Submicron Diameter Research Articles

Scalable electrospinning using a desktop, high throughput, self-contained system

Electrospinning is a specialized processing technique for the formation of submicron diameter fibers of polymeric and ceramic materials using an electrostatic field. The process has multiple advantages over other nano- and micro- fiber synthesis methods; however, generally suffers from very low fabrication speeds, making it undesirable for scalability. This work assesses the performance of a needle-less, self-contained, high throughput electrospinning system. It further compares the fiber fabrication rates obtained versus two single needle setups with different collectors: (i) a conventional single needle and flat plate geometry, and (ii) a single needle with a rotating collector geometry. Polyvinylpyrrolidone (PVP) in ethanol was used as the model material. The fabrication rate of the high throughput system “HTES” was measured at about 2.6 g/h and was about 15 times that collected of the flat plate. Comparing it to other systems reported in the literature also proved it to be a viable option for high throughput, lab scale electrospinning.

Intercomparison of WRF-chem aerosol schemes during a dry Saharan dust outbreak in Southern Iberian Peninsula

The Iberian Peninsula (IP), where this study is conducted, has experienced an increase of the frequency and intensity of Saharan aerosol dust outbreaks over the latest decades, which may have an impact on its regional climate. The Weather Research and Forecasting model coupled with chemistry (WRF-chem) has been used worldwide to simulate dust outbreaks and can support the analysis of such potential impacts. However, it includes multiple alternative aerosol parameterization choices that have not been conveniently evaluated in the study region yet. Here, three of the most popular WRF-chem aerosol parameterization schemes, namely, the Goddard Chemistry Aerosol Radiation and Transport (GOCART), the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) and the Modal Aerosol Dynamics Model for Europe (MADE) schemes, are inter-compared during a strong and dry dust outbreak on July 2021 in southern IP. The results show that the three schemes predict qualitatively similar dust intrusion patterns that are consistent with ground observations and have inter-model dust loading differences smaller than 4%. However, their average dust size distributions differ notably. While GOCART is reasonably consistent with observations, MOSAIC underpredicts the amount of dust particles with sub-micron diameters and overpredicts that of large particles and MADE does the opposite. This is found to have a strong detrimental impact on the prediction performance of dust optical properties in MOSAIC and MADE, which is related, at least partially, with issues in the required inter-sectional redistribution of dust parameters during the dust emission and calculation of optical properties. Overall, GOCART generally appears a better choice for strong and dry dust outbreak events in southern IP. It remains to be evaluated during wet dust outbreaks, which is a work underway.

Dexamethasone nanocrystals-embedded hydroxypropyl methylcellulose hydrogel increases cochlear delivery and attenuates hearing loss following intratympanic injection

Herein, dexamethasone (DEX) nanocrystalline suspension (NS)-embedded hydrogel (NS-G) was constructed using a hydroxypropyl methylcellulose (HPMC) polymer to enhance cochlear delivery and attenuate hearing loss following intratympanic (IT) injection. Hydrophobic steroidal nanocrystals were prepared using a bead milling technique and incorporated into a polysaccharide hydrogel. The NS-G system with HPMC (average molecular weight, 86,000 g/mol; 15 mg/mL) was characterized as follows: rod-shaped drug crystalline; particle size <300 nm; and constant complex viscosity ≤1.17 Pa·s. Pulverization of the drug particles into submicron diameters enhanced drug dissolution, while the HPMC matrix increased the residence time in the middle ear cavity, exhibiting a controlled release profile. The IT NS-G system elicited markedly enhanced and prolonged drug delivery (> 9 h) to the cochlear tissue compared with that of DEX sodium phosphate (DEX-SP), a water-soluble prodrug. In mice with kanamycin- and furosemide-induced ototoxicity, NS-G markedly enhanced hearing preservation across all frequencies (8–32 kHz), as revealed by an auditory brainstem response test, compared with both saline and DEX-SP. Moreover, treatment with NS-G showed enhanced anti-inflammatory effects, as evidenced by decreased levels of inflammation-related cytokines. Therefore, the IT administration of DEX NS-loaded HPMC hydrogels is a promising strategy for treating hearing loss.

Elastic Stretch Limit Exceeding 10% for Silicon Wires with Submicron to Micron Diameters

It is significant to modulate the bandgap of crystalline silicon (c‐Si) by applying large strains on it through controlled stretch. However, investigations on the stretchability of c‐Si are still insufficient, especially for samples with feature sizes in the submicron to micron scale. In this work, the large stretchability of silicon wires with submicron to micron diameters (SiMWs) is reported for the first time by using vapor–liquid–solid grown ultralong SiMWs. The diameters of the SiMW specimens range from 400 nm to 1.8 μm. The loading speed for stretching SiMWs is 100 nm s−1. It is found that the SiMWs with micron diameter have a stretch limit over 10%, while the stretch limit for samples with submicron diameter can reach 12%. The results fill the gaps in the knowledge of micron‐scale silicon materials’ stretchability. The average Young's modulus of SiMWs is measured as 115 GPa. Cyclic loading tests indicate that the tensile deformation of SiMWs is elastic and reversible with no plastic deformation observed. In this work, it is shown that large stretch of SiMWs can be achieved without the need of harsh experimental conditions, which will greatly facilitate the study of large strain engineering on c‐Si to modulate their properties and broaden their applications.

Kinetic study of propane ODH on electrospun vanadium oxide-based submicron diameter fiber catalyst

A rigorous kinetic study of the oxidative dehydrogenation (ODH) reaction of propane on a vanadium oxide-based submicron diameter fiber catalyst has been developed. The proposed kinetic model simulates the conversion-selectivity profiles, the surface coverage of the different adsorbed species and the oxidation state of the catalyst for the studied operating conditions of temperature, space–time and inlet partial pressures of propane and oxygen. The activation energy of the rate determining step (RDS), the first hydrogen abstraction from propane, is 104 kJ·mol−1. The model predicts that although the reaction seems to be pseudo-zero order with respect to oxygen in a broad range of conditions, the catalyst may not be fully oxidized during reaction. The accuracy of the model when predicting the oxidation state of the catalyst has been experimentally confirmed by analyzing the catalytic fixed bed after reaction. The reduction degree of the catalyst will depend on its intrinsic chemical nature and reaction conditions, increasing with the space–time and in detriment of the overall reaction rate. Consequently, the propane turnover frequency (TOF) will also depend on the reaction conditions and space–time, even changing along the fixed-bed reactor.

An Automated Setup for the Manufacture of Tapered Optical Fibers with a Submicron Diameter

An Automated Setup for the Manufacture of Tapered Optical Fibers with a Submicron Diameter

CUBOSOME-A Novel Drug Delivery for Anticancer Drugs

Abstract: This literature study will investigate cubosomal preparation in various pharmaceutical compositions. Cubosomal particles are nanostructured liquid crystalline particles with submicron diameters ranging from 10 to 500 nanometers with high encapsulation efficacy. This literature has investigated the anatomy and function of cubosomal units, as well as their formulation, material application, benefit, disadvantage, and preparation technique. Due to their nano-irritancy, cubosomal nanostructures have become a preferred method for treating a range of illnesses.

The Effect of Electrospinning Parameters on the Electrospun Polybutylene Adipate Co-Terephthalate (PBAT) Biodegradable Scaffold

Electrospinning is a cost-effective and versatile technique to fabricate continuous fibers ranging from submicron diameter to nanometer diameter. Polybutylene adipate-co-terephthalate (PBAT) has been investigated as a fibrous scaffold because of its low crystallinity, rapid biodegradability, and excellent mechanical properties, particularly for its high toughness and flexibility. However, the potential of the PBAT fibrous scaffold for medical purposes is still limited. PBAT blends with biocompatible polymers have been developed and investigated for tissue engineering applications. Herein, the preliminary research examines the processability of neat PBAT as a fibrous scaffold by varying several electrospinning processing parameters, such as solution concentration, voltage, flow rate, and tip to collector distance. The aim is to obtain continuous, smooth, and bead-free fibers. The electrospun fibers were examined using a scanning electron microscope (SEM) to determine its diameters. The optimum parameters for obtaining a continuous, bead-free PBAT fibrous scaffold were 20% w/v concentration, 19 kV voltage, 2 mL/h flow rate, and a 15 cm distance.

(Energy Technology Division Walter van Schalkwijk Award in Sustainable Energy Technology Address) Exploring New Electrode Designs with Nanofibers

In recent years, electrospinning has been gaining popularity as a robust and scalable technique for the fabrication of non-woven mats of sub-micron diameter polymer fibers. Although not as well studied, the technique can also be used to prepare particle/polymer fiber networks with high intra- and inter-fiber porosity. Such fibrous mats can be used as porous electrodes in fuel cells and batteries, where a high electrode/electrolyte interfacial area is needed. In this talk, particle/polymer electrospinning will be presented as a platform technique to fabricate a variety of electrode and membrane-electrode-assembly (MEA) products with unique and desirable compositions, architectures, and performance characteristics. Laboratory results will be presented for: (1) hydrogen/air fuel cell cathodes with Pt/C and PGM-free catalysts, (2) Pt/C hydrogen electrodes in a H2/Br2 redox flow battery, and (3) Si anodes for lithium-ion batteries.High particle content fibers containing Pt/C or Pt-alloy catalyst powder and a Nafion®perfluorosulfonic acid binder have shown great promise as electrodes in H2/air fuel cells. During electrospinning, Nafion ionomer migrates to the outer edges of the fiber, effectively creating a core-shell fiber morphology, with a low I/C ratio in the fiber interior. Additionally, the interior of the fiber contains nm-size pores and the outer surface of the Nafion shell exhibits enhanced hydrophobicity, due presumably to an accumulation of the polytetrafluoroethylene backbone chains (-CF2-CF2-) of Nafion. The resulting structure is advantageous in that the majority of catalyst particles are in a low I/C environment, nanopores in the fiber interior trap electro-generated water via capillary condensation, and the hydrophobic surface of the fibers facilitates electrogenerated water removal from the mat during fuel cell operation. The fuel cell power output using fiber mat anodes and cathodes is very high for a low Pt loading (0.10 -0.20 mg/cm2), near or above 1.0 W/cm2 for H2/air feeds in the range of 60-100% relative humidity.1,2 Additionally, the fiber mat cathodes exhibit excellent durability, with minimal power loss after accelerated voltage cycling tests. The hydrophobicity of fibers can be enhanced by adding polyvinylidene fluoride (PVDF) directly to the Nafion binder. Such blended binders in fiber/particle hybrid electrodes extend the operational lifetime of fuel cells with iron-based PGM-free cathode MEAs.As an extension of the fuel cell electrode work, electrospun Pt/C-Nafion nanofiber mat hydrogen electrodes have been made and tested for a H2-Br2 redox flow battery.3 The hydrophobic surface coating of core-shell fibers effectively blocks bromine species from poisoning the hydrogen electrode. In a 6.6 M HBr electrolyte lab-scale redox flow battery, the fiber mat electrodes worked extraordinarily well, with: (i) high power at low Pt loading, e.g., 650 mW/cm2 at 0.70 Vfor a loading of 0.11 mgPt/cm2 (6.4 kW/gPt) and 550 mW/cm2 at 0.65 V for a loading of 0.048 mgPt/cm2 (11.5 kW/gPt), (ii) no loss in power for more than 170 charge/discharge cycles, and (iii) a roundtrip current efficiency of 95%at both 0.2 and 0.3 A/cm2.For Li-ion battery applications, single and dual fiber anode mats have been prepared and evaluated, where the fibers contain a polymer binder (e.g., polyacrylic acid, polyamidimide, or polyvinylidene fluoride), Si nanoparticles as the electrochemically active material, and carbon powder as an electron conductor.4 Here, the gravimetric and areal capacities of the fiber anode are considerably higher than those of a conventional carbon particle anode. Inter-fiber voids allow for volume changes in Si during lithiation/delithiation, thus minimizing capacity fade during charge/discharge cycling (up to 600 cycles).AcknowledgmentsThis work was funded by the U.S. Department of Energy, Contract No. DE-EE0007653 from the Fuel Cell Technologies Office, through the Fuel Cell Performance and Durability Consortium (Fuel Cells Program Manager: Dimitrios Papageoropoulos) and Contract No. DE-EE0007215 from the Vehicle Technology Office.

Lighting Up at High Potential: Effects of Voltage and Emitter Size in Nanoelectrospray Ionization.

Effects of electrospray voltage on cluster size and abundance formed from aqueous CsI were investigated with emitter tip diameters between 260 ± 7 nm and 2.45 ± 0.30 μm. Cluster size increases with increasing voltage, increasing solution concentration and increasing emitter diameter consistent with formation of larger initial droplet sizes. For emitters with tip diameters above ∼1 μm, varying the voltage either up or down leads to reproducible voltage-dependent extents of cluster formation. In contrast, higher voltages with submicron diameter emitters can lead to only Cs+ and Cs(H2O)+ and no clusters. This change in ion formation reproducibly occurs at spray potentials >1.3 kV for 260 nm emitters and appears to be induced by a corona discharge and material build-up at the emitter tip. Under conditions where abundant Cs+ is observed and no clusters are formed, ions such as K+ and Cu1+ are also observed but ions with more negative solvation energies, such as Ba2+, are not. Similarly, ions from bradykinin and ubiquitin are observed predischarge but not post discharge. Ions with more positive solvation energies can desorb directly from the air-water interface that is created at the tip of these emitters, whereas ions with more negative solvation energies as well as peptide and protein ions do not. These results indicate that ion desorption directly from solution can occur, and similar experiments with even smaller emitters may lead to new insights into ion formation in electrospray ionization.

A plant growth chamber system equipped with aerosol generators for studying aerosol-vegetation interactions

Understanding aerosol-vegetation interactions is vital in ecosystems. However, the interactions remain elusive partly due to the lack of suitable plant growth chamber systems. Particularly, deposition of submicron particles on leaf surfaces is challenging due to its low deposition velocities compared to larger particles. In this work, we present a plant-growth chamber that was used to study the effect of submicron black carbon (BC) particles on the growth and photosynthesis of plants. The chamber system simultaneously enables the growth of multiple plants in pots and the deposition of submicron particles onto them. Two spraying methods assisted by ultrasonic and electrostatic forces were employed as aerosol generators to realize the particle deposition. The flow regime inside the chamber was numerically calculated to predict the transportation of aerosol particles, suggesting the optimal operating conditions of the chamber. The gas-phase particle size distribution measurements showed that generated BC particles were suspended in submicron diameter ranges. The aerosol generators were examined in the chamber using three conductor and insulator substrates as a model of plant leaves. Microscope observations and spectroscopic analysis ascertained that submicron BC particles generated from our generators were deposited on all substrate surfaces. Using the developed chamber system, systematic studies can be performed to advance the fundamental understanding of aerosol-vegetation interactions.

On the detection of nanoparticle cloud migration by a resonant photonic surface signal towards sedimentation velocity measurements

Migration and sedimentation of solid particles in a liquid are physical phenomena involving accumulation of soft matter or decantation of fragmented matter. A thorough understanding together with relevant measurements are prerequisites regarding many fields, including medicine, galenic pharmacology, food processing, and the cosmetics industry. In this paper, we investigate the feasibility of monitoring and detecting the migration of a nanoparticle cloud with a resonant light probe. For this purpose, hybrid silicon/silica/UV210 organic integrated photonic racetrack resonators were patterned by thin film processes to be used as sensors measuring the outcome of the impact of a cloud of nanoparticles, the dynamic migration plus sedimentation phenomenon of the nanoparticle cloud in water. A broadband superluminescent diode has been used for the excitation. Then, the spectral characteristics of the resonant guided modes have been analyzed, considering the observed changes while tracking the free spectral range of the transduced comb spectra as a function of time. The way to operate can be summarized as follows: Solutions based on spherical silica nanoparticles of fixed size are prepared and subjected to rheological measurements to obtain their respective viscosities. Next, a millimeter tank filled with water is conveniently placed on the active surface of the sensing chip, prior to the addition of one of the previously mentioned solutions. The series of spectra are acquired during the whole migration sequence and the transduced optical signal is then directly processed and treated by a specific code operated in real time by way of Lagrange interpolation polynomials. Collected data are then compared to a simple theoretical model describing the sedimentation of a spherical particle in water (Stokes' law). Eventually, the implementation of the device in a characterization platform and the development of a specific protocol allows a global treatment, whose description is followed by discussions on measurements and data. Consequently, after the impact of the drop containing the nanoparticles, the monitoring of a first phase regarding their fast cloud migration into the global study volume (with flow of matter plus vortex) eventually followed by their slow sedimentation, can be detected using such a resonant light probe. The overall duration of the first phase associated with sedimentation velocities is in the order of a few tens of µm/min for particles with submicron diameters (several hundreds of nanometers); a first attempt of comparison of this first phase with the results of the classic Stokes model would give a convergence of the values reaching between 9 and 19% for the sedimentation rates.

Diblock Copolymer Stabilized Liquid Metal Nanoparticles: Particle Settling Behavior and Application to 3D Printing.

Eutectic gallium indium (EGaIn) is a liquid metal with promising applications due to its favorable thermal and electrical conductivity, low viscosity, and metallic nature. For applications, including imaging, catalysis, and nanomedicine, stable EGaIn particles with submicron diameters are required. However, the low viscosity and high density of EGaIn have typically precluded the formation of stable submicron particles due to rapid EGaIn droplet coalescence. In this work, we show that poly(acrylic acid)-block-poly(N,N'-dimethylacrylamide) copolymers are able to effectively stabilize EGaIn nanodroplets formed upon ultrasonication, where the poly(acrylic acid) block anchors the polymer to the EGaIn surface and the poly(N,N'-dimethylacrylamide) block provides colloidal stability to the particles in solution. Although the high density of EGaIn causes rapid particle settling, the behavior is predictable, which allows the average particle size to be controlled through centrifugation. We demonstrate that stable EGaIn particles with sizes on the order of 50-100 nm and narrow particle size distributions can be easily obtained using this method and further used in photopolymer resins to prepare 3D printed EGaIn-polymer hybrid materials. The predictable sizes and high stability of these EGaIn nanoparticles should allow further applications in soft-electronics, nanomedicine, catalysis, and other nanotechnology.

Magnetoresponsive Artificial Cilia Self-Assembled with Magnetic Micro/Nanoparticles.

Biological cilia have exquisitely organized dynamic ultrafine structures with submicron diameters and exceptional aspect ratios, which are self-assembled with ciliary proteins. However, the construction of artificial cilia with size and dynamic functions comparable to biological cilia remains highly challenging. Here, we propose a self-assembly technique that generates magnetoresponsive artificial cilia with a highly ordered 3D structural arrangement using vapor-phase magnetic particles of varying sizes and shapes. We demonstrate that both monodispersed Fe3O4 nanoparticles and Fe microparticles can be assembled layer-by-layer vertically in patterned magnetic fields, generating both "nanoscale" or "microscale" artificial cilia, respectively. The resulting cilia display several structural features, such as diameters of single particle resolution, controllable diameters and lengths spanning from nanometers to micrometers, and accurate positioning. We further demonstrate that both the magnetic nanocilia and microcilia can dynamically and immediately actuate in response to modulated magnetic fields while providing different stroke ranges and actuation torques. Our strategy provides new possibilities for constructing artificial nano- and microcilia with controlled 3D morphology and dynamic field responsiveness using magnetic particles of varied sizes and shapes.

Thermooptical PDMS-Single-Layer Graphene Axicon-like Device for Tunable Submicron Long Focus Beams.

Submicron long focusing range beams are gaining attention due to their potential applications, such as in optical manipulation, high-resolution lithography and microscopy. Here, we report on the theoretical and experimental characterization of an elastomeric polydimethylsiloxane/single layer graphene (PDMS/SLG) axicon-like tunable device, able to generate diffraction-resistant submicrometric spots in a pump and probe configuration. The working principle is based on the phase change of an input Gaussian beam induced in the elastomer via the thermo-optical effect, while the heating power is produced by the optical absorption of the SLG. The phase-modified beam is transformed by an objective into a long focus with submicron diameter. Our foci reach an experimental full width at half maximum (FWHM) spot diameter of 0.59 μm at the wavelength of 405 nm, with the FWHM length of the focal line greater than 90 μm. Moreover, the length of the focal line and the diameter of the focus can be easily tuned by varying the pump power. The proposed thermo-optical device can thus be useful for the simple and cheap improvement of the spatial resolution on long focus lines.

Instructive electroactive electrospun silk fibroin-based biomaterials for peripheral nerve tissue engineering.

Aligned sub-micron fibres are an outstanding surface for orienting and promoting neurite outgrowth; therefore, attractive features to include in peripheral nerve tissue scaffolds. A new generation of peripheral nerve tissue scaffolds is under development incorporating electroactive materials and electrical regimes as instructive cues in order to facilitate fully functional regeneration. Herein, electroactive fibres composed of silk fibroin (SF) and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) were developed as a novel peripheral nerve tissue scaffold. Mats of SF with sub-micron fibre diameters of 190±50nm were fabricated by double layer electrospinning with thicknesses of ∼100μm (∼70-80μm random fibres and ∼20-30μm aligned fibres). Electrospun SF mats were modified with interpenetrating polymer networks (IPN) of PEDOT:PSS in various ratios of PSS/EDOT (α) and the polymerisation was assessed by hard X-ray photoelectron spectroscopy (HAXPES). The mechanical properties of electrospun SF and IPNs mats were characterised in the wet state tensile and the electrical properties were examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The cytotoxicity and biocompatibility of the optimal IPNs (α=2.3 and 3.3) mats were ascertained via the growth and neurite extension of mouse neuroblastoma x rat glioma hybrid cells (NG108-15) for 7days. The longest neurite outgrowth of 300μm was observed in the parallel direction of fibre alignment on laminin-coated electrospun SF and IPN (α=2.3) mats which is the material with the lowest electron transfer resistance (Ret, ca. 330Ω). These electrically conductive composites with aligned sub-micron fibres exhibit promise for axon guidance and also have the potential to be combined with electrical stimulation treatment as a further step for the effective regeneration of nerves.

How to design, develop and build a fully-integrated melt electrowriting 3D printer

Melt electrowriting (MEW) is a high resolution material extrusion based additive manufacturing process with the unique capability to produce micron to sub-micron diameter fibres and control their deposition in three dimensions. Here, we detail the design, development and build of a custom MEW printer which has full integration between all core components. We detail the design and build of the motion system, print head (including heaters, extrusion system and high voltage power supply) and safety systems, and explain how these are integrated via a central control unit to provide pre-programmed dynamic control over printing variables allowing the fabrication of a range of advanced material designs with applications in the fields of tissue engineering, regenerative medicine and beyond. We discuss the various approaches which may be used for each system within a custom MEW printer, providing an insight into how it may be designed depending on the specific requirements of the end user. Finally, we demonstrate the capabilities of this printer by producing tissue engineering scaffolds with various architectures. This work aims to make MEW technology more accessible by both informing others interested in developing similar custom devices, and additionally, by providing an insight into the inner workings of MEW technology for practitioners in the field.

Broadband ultrasound sensing based on fused dual-core chalcogenide-PMMA microfibers.

High-frequency ultrasound sensors are essential for high-resolution medical ultrasonic imaging and industrial ultrasonic non-destructive monitoring. In this paper, we propose highly sensitive broadband ultrasound sensors based on fused dual-core chalcogenide-polymethyl methacrylate (As2Se3-PMMA) microfibers. We demonstrate that ultrasound response is determined by the differential slope of transmission spectra in the dual-core microfiber, which is verified by detecting the acoustic response in various microfibers of different tapering parameters. A broadband ultrasound frequency range with a high signal-to-noise ratio (SNR) is achieved in the fused dual-core microfiber (DCM) with a sub-micron core diameter and a close core separation due to the large spectral slope at the quadrature points of the transmission spectrum. In addition, we experimentally demonstrate the sensing of ultrasound waves propagating with and without an aluminum plate in the DCM sensor. An ultrasound sensor with a broadband frequency range from 20 kHz to 80 MHz and an average SNR of 31 dB is achieved in a compact fused dual-core As2Se3-PMMA microfiber when it is directly placed on a piezoelectric transducer (PZT).

Electrospun composites nanofibers from cellulose acetate/carbon black as efficient adsorbents for heavy and light machine oil from aquatic environment

The feasibility of preparing cellulose acetate/carbon black (CA/CB) composite nanofiber in one step through electrospinning process and investigating its potential oil absorbability and application for machine oil removal from aquatic environment was reported. Different CA/CB composite nanofibers were fabricated by electrospinning of cellulose acetate (CA) solution containing different loads of 0.7, 1.5, and 2.2% CB relative to the weight of CA and labeled as CA/CB0.7, CA/CB1.5, and CA/CB2.2. The scanning electron microscope (SEM) images showed continuous and smooth fiber with submicron diameter ranging from 400–900 nm with good adhering of CB into CA nanofiber. Furthermore, the CA/CB composite nanofibers exhibited high surface area compared with CA nanofiber, which reached 3.057, 2.8718 and 8.244 m2/g for CA/CB0.7, CA/CB1.5 and CA/CB2.2, respectively. Oil adsorption tests were performed with heavy and light machine oils. The CA/CB composite nanofibers showed higher affinity for oil removal from an aqueous solution than pure CA nanofiber. The CA/CB1.5 composite nanofiber has an exceptional performance for the adsorption of both oils, and the maximum oil adsorbed reached 10.6 and 18.3 g/g for light and heavy machine oils, respectively. The kinetic of machine oils adsorption was fitted well by the pseudo-second-order model. Besides, CA/CB composite nanofiber exposed good adsorption properties and respectable reusability after regeneration for four consecutive cycles. The results advocate the excellent potential of as-fabricated CA/CB composite nanofiber as a promising reusable oil adsorbent for oil spill cleanup applications.

Aledia Touts MicroLED Chip Progress

FRENCH STARTUP FIRM ALEDIA SAYS IT HAS MANUFACtured the first microLED chips using 300-millimeter (mm), or 12-in., silicon wafers. This development could pave the way for more widespread use of microLED technology in smartphones and televisions by leveraging established silicon foundry technology. Traditional LED chips have been produced using 100- and 150-mm (4- and 6-in.) sapphire wafers, upon which flat layers of gallium-nitride (GaN) crystal are deposited. Aledia, which was spun out of the French government-backed research institute CEA-Leti [Laboratoire d'électronique des technologies de l'information] in Grenoble in 2012, has spent the past eight years developing microLED technology for large-area silicon such as 200-mm (8-in.) silicon wafers. It recently used CEA-Leti's pilot lines to make the leap to 300-mm (12-in.) wafers. Aledia says its 3D nanowire technology grows GaN nanowires (GaN crystals of submicron diameter) on top of large-area silicon. According to the company, this doesn't create the stresses seen with the traditional flat-layer approach, as the wafer size is increased. That means its technology could be used to mass-produce microLEDs with the same 200- and 300-mm wafers used by high-yield silicon foundries today to make smartphone and computer processing chips. This also yields cost-effective integration with smaller-node electronics in the process. Volume chip manufacturing is essential for microLED's long-term success, where each pixel in the display is created by a microscopic LED. “We believe producing microLEDs on large-area 300-mm silicon wafers is a world's first, and opens this technology to huge potential-volume-manufacturing capabilities,” Aledia CEO and cofounder Giorgio Anania says in a press release. “The larger size allows 60 to 100 smartphone displays to be made on a single 300-mm wafer, versus approximately four-to-six using the present LED industry-standard, 4-in. sapphire substrate. Thanks to Aledia's unique nanowire LED technology [3D LED], this can be done with commercially available processes and equipment, since it uses standard-thickness [780 micrometer, or μm] silicon wafers.” Aledia has attracted big investors, including Intel Capital, and in 2019 it reached a process-development partnership with Israeli silicon foundry TowerJazz to commercialize its technology. Last fall, it raised $97 million for building its own microLED plant in Grenoble, which it aims to have operational by mid-2022. Aledia is certainly in a strong financial position, but may still be years away from mass-producing microLEDs on 12-in. wafers, says Yole Développement Senior Industry Analyst Eric Virey. He notes the company's development with TowerJazz to date has been confined to 8-in.-wafers and that Aledia worked with CEA-Leti researchers and used the institute's pilot line for the 12-in.-project, which he describes as being more in the research and development stage. microLED Chip WireLED on 300 mm (12 in.) silicon wafer. Source: Aledia However, one of the biggest roadblocks for microLED is cost, says Virey, and one way to address that is to reduce the LED chip's cost. So even moving to 8-in.-silicon production over smaller-format sapphire wafers would have a tangible benefit. “This opens the door to a vast amount of battle-tested 8-in. [complementary metal-oxide semiconductor] tools and CMOS fabs,” he says. “There are a lot of tools developed, more than anything for LED, and there are a lot of used tools for the grab. It would be a brave new world for microLED to get into the world of 8-in. silicon.” Overall, Virey forecasts a slow rollout for microLEDs in TV displays. Samsung has introduced a commercial 110-in. TV, but with a price tag of around $150,000, it's far from a mainstream consumer product. He says that if development goes well, we might see microLED TVs in the same price range as high-end OLED TVs in five or six years. “The goal of the industry for TV is they need to cut costs by a factor of 10 to 20,” says Virey. “There is a credible path to get there, but nobody is saying it's an easy path, and right now OLED and the other technologies are moving targets.” However, microLED looks more feasible for smaller displays. Virey notes that in 2021, Vuzix is commercializing the first augmented reality (AR) glasses that will use microLED, where its brightness is a big advantage. He expects Apple to start making its own microLED displays for the Apple Watch in late 2022, with commercial introduction probably coming in 2023. “They're only now in the process of building a real pilot line, and a lot will depend on the pilot line,” says Virey. “But that would be a serious disruption for the industry, if [Apple] would start making their own displays.” —By Glen Dickson