Silicon Core Research Articles

INFLUENCE OF KNOT NUMBER ON HOLDING CAPACITY OF TWO HIGH-STRENGTH SUTURE TAPES: A BIOMECHANICAL ANALYSIS

The number of seven needed knots to provide secure hold of high strength sutures was previously reported. New technologies like tape sutures and sutures with a salt infused silicon core have been developed, potentially reducing the number of needed knots. Study aims: To investigate the influence of (1) throw number and (2) different ambient conditions on knot security in two different high-strength sutures, and (3) to compare their biomechanical competence.Two sutures (SutureTape (FT); n=56 and DynaTape (DT); n=56) were assigned for knot tying. Specimens were exposed to different media during tying, namely air, saline solution, and fat. A monotonic tensile ramp was applied. For each suture and ambient condition, seven specimens with 3 to 7 throws each were tested (n=7), evaluating their slippage and ultimate force to failure. The minimum number of throws preventing suture unraveling was determined in each suture and condition.For each suture type and condition failure occurred via rupturing in all specimens for the following minimum number of throws: FT: dry–6, wet–6, fatty-wet–6; DT: dry–6; wet–4; fatty-wet–5. No significant differences were found comparing ultimate load to rupture of the two groups with minimum number of needed throws in each media. (FT dry-6 vs. DT dry-6; p<0.07); (FT wet-6 vs. DT wet-4; p<0.20); (FT fat-6 vs. DT fat-5; p<0.58). Knot slippage of DT was significantly higher in wet and fatty conditions compared to ST p<0.001 and p<0.004.In fatty-wet conditions DT requires 5 throws to achieve a secure knot. In wet conditions this number can be reduced to 4 throws. FT needs 6 throws to provide a stable knot in all conditions. The biomechanical competence of both sutures in terms of knot slippage and peak force are comparable.

Reduced graphene oxide-encaged submicron-silicon anode interfacially stabilized by Al2O3 nanoparticles for efficient lithium-ion batteries.

Silicon-carbon composites have been recognized as some of the most promising anode candidates for advancing new-generation lithium-ion batteries (LIBs). The development of high-efficiency silicon/graphene anodes through a simple and cost-effective preparation route is significant. Herein, by using micron silicon as raw material, we designed a mesoporous composite of silicon/alumina/reduced graphene oxide (Si/Al2O3/RGO) via a two-step ball milling combined annealing process. Commercial Al2O3 nanoparticles are introduced as an interlayer due to the toughening effect, while RGO nanosheets serve as a conductive and elastic coating to protect active submicron silicon particles during lithium alloying/dealloying reactions. Owing to the rational porous structure and dual protection strategy, the core/shell structured Si/Al2O3/RGO composite is efficient for Li+ storage and demonstrates improved electrical conductivity, accelerated charge transfer and electrolyte diffusion, and especially high structural stability upon charge/discharge cycling. As a consequence, Si/Al2O3/RGO yields a high discharge capacity of 852 mA h g-1 under a current density of 500 mA g-1 even after 200 cycles, exhibiting a high capacity retention of ∼85%. Besides, Si/Al2O3/RGO achieves excellent cycling reversibility and superb high-rate capability with a stable specific capacity of 405 mA h g-1 at 3000 mA g-1. Results demonstrate that the Al2O3 interlayer is synergistic with the indispensable RGO nanosheet shells, affording more buffer space for silicon cores to alleviate the mechanical expansion and thus stabilizing active silicon species during charge/discharge cycles. This work provides an alternative low-cost approach to achieving high-capacity silicon/carbon composites for high-performance LIBs.

Temperature Dependence of Nonlinear Pulse Reshaping Towards Parabolic Shape for a Silicon Core Single Mode Optical Fiber

Temperature Dependence of Nonlinear Pulse Reshaping Towards Parabolic Shape for a Silicon Core Single Mode Optical Fiber

Boosting the anode performance of the porous Si coated with polydopamine and cross-linked with sodium alginate

Silicon-based materials are expected to be the next generation anode for lithium-ion batteries due to their high theoretical specific capacity (4200 mAh g-1) and abundant natural reserves. However, volume expansion (∼300%) and low conductivity issues hinder the further application of silicon-anode materials. Nano-sizing/confinement and the Si@C core-shell techniques are usually employed to depress volume expansion and enhance electrical conductivity of silicon anodes. However, the so-called “island effect” of nanoparticles and the loss of connection between the carbon shell and silicon core can lead to the degradation of electrochemical performance. In this work, nanoporous silicon (pSi) was prepared by means of magnesiothermic reduction of silicon aerogel as a precursor. The pSi is encapsulated by polydopamine (PDA) and then cross-linked by sodium alginate (SA) to form a three-dimensional network structure. It can effectively depress the drastic swelling-shrinking of silicon, avoid the "island effect" of silicon particles, and provide many effective conductive channels. The prepared Si@PDA-SA composite electrode delivers an initial discharge capacity of 3128 mAh g-1 and an initial coulombic efficiency (ICE) of 82.8%. At a current density of 2000 mA g-1, the reversible capacity of 820 mAh g-1 can be retained after 700 cycles. With enhanced mechanical properties and optimal link of the silicon particles, the gradual detachment of silicon particles from the adhesive can be effectively inhibited during long-term cycles. It offers the silicon anode superior cycling stability. Such a facile synthesis process and optimal electrochemical performance have laid a solid foundation for the large-scale application of silicon anode electrodes.

Low-loss operation of silicon-on-insulator integrated components at 2.6-2.7 µm.

Development of mid-infrared photonics is gaining attention, driven by a multitude of sensing applications requiring increasingly compact and cost-effective photonics systems. To this end, low-loss operation of µm-scale silicon-on-insulator photonic integration elements is demonstrated for the 2.6-2.7 µm wavelength region. The platform utilizes the 3 µm thick silicon core layer technology enabling demonstration of low-loss and low birefringence waveguides. Measurements of record low single mode waveguide propagation losses of 0.56 ± 0.09 dB/cm and bend losses <0.08 dB for various miniaturized bend geometries are presented and validated by simulation. Furthermore, a wavelength filter based on echelle grating that allows to select several operating channels within the 2.64-2.7 µm band, with a linewidth of ∼1.56 nm for each channel is presented.

Polarization-insensitive silicon optic switch based on mode manipulated power splitters and phase shifters

A polarization-insensitive thermo-optic switch is proposed and demonstrated on the silicon-on-insulator platform with a 220 nm silicon core layer. The present device is based on the Mach–Zehnder interferometer structure, consisting of polarization-insensitive power splitters and polarization-insensitive phase shifters (PIPSs). The polarization-insensitive power splitter has been realized by employing an adiabatic directional coupler, which utilizes the fast adiabatic mode evolution by introducing cubic Bézier curves on outer contours, providing broadband 3-dB power splitting for TE and TM polarization modes with only 70 µm coupling length. For the novel PIPSs, the ridge waveguide with large aspect ratio, based on the mode hybridness property, could obtain the same power consumption (Pπ) for an optical switch working at TE and TM polarizations. Experimental results indicate that the measured insertion losses are less than 2 dB and the extinction ratios are larger than 15 dB over a 40 nm wavelength band (covering the C-band).

Construction of vacancy-enriched Si@Mn3O4-MnS/C heterostructure toward endurable anode for lithium-ion batteries

A configuring vacancy-enriched Mn oxide/sulfide embedded in amorphous carbon layer with highly concentrated vacancies to encapsulate silicon was tentatively explored to overcome the long-term stabilization issues of silicon active center. Our experimental results demonstrate that the configuration of vacancy-enriched Mn3O4-MnS/carbon hybrid coating layer not only functions as a physical separation layer to prevent silicon from direct contact with electrolytes, but also works as an interesting intermediator to facilitate the structure stabilization and the deep utilization of silicon core center. The surface pseudo-capacitive effect dramatically benefits to the modification of the rate performance of silicon. The synthesized Si@Mn3O4-MnS/C anode material maintains a high reversible capacity of 830 mAh/g after undergoing 200 charge–discharge cycles at 200 mA g−1 current density.

Broadband, tunable wavelength conversion using tapered silicon fibers extending up to 2.4 μm

Wavelength conversion via four-wave mixing holds great promise for the construction of broadband and tunable light sources at wavelengths beyond 2 μm. In this work, we design and fabricate a tapered silicon core optical fiber with a dispersion profile that supports efficient conversion spanning the telecom band up to the edge of the mid-infrared spectral region over an extended propagation length. By pumping with a fiber laser centered around 1.99 μm, a tuning range of 690 nm has been measured, although simulations predict that a bandwidth of up to 1255 nm could be observed if a suitable seed source was available. Conversion efficiencies of ∼−30 dB have been obtained over a bandwidth of 380 nm when using an input pump power of only 6 dBm, with a maximum efficiency of −18 dB achieved when the conversion overlaps the strong Raman gain of the silicon core.

Synthesis of a novel organic-inorganic hindered phenol antioxidant derived from polyhedral oligomeric silsesquioxane and its anti-oxidative behavior in polypropylene

To explore antioxidants with high anti-aging efficiency and admirable anti-extraction ability, a novel organic-inorganic hindered phenol antioxidant (AO-POSS) derived from polyhedral oligomeric silsesquioxane (POSS) was successfully synthesized via a nucleophilic substitution reaction. Chlorinated polyhedral oligomeric silsesquioxane with 8 silicon cores was first synthesized by hydrolysis-polycondensation of (3-chloropropyl)trimethoxysilane and further used for preparing AO-POSS by reacting with the sodium salt of hindered phenolic precursor 3-(3,5-Di‑tert‑butyl‑4-hydroxyphenyl)propionic acid (AO). According to the 29Si-NMR spectra, the T8 cores of Cl-POSS occurred cage-rearrangement under the catalytic effect of propionate anion to produce a thermodynamically stable mixed product, AO-POSS (T8, T10, and T12: 23.8 %, 60.5 %, and 15.7 %). When AO-POSS was incorporated into polypropylene (PP), the oxidation induction time (OIT) of the PP/AO-POSS compound (15.8 min) was slightly longer than that of the PP/1010 compound (13.8 min) at the same molar amounts of hindered phenols. Furthermore, the OIT value of PP/AO-POSS/168 (50.7 min) was obviously higher than that of PP/1010/168 (38.1 min), pointing out the enhanced levels of positive synergism between AO-POSS and secondary antioxidants in inhibiting PP oxidation degradation. Hence, it is apparent that AO-POSS possesses high thermo-oxidative stability and anti-aging efficiency in PP. Notably, even after 48 h of Soxhlet extraction, the OIT value of PP/AO-POSS was retained at 69.5 %, while that of PP/1010 was only 32.2 %, indicating the much better anti-extraction ability of AO-POSS.

When were the First Exocontinents?

Earth’s biosphere was able to increase as continents emerged. I assess when continents could first appear on hypothetical rocky planets of nearby stars. Radiogenic heating of the planetary mantle is evaluated through stellar abundances of iron and silicon (core and mantle proxies) and thorium and potassium (mantle heating proxies). The heat per unit mantle mass is compared to a threshold on Earth after which large-scale continents appeared. Longer delays are inferred for some exoplanets, particularly those with high thorium, but earliest continents could have arisen 2 Gyr before those on Earth, among thin disk stars. In the thick disk, continents could appear 4–5 Gyr pre-Earth. Hence, subsolar-metalicity systems could be an important focus in searching for planets where life could be more advanced than on Earth. At least ∼2 worlds with such old continents are expected to be accessible to future space telescopes, such as Habitable Worlds Observatory.

Evolution of double oxygen–neon white dwarf merger remnant

ABSTRACT Double white dwarf (WD) merger process and their post-merger evolution are important in many fields of astronomy, such as supernovae, gamma-ray bursts, gravitational waves, and so on. The evolutionary outcomes of double ultra-massive WD merger remnants are still a subject of debate, though the general consensus is that the merger remnant will collapse to form a neutron star (NS). In this work, we investigate the evolution of a $2.20\, {\rm M}_{\odot }$ merger remnant stemmed from the coalescence of double $1.10\, {\rm M}_{\odot }$ ONe WDs. We find that the remnant ignites off-centre neon burning at the position near the surface of primary WD soon after the merger, resulting in the stable inwardly propagating oxygen/neon (O/Ne) flame. The final outcomes of the merger remnant are sensitive to the effect of convective boundary mixing. If the mixing cannot stall the O/Ne flame, the flame will reach the centre within 20 yr, leading to the formation of super Chandrasekhar mass silicon core, and its final fate probably be NS through iron-core-collapse supernova. In contrast, if the convective mixing is effective enough to prevent the O/Ne flame from reaching the centre, the merger remnant will undergo electron capture supernova to form an ONeFe WD. Meanwhile, we find that the wind mass loss process may hardly alter the final fate of the remnant due to its fast evolution. Our results imply that the coalescence of double ONe WDs can form short lived giant like object, but the final outcomes (NS or ONeFe WD) are influenced by the uncertain convective mixing in O/Ne flame.

Raman amplification at 2.2 μm in silicon core fibers with prospects for extended mid-infrared source generation

Raman scattering provides a convenient mechanism to generate or amplify light at wavelengths where gain is not otherwise available. When combined with recent advancements in high-power fiber lasers that operate at wavelengths ~2 μm, great opportunities exist for Raman systems that extend operation further into the mid-infrared regime for applications such as gas sensing, spectroscopy, and biomedical analyses. Here, a thulium-doped fiber laser is used to demonstrate Raman emission and amplification from a highly nonlinear silicon core fiber (SCF) platform at wavelengths beyond 2 μm. The SCF has been tapered to obtain a micrometer-sized core diameter (~1.6 μm) over a length of 6 cm, with losses as low as 0.2 dB cm−1. A maximum on-off peak gain of 30.4 dB was obtained using 10 W of peak pump power at 1.99 μm, with simulations indicating that the gain could be increased to up to ~50 dB by extending the SCF length. Simulations also show that by exploiting the large Raman gain and extended mid-infrared transparency of the SCF, cascaded Raman processes could yield tunable systems with practical output powers across the 2–5 μm range.

Synthesis and characterization of a novel thermally stable silane-based host material for blue phosphorescent organic light-emitting diodes

We report a novel thermally stable host material, namely, bis[3-(2-indolo[3,2,1-jk]carbazolyl)phenyl)diphenylsilane (Si-IDCz), for use in blue phosphorescent organic light-emitting diodes (PhOLEDs). Here, Si-IDCz exhibits a high glass transition temperature (Tg) of 151 °C as it contains a thermally stable silane moiety. Additionally, the rigid silicon core within Si-IDCz effectively suppresses molecular interactions, resulting in a wide bandgap and high triplet energy. Here, we used Si-IDCz as the single host for the blue PhOLEDs. The blue PhOLED with the single-host Si-IDCz exhibited an external quantum efficiency (EQE) of over 15%; an EQE of over 11% was maintained at a high luminance of 5000 cd/m2 owing to the high thermal stability of the Si-IDCz. Furthermore, an improved EQE of more than 20% was achieved by introducing a mixed-host system to enhance the photoluminescence quantum yield; the efficiency roll-off was reduced as well.

Thermo-optic VO2-based silicon waveguide mid-infrared router with asymmetric activation thresholds and large bi-stability.

We report a novel four-port optical router that exploits non-linear properties of vanadium dioxide (VO2) phase-change material to achieve asymmetrical power threshold response with power limiting capability. The scope of this study lies within the concept, modeling, and simulation of the device, with practical considerations in mind for future experimental devices. The waveguide structure, designed to operate at the wavelength of 5.0 µm, is composed of a silicon core with air and silicon dioxide forming the cladding layers. Two ring resonators are employed to couple two straight waveguides, thus four individual ports. One of the ring resonators has a 100-nm-thick VO2 layer responsible for non-linear behavior of the device. The router achieves 56.5 and 64.5 dB of power limiting at the forward and reverse operating modes, respectively. Total transmission in the inactivated mode is 75%. Bi-stability and latching behavior are demonstrated and discussed.

Mixing gold and iron in nanoparticles by electrical discharges in liquid: A new approach

The possibility to create homogeneous nanoparticles containing iron and gold by nanosecond-pulsed discharges in liquids, without any laser assistance, is demonstrated. Thanks to a new kind of electrode where elements are coated by PVD on a silicon plate, AuFe nanoparticles, ranging from 10 to 50 nm, are synthesized. Depending on their residence time in the discharge, the structure of the homogeneous nanoparticles evolves to become a core–shell structure, either nested or not. Larger submicrometric particles (from 100 to 500 nm) are specifically formed with the present process by the ejection of liquid droplets from the molten pool created by the discharge on electrode surfaces. These larger particles are produced by solidification of a AuFe shell on a silicon core. This new mechanism can be used to create core–shell particles with a shell containing several, possibly immiscible, elements. Thermal post-treatment performed in situ in a TEM microscope shows the AuFe shell, where Au and Fe separate, turning either into a Janus structure or into a SiFe core facetted by gold pyramids.

Atomic/Molecular Layer-Deposited Laminated Li2O-Lithicone Interfaces Enabling High-Performance Silicon Anodes.

Silicon-based materials are of long-standing interest as the anodes for next-generation lithium-ion batteries, yet their low initial Coulombic efficiency and poor interfacial stability are lethal limitations. In this work, we used atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques to fabricate a lithium-containing laminated Li2O-lithicone hybrid film (∼5 nm) on a silicon electrode. The laminated film provides an additional surface Li source around silicon cores, which can partially reimburse the Li loss during battery cycling. Characterization of interfacial components shows that such a laminated Li2O-lithicone interface undergoes gentle element changes and participates in a hybrid solid electrolyte interphase with Li2CO3, Li2O, LixPOFy, and LiF species. Finite element model analysis and morphology characterization demonstrate that the laminated structure design can help relieve the interfacial stress and thus retain the integrity and reactivity of the silicon composite anode during cycling. Moreover, the lithium-based laminated film leads to a fast Li+ migration kinetics on the surface of the electrode as revealed by the galvanostatic intermittent titration technique and density functional theory calculation. Benefiting from the above merits, a silicon anode with a 91.2% initial Coulombic efficiency, a rate performance of 1460 mA h g-1 at 2 A g-1, and a reversible capacity over 646 mA h g-1 after 850 cycles was achieved. This work exemplifies the advantages of lithium-based hybrid films precisely engineered by ALD/MLD techniques for improving performances of advanced silicon anode batteries and deepens understandings on the mechanism of interfacial stability and reaction kinetics.

Functional Fiber Membranes with Antibacterial Properties for Face Masks

Reusable face masks are an important alternative for minimizing costs of disposable and surgical face masks during pandemics. Often complementary to washing, a prolonged lifetime of face masks relies on the incorporation of self-cleaning materials. The development of self-cleaning face mask materials requires the presence of a durable catalyst to deactivate contaminants and microbes after long-term use without reducing filtration efficiency. Herein, we generate self-cleaning fibers by functionalizing silicone-based (polydimethylsiloxane, PDMS) fibrous membranes with a photocatalyst. Coaxial electrospinning is performed to fabricate fibers with a non-crosslinked silicone core within a supporting shell scaffold, followed by thermal crosslinking and removal of the water-soluble shell. Photocatalytic zinc oxide nanoparticles (ZnO NPs) are immobilized on the PDMS fibers by colloid-electrospinning or post-functionalization procedures. The fibers functionalized with ZnO NPs can degrade a photo-sensitive dye and display antibacterial properties against Gram-positive and Gram-negative bacteria (Escherichia coli and Staphylococcus aureus) due to the generation of reactive oxygen species upon irradiation with UV light. Furthermore, a single layer of functionalized fibrous membrane shows an air permeability in the range of 80–180 L/m2s and 65% filtration efficiency against fine particulate matter with a diameter less than 1.0 µm (PM1.0).Graphical abstract

Toward in-fiber nonlinear silicon photonics

Silicon core fibers (SCFs) offer an exciting opportunity to harness the nonlinear functionality of the semiconductor material within the excellent waveguiding properties of optical fiber systems. Over the past two decades, these fibers have evolved from a research curiosity into established components for use across a wide range of photonic applications. This article provides a comprehensive overview of the evolution of the SCFs, with a focus on the development of the fabrication and post-processing procedures that have helped unlock the nonlinear optical potential of this new technology. As well as reviewing the timeline of advancements in nonlinear performance, a perspective will be provided on the current challenges and future opportunities for in-fiber nonlinear silicon systems.

Enhanced stimulated Brillouin scattering in the unsuspended silicon waveguide assisted with genetic algorithms.

Stimulated Brillouin scattering (SBS), originating from the coupling between optical and acoustic waves, has been widely applied in many fields. Silicon is the most used and important material in micro-electromechanical systems (MEMS) and integrated photonic circuits. However, strong acoustic-optic interaction in silicon requires mechanical release of the silicon core waveguide to avoid acoustic energy leakage into the substrate. This will not only reduce the mechanical stability and thermal conduction, but also increase the difficulties for fabrication and large-area device integration. In this paper, we propose a silicon-aluminium nitride(AlN)-sapphire platform for realizing large SBS gain without suspending the waveguide. AlN is used as a buffer layer to reduce the phonon leakage. This platform can be fabricated via the wafer bonding between silicon and commercial AlN-sapphire wafer. We adopt a full-vectorial model to simulate the SBS gain. Both the material loss and the anchor loss of the silicon are considered. We also apply the genetic algorithm to optimize the waveguide structure. By limiting the maximum etching step number to two, we obtain a simple structure to achieve the SBS gain of 2462 W-1m-1 for forward SBS, which is 8 times larger than the recently reported result in unsuspended silicon waveguide. Our platform can enable Brillouin-related phenomena in centimetre-scale waveguides. Our findings could pave the way toward large-area unreleased opto-mechanics on silicon.

Investigation of Silicon Core-Based Fiber Bragg Grating for Simultaneous Detection of Temperature and Refractive Index.

In this article, we theoretically designed and simulated a silicon core fiber for the simultaneous detection of temperature and refractive index. We first discussed the parameters of the silicon core fiber for near single-mode operation. Second, we designed and simulated a silicon core-based fiber Bragg grating and applied it for simultaneous sensing of temperature and environmental refractive index. The sensitivities for the temperature and refractive index were 80.5 pm/°C and 208.76 dB/RIU, respectively, within a temperature range of 0 to 50 °C and a refractive index range of 1.0 to 1.4. The proposed fiber sensor head can provide a method with simple structure and high sensitivity for various sensing targets.