. Patients are often immune-compromised and have endured multiple surgeries. Treatment principles include antibiotic administration (systemically +/- locally), surgical debridement of the infection site and stabilization. Since their description in 2002, antibiotic coated nails have become part of the armamentarium for the treatment of osteomyelitis allowing both local elution of antibiotics and stabilization of a debrided long bone. Limitations to their utilization have remained, in part from the technical difficulty of fabrication and MRI artifacts. We describe a new surgical technique of fabrication that has the advantages of being simple, reproducible, with an end product free of MRI artifacts.

Submicron-diameter semiconductor pillar microcavities with very high quality factors

Pillar microcavities are subject to two common fabrication artifacts: Bragg mirror corrugation and oxide deposit cladding. In this letter the authors investigate the impact of these features on the quality factor. A quasiperiodic variation of the quality factor as a function of the pillar diameter is experimentally observed and well described by theory. Moreover, observation of quality factors in excess of 1500, close to the theoretical limit, is reported for 600-nm-diameter GaAs micropillars bounded by AlGaAs∕GaAs Bragg mirrors.

Image metrics in the statistical analysis of DNA microarray data.

DNA microarrays represent an important new method for determining the complete expression profile of a cell. In "spotted" microarrays, slides carrying spots of target DNA are hybridized to fluorescently labeled cDNA from experimental and control cells and the arrays are imaged at two or more wavelengths. In this paper, we perform statistical analysis on images of microarrays and show that quantitating the amount of fluorescent DNA bound to microarrays is subject to considerable uncertainty because of large and small-scale intensity fluctuations within spots, nonadditive background, and fabrication artifacts. Pixel-by-pixel analysis of individual spots can be used to estimate these sources of error and establish the precision and accuracy with which gene expression ratios are determined. Simple weighting schemes based on these estimates are effective in improving significantly the quality of microarray data as it accumulates in a multiexperiment database. We propose that error estimates from image-based metrics should be one component in an explicitly probabilistic scheme for the analysis of DNA microarray data.

Microstructural examination of commercial ferritic alloys at 200 dpa

Microstructures and density change measurements are reported for martensitic commercial steels HT-9 and modified 9Cr1Mo (T91) and oxide dispersion strengthened ferritic alloys MA956 and MA957 following irradiation in the FFTF/MOTA at 420°C to 200 dpa. Swelling as determined by density change remains below 2% for all conditions. Microstructures are found to be stable except in recrystallized grains of MA957, which are fabrication artifacts, with only minor swelling in the martensitic steels and α′ precipitation in alloys with 12% or more chromium. These results further demonstrate the high swelling resistance and microstructural stability of the ferritic alloy class.

On the factors affecting strength of portland cement

This paper reports mechanical property measurements for Portland Cement paste free from fabrication artifacts (e.g. bubble-type voids), and compares them to published results both for normal and new high strength cement. Removal of large voids (above 100μm) by vacuum de-airing leads to an increase of ∼ 15% in mean flexural strength and a small decrease in fracture toughness. This increase in flexural strength is predictable from the tied-crack model previously proposed to explain the notch-sensitivity behaviour of hardened cement paste, and for which direct experimental evidence was obtained. It is suggested that factors such as moisture content are at least as important as large voids in controlling mechanical properties. It is concluded that the much increased strength of the new polymer-containing cements must result from improvements to the microstructure other than the simple elimination of voids.