Nano-sized Structures Research Articles

Hybrid Nanofibrous Membrane with Durable Electret for Anti-Wetting Air Filtration.

Electrospun fibrous materials with fine fibers and small pores are fundamental for particulate matter (PM) filtration, addressing its harmful environmental and health impacts. However, the existing electrospun fibers are still limited to their sub-micron diameters and unstable surface electrostatic effect, leading to deteriorated filtration performance after prolonged storage or wetting. Herein, the study creates nanofibrous membranes with long-time stable electrostatics by electret-enhanced electrospinning. The phase separation and polarization of the charged jet are manipulated to achieve rapid stretch and strong electret. The obtained membrane exhibits nanosized structures with fiber diameters of ≈220 nm, pore size <1 µm, as well as robust surface potential of 0.4 kV. By virtue of the synergistic effects of sieving and adsorption, the nanofibrous membrane showed a remarkable PM0.3 filtration efficiency of 96.6% and pressure drop of 140 Pa, even reaching the N90 standard after five wetting cycles. The design of such durable membranes will offer a new sight in the functional filtration materials.

Dual-Task Optimization Method for Inverse Design of RGB Micro-LED Light Collimator

Abstract: Miniaturized pixel sizes in near-eye digital displays lead to pixel emission patterns with large divergence angles, necessitating efficient beam collimation solutions to improve the light coupling efficiency. Traditional beam collimation optics, such as lenses and cavities, are wavelength-sensitive and cannot simultaneously collimate red (R), green (G), and blue (B) light. In this work, we employed inverse design optimization and finite-difference time-domain (FDTD) simulation techniques to design a collimator comprised of nano-sized photonic structures. To alleviate the challenges of the spatial incoherence nature of micro-LED emission light, we developed a strategy called dual-task optimization. Specifically, the method models light collimation as a dual task of color routing. By optimizing a color router, which routes incident light within a small angular range to different locations based on its spectrum, we simultaneously obtained a beam collimator, which can restrict the output of the light emitted from the routing destination with a small divergence angle. We further evaluated the collimation performance for spatially incoherent RGB micro-LED light in an FDTD using a multiple-dipole simulation method, and the simulation results demonstrate that our designed collimator can increase the light coupling efficiency from approximately 30% to 60% within a divergence angle of ±20° for all R/G/B light under the spatially incoherent emission.

Extracellular vesicles-a new player in the development of urinary bladder cancer.

Bladder cancer was the 10th most commonly diagnosed cancer worldwide in 2020. Extracellular vesicles (EVs) are nano-sized membranous structures secreted by all types of cells into the extracellular space. EVs can transport proteins, lipids, or nucleic acids to specific target cells. What brings more attention and potential implications is the fact that cancer cells secrete more EVs than non-malignant cells. EVs are widely studied for their role in cancer development. This publication summarizes the impact of EVs secreted by urinary bladder cancer cells on urinary bladder cancer development and metastasis. EVs isolated from urinary bladder cancer cells affect other lower-grade cancer cells or normal cells by inducing different metabolic pathways (transforming growth factor β/Smads pathway; phosphoinositide 3-kinase/Akt pathway) that promote epithelial-mesenchymal transition. The cargo carried by EVs can also induce angiogenesis, another critical element in the development of bladder cancer, and modulate the immune system response in a tumor-beneficial manner. In summary, the transfer of substances produced by tumor cells via EVs to the environment influences many stages of tumor progression. An in-depth understanding of the role EVs play in the development of urinary bladder cancer is crucial for the development of future anticancer therapies.

Modification of blend reverse osmosis membranes using ZrO2 for desalination process purposes

Desalination of water is a crucial step in the process of obtaining potable water. One of the main challenges for the researchers is its efficient application and affordable preparation. It was planned to prepare the flat sheet membranes using cellulose acetate as a base polymer, and polyvinyl alcohol (PVA) as an additive with dosing of (0.1, 0.3, 0.5, and 0.7 wt%) from zirconium oxide (ZrO2) nanoparticle. SEM, TEM, and XRD analyses were used to characterize the generated ZrO2 nanoparticle in order to confirm its nano-size and crystal structure. The surface morphologies and existence of the dense layer, which is the typical property of the RO membrane capable of salt separation, were identified on the manufactured RO membranes by SEM. Membranes prepared by embedding 0.5 wt%ZrO2 with PVA/CA proved efficient as RO membranes using 2000 ppm NaCl and exhibited high salt rejection of 97% and water permeability of 12.5 LMH. Also, there is a decrease in the NaCl removal tendency was observed with the excessive dosages of ZrO2 with 0.7 wt%, which was due to the concentration polarization, which blocks the pores on the surfaces of the membranes. The antifouling behavior of the prepared membranes was tested using bovine serum albumin (BSA), the results indicate the low irreversible resistance, total fouling resistance, and high flux recovery ratio compared to the neat membrane. The prepared membranes have a stable salt rejection and water productivity even after demonstrating with chlorine (25–100 mg l−1 of NaOCl for 120 min).

Enhancing the Cycle Life of Silicon Microparticle Anodes for High-Energy Density Lithium-Ion Batteries through a Reinforced Conductive Matrix

Silicon (Si) is increasingly regarded as a promising candidate for anode materials in lithium-ion batteries (LIBs) owing to its exceptional theoretical specific capacity and abundant material resources. However, widespread commercial adoption faces hurdles due to inherent challenges such as significant volume expansion and the uncontrolled growth of the solid-electrolyte interphase (SEI) during cycling. To address these obstacles, numerous strategies have been proposed, including the fabrication of nano-sized silicon structures to enhance structural stability and long cyclability. Nonetheless, reducing silicon to the nanoscale diminishes the initial coulombic efficiency (ICE) and tap density of Si nanomaterials, thereby hindering the commercialization of Si anodes. Si microparticles (SiMPs) exhibit higher ICE and volumetric capacity compared to Si nanoparticles (SiNPs), making them better suited to meet the requirements of high energy density. However, their larger particle size also increases susceptibility to pulverization during cycling. Despite numerous efforts to enhance the performance of SiMP anodes, the conventional anode structure typically comprises active materials, conductive additives, and a polymeric binder. This traditional structure is prone to damage caused by the substantial volume expansion and shrinkage of SiMPs, resulting in the isolation of electrical network. To overcome these limitations, we propose a novel electrode architecture consisting of active materials, reinforcing materials, and a conductive matrix. The reinforcing materials act as a bridge between the active materials and the conductive matrix, enhancing the electrode's elasticity. The conductive matrix integrates the functionalities of both binder and conductive additive, eliminating the need for nonconductive binders. Consequently, the issue of electrical connectivity in the SiMP electrode during repeated cycling is addressed. The conductive matrix is synthesized using a simple method involving the cyclization of polymers at a specific temperature, thereby enhancing the electrical conductivity of the polymer. Through the examination of mechanical and electrical characteristics, our proposed electrode structure demonstrates improved electrical conductivity while preserving electrode integrity when compared to the conventional SiMP electrode structure. In conclusion, our novel electrode structure presents a promising solution for enhancing the applicability of SiMPs in LIB electrode materials. This advancement holds potential for overcoming challenges associated with SiMPs, thus facilitating their broader utilization in next-generation lithium-ion batteries.

Electrospun LiCoPO4@C Composite Nanofibers As High-Voltage Cathode Materials for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) have revolutionized modern technology with their high energy density allowing longer use in portable electronic devices. Their long cycle life and negligible memory effect further enhance their appeal [1]. However, there are challenges such as lower power density, safety risks including thermal runaway, and an aging effect requiring further development [2].Lithium cobalt phosphate (LCP) offers a possibility of high energy density, owing to its high working potential of 4.8 V vs. Li/Li+ and moderate theoretical capacity of 167 mAh g-1. Furthermore, good thermal stability of LCP can further contribute to the efficient use of LIBs [3]. Despite these advantages, the electrochemical performance of LCP is affected by low ionic and electrical conductivities which cause poor cycle life and rate capability [4]. These limitations could also be accompanied by electrolyte selection and its decomposition at high voltages during delithiation-lithiation of LCP [2] . Thus, this research aims to improve the overall characterizations of LCP@C cathode materials by synthesizing continuous, free-standing nanofibers using the environmentally friendly electrospinning method and implementing nanosize structure enhancing ionic diffusivity [4]. The effect of pre-oxidation temperatures on electrochemical performance of LCP@C cathode materials is studied as well.The electrospinning solution was prepared as previously reported [5] but with a difference of adding a stoichiometric amount of lithium nitrate and electrospun at specified electrospinning parameters. The fibers underwent heat treatment at 700 ℃ in a nitrogen environment after being dried at 150 ℃ and pre-oxidized at various temperatures, indicated in samples’ names. By using scanning electron microscopy (SEM, Crossbeam500, Zeiss) and X-ray diffraction (XRD, Miniflex, Rigaku), the crystal structure and morphology of nanofibers were investigated, respectively.Using CR2032 coin-type cells built in a glove box with 99.9995% pure Ar gas, the electrochemical performance was tested. The cells were equipped with Li chips as reference electrodes, polypropylene separators, ~50 μL of an electrolyte solution comprising 1 M LiPF6 in a mixture of ethylene carbonate and dimethyl carbonate (EC:DMC=1:1 vol.) solvents, and LCP@C composite nanofibers as free-standing cathodes with mass loading of ~2 mg cm-2. At a current density of 0.1 C, the cells were tested in the potential range of 3.5 – 5.3 V vs. Li/Li+. Formation of LCP in the samples have been verified via XRD analysis given in Fig. 1 a, showing a similar pattern for all six samples pre-oxidized at 280-380 ℃. The peak around 22-23 ℃ corresponds to the presence of lithium phosphate for the LCP@C-280 sample. The SEM image in Fig. 1 b shows the formation of nanofibers with beads on materials, the average diameter of fibers is 280-330 nm. Electrochemical performance of prepared LCP@C nanofibers will be presented at the conference. Acknowledgements This research was funded by the projects AP19675260 “Development of nanofibrous electrode materials for next-generation lithium-ion batteries”and AP13068219 “Development of multifunctional free-standing carbon composite nanofiber mats” from the Ministry of Education and Science of the Republic of Kazakhstan.

Surface effects in Mode III fracture of flexoelectric bodies

Flexoelectric materials exhibit mechano-electro coupling between the strain gradients and electric polarization (direct flexoelectricity) and/or between electric field gradients and elastic strains (converse flexoelectricity). As the design of flexoelectric structures is required more and more at decreasing length scales, surface effects become more significant, often resulting in considerable size effects which affect overall deformation of the structure. This further complicates fracture mechanisms in flexoelectric materials particularly at micro- and nano-sized structures. In this paper, we incorporate surface effects with the direct flexoelectricity, to study the electro-mechanical coupling effects of a Mode III crack at the nanoscale structures. We derive the corresponding governing equations together with the associated boundary conditions. Using Williams’ eigenfunction expansion and the J-integral’s path independence, we have obtained the asymptotic field to analyze the singularity indices at the Mode III crack tip in flexoelectric materials. With the use of Fourier transforms, the corresponding mixed boundary value problem is reduced to a hypersingular integro-differential equation in which surface effects are incorporated explicitly. The resulting hypersingular integral equation is solved numerically using Chebyshev polynomials. The influence of both surface and flexoelectric effects on the displacement field, polarization field, strain gradient field along with the actual physical stress field are revealed and displayed graphically.

An Update on Emerging Regenerative Medicine Applications: The Use of Extracellular Vesicles and Exosomes for the Management of Chronic Pain.

Chronic pain affects nearly two billion people worldwide, surpassing heart disease, diabetes, and cancer in terms of economic costs. Lower back pain alone is the leading cause of years lived with disability worldwide. Despite limited treatment options, regenerative medicine, particularly extracellular vesicles (EVs) and exosomes, holds early promise for patients who have exhausted other treatment options. EVs, including exosomes, are nano-sized structures released by cells, facilitating cellular communication through bioactive molecule transfer, and offering potential regenerative properties to damaged tissues. Here, we review the potential of EVs and exosomes for the management of chronic pain. In osteoarthritis, various exosomes, such as those derived from synovial mesenchymal stem cells, human placental cells, dental pulp stem cells, and bone marrow-derived mesenchymal stem cells (MSCs), demonstrate the ability to reduce inflammation, promote tissue repair, and alleviate pain in animal models. In intervertebral disc disease, Wharton's jelly MSC-derived EVs enhance cell viability and reduce inflammation. In addition, various forms of exosomes have been shown to reduce signs of inflammation in neurons and alleviate pain in neuropathic conditions in animal models. Although clinical applications of EVs and exosomes are still in the early clinical stages, they offer immense potential in the future management of chronic pain conditions. Clinical trials are ongoing to explore their therapeutic potential further, and with more research the potential applicability of EVs and exosomes will be fully understood.

Light-Controlled Interconvertible Self-Assembly of Non-Photoresponsive Suprastructures

Achieving light-induced manipulation of controlled self-assembly in nanosized structures is essential for developing artificially dynamic smart materials. Herein, we demonstrate an approach using a non-photoresponsive hydrogen-bonded (H-bonded) macrocycle to control the self-assembly and disassembly of nanostructures in response to light. The present system comprises a photoacid (merocyanine, 1-MEH), a pseudorotaxane formed by two H-bonded macrocycles, dipyridinyl acetylene, and zinc ions. The operation of such a system is examined according to the alternation of self-assembly through proton transfer, which is mediated by the photoacid upon exposure to visible light. The host–guest complexation between the macrocycle and bipyridium guests was investigated by NMR spectroscopy, and one of the guests with the highest affinity for the ring was selected for use as one of the components of the system, which forms the host–guest complex with the ring in a 2:1 stoichiometry. In solution, a dipyridine and the ring, having no interaction with each other, rapidly form a complex in the presence of 1-MEH when exposed to light and thermally relax back to the free ring without entrapped guests after 4 h. Furthermore, the addition of zinc ions to the solution above leads to the formation of a polypseudorotaxane with its morphology responsive to photoirradiation. This work exemplifies the light-controlled alteration of self-assembly in non-photoresponsive systems based on interactions between the guest and the H-bonded macrocycle in the presence of a photoacid.

Breaking barriers of CeO2 in energy storage: Hydrothermal energized preparation of mesoporous carbon added CeO2 nanohybrids as supercapacitor electrodes

Inspired by the excellent physio-chemical properties of nano-sized materials, this study details the hydrothermal preparation and electrochemical characterization of mesoporous carbon added CeO2 nanostructures towards the energy storage applications. Cubic CeO2 is observed for the crystal structure and phase of the prepared materials. The formation of nano-sized (∼ 7 nm) quasi spherical-like structure is found from the TEM analysis and it is mainly ascribed to the combined effect of mesoporous carbon and hydrothermal treatment. The charge storage performance of the prepared composites is examined using three-electrode mode. The capacitive behaviour of mesoporous carbon is additionally supported for electrochemical performance in addition to the battery-like behavior of the CeO2 electrodes resulting in an increase of specific capacity by 102.6 %. Hybrid supercapacitor cell is devised and it could yield a specific energy of 31 W h kg–1 (562 W kg–1) and retain 81 % capacity after 3000 continuous charge discharge cycles. With this efficient composite, the future of energy storage may pave the way for more sustainable and powerful energy solutions.

Temperature-dependent evolution of synthetic coal-derived graphite fillers and their reinforcement in styrene butadiene rubber composites

This study investigated the structural evolution of synthetic coal-derived graphite (SCG), produced from anthracite through high-temperature treatments ranging from 1000 to 2900 °C, and its reinforcement potential in styrene butadiene rubber (SBR) composites. Upon heating the anthracite to 2000 °C, We observed a gradual structural transformation from an amorphous carbon structure with mixed sp2-sp3 bonding to an ordered sp2-bonded nano-sized graphitic structure. This transformation was accompanied by the evaporation of heteroatom functional groups, an increase in high surface energy site as well as micropore and void structures, and enhanced hydrophobic surface property. Beyond 2000 °C, a flake-like graphite with a larger particle size (average lateral size >10 μm) was gradually formed through lateral and vertical crystalline growth mechanisms. The reinforcing potential of SCG fillers was revealed by incorporating them into SBR and evaluating the properties of the resulting composites. It was found that the tensile strength and 300 % tensile modulus initially enhanced with SCG fillers treated up to 2000 °C, but decreased for fillers treated at 2300 and 2900 °C. On the other hand, storage modulus, tear resistance, and gas permeability consistently improved with fillers treated at higher temperatures. These findings highlight the relationship between the temperature-induced structural evolution of SCG fillers and their reinforcement performance in SBR composites, offering valuable insights for industrial rubber applications, particularly enhancing the performance and sustainability of automotive tire.

Structure and mechanical properties of low-density AlCrFeTiX (X = Co, Ni, Cu) high-entropy alloys produced by spark plasma sintering

In this study, low-density (< 6 g/cm3) AlCrFeTiX (x = Co, Ni, Cu) high-entropy alloys were produced by mechanical alloying and spark plasma sintering (SPS), and their structures and mechanical properties after SPS and annealing at 1000 °C for 24 h were reported. Both after SPS and annealing, the AlCrFeTiX (x = Co, Ni, Cu) alloys consisted of an L21 matrix phase with embedded bcc and C14 Laves phase particles. All the alloys had a nano-sized structure after SPS that retained in the AlCrFeTiCo and AlCrFeTiNi alloys after annealing. In the AlCrFeTiCu alloy, the annealing led to a coarsening, with an increase in the size of structural constituents above 1 μm. Compression tests showed that the AlCrFeTiX (x = Co, Ni, Cu) alloys after SPS were brittle at 25 °C, but the AlCrFeTiCo alloy exhibited the highest peak strength of 3792 MPa. At 600 °C, the AlCrFeTiCo alloy after SPS also demonstrated the best performance, with the yield strength, peak strength, and plastic strain of 1960 MPa, 2121 MPa, and 1.8 %, respectively. The annealing did not eliminate the room-temperature brittleness, but improved the mechanical properties at 600 °C. The AlCrFeTiCo alloy showed a 15 %-increase in yield strength (2264 MPa) and more than 2.5 times higher compressive plasticity (4.7 %). The AlCrFeTiNi alloy became more ductile (1 %) and stronger (2200 MPa). For the AlCrFeTiCu alloy, the annealing had a negative effect that resulted in a halved plasticity at 600 °C. The AlCrFeTiCo and AlCrFeTiNi alloys after annealing showed record-high specific yield strength values at 600 °C, which were 383 and 371 MPa*cm3/g, respectively. With these values, the AlCrFeTiCo and AlCrFeTiNi alloys outperformed all the low-density medium-/high-entropy alloys available in literature to date obtained both by SPS or conventional casting. The structure formation and mechanical properties, as well as the response of these features to annealing, were extensively discussed.

Controlled Fabrication of Unimolecular Micelles as Versatile Nanoplatform for Multifunctional Applications.

Unimolecular micelles (UMs) are nano-sized structures that are composed of single molecules with precise composition. Compared to self-assembled polymeric micelles, UMs possess ultra-stable property even in complex biological environment. With the development of controllable polymerization and coupling chemistry, the preparation of narrowly monodispersed UMs with precise morphology and size has been realized, which further facilitates their multifunctional applications. After brief introduction, state-of-the-art advances in the synthesis and applications of UMs are discussed with an emphasis on their bioapplications. It is believed that these UMs have great potential in future fabrication of multifunctional nanoplatforms.

Polyvinyl Alcohol Capped Silver Nanostructures for Fortified Apoptotic Potential Against Human Laryngeal Carcinoma Cells Hep-2 Using Extremely-Low Frequency Electromagnetic Field.

: Polyvinyl alcohol-capped silver nanostructures (cAgNSs) were investigated in order to enhance the cytotoxicity, pro-apoptotic, and oxidant patterns of in human laryngeal carcinoma Hep-2 cells by employing a 50 mT electromagnetic field (LEMF) for 30 min. Wet chemical reduction was used to synthesize the cAgNSs, and after they had been capped with polyvinyl alcohol, they were specifically examined for particle size analysis and structural morphology. To visualize how the silver may attach to the protein targets, a molecular docking study was conducted. Estimation of cytotoxicity, cell cycle progression supported by mRNA expression of three apoptotic-promoting genes and one apoptotic-resisting. Particle size analysis results were a mean particle size of 157.3±0.5 nm, zeta potential value of -29.6 mV±1.5 mV, and polydispersity index of 0.31±0.05. Significantly reduction of IC50 against Hep-2 cells by around 6-fold was concluded. Also, we obtained suppression of the proliferation of Hep-2 cells, especially in the G0/G1 and S phases. Significant enhanced mRNA expression revealed enhanced induced CASP3, p53, and Beclin-1 mediated pro-apoptosis and induced NF-κB mediated autophagy in Hep-2 cells. Augmented levels of GR, ROS and MDA as oxidative stress biomarkers were also obtained. HE staining of Hep-2 cells exposed to cAgNSs and LEMF confirmed the enhanced apoptotic potential comparatively. By conclusion, the developed nano-sized structures with the aid of extremely-low frequency electromagnetic field were successful to fortify the anti-cancer profile of cAgNSs in Hep-2 cells.

Synthesis of oleic acid – coated zinc – doped iron boride nanoparticles for biomedical applications

Although various iron-based magnetic materials have been extensively studied in biomedical field for many years, iron boride compounds with interesting chemical and magnetic properties are relatively less explored, and their potential applications are not as widely known. In this study, the synthesis, coating, surface modification, and cytotoxicity tests of the Fe–Zn–B system were presented. Iron boride-based nanoparticles (NPs) containing elemental zinc (Zn) were developed by using a direct chemical synthesis of FeCl3, ZnCl2 and NaBH4, and investigated for potential use in biomedical applications. Powders having the phases of pure FeB with small amount of elemental Zn were obtained with a uniform morphology and an average particle size of 68 nm. The NPs were then coated with oleic acid (OA) and surface modified with sodium tricitrate, to increase their stability and biocompatibility, and well-dispersed NPs were obtained with sizes below 30 nm. TEM investigations revealed the presence of hybrid clusters with nanoparticle – OA structures, indicating that FeB nanoparticles were stabilized by being embedded in OA clusters, forming both agglomerated sub-micron and free nano-sized structures. Obtained NPs showed ferromagnetic property, with a saturation magnetization of 25.9 emu/g and a low coercivity of 90 Oe. As a result of testing different types of healthy and cancer cell lines with NPs, Zn-doped-FeB@OA NPs exhibited a high biocompatibility. Results suggested that highly biocompatible and magnetic OA-coated Zn-doped FeB particles can be potential candidates for biomedical applications such as medical imaging or drug delivery systems.

Engineered hybrid carbon nanohorns-lipid platforms for the delivery of cisplatin to the colorectal cancer

Carbon nanostructures are considered distinctive multi-functional drug delivery platforms for cancer therapy. However, their potential biocompatibility is still a significant challenge and rational design of these carriers is a prospect in the context of efficient cancer therapy. Herein, we report on the synthesis of two bio-inspired carbon nanohorns (CNH) platforms with tumor targeting capabilities for the delivery of cisplatin. Oxidized CNH wrapped with either polyethylene glycol (PEG) and fusogenic lipids (PEG/DSPG CNH-CP) or glutamic acid-cisplatin complex (CNH-GA-CP), revealed nanosized dahlia-like structure approved by dynamic light scattering (DLS) and transmission electron microscopy (TEM) analysis. Further structure features analysis by using RAMAN, FTIR spectroscopy and TGA indicated CNH surface modification. Excitingly, the superior nanofeatures of the CNH platforms was due to the reduced hydrophobic interactions, and thus closely linked to the surface modifications. Both platforms preserved cisplatin toxicity in vitro on C26 cells. The PEGylated nanoplatform demonstrated elongated circulation time compared to the free drug, and showed a site-specific delivery to the tumor site, while reducing the accumulation within kidney. Following 3 i.v. doses at 3 mg/kg of cisplatin, PEGylated CNH significantly delayed tumor growth and improved the life span of C26-bearing BALB/c mice. These notable results were further approved by the histopathological data, demonstrating reduced degeneration, necrosis and inflammation in both kidney and liver tissues following PEGylated nanoplatform administration. In conclusion, our findings suggest that the systemic toxicity of cisplatin including nephrotoxicity can be resolved by delivering this chemotherapeutic through a rationally-fabricated surface-modified carbon nanoplatform to improve the cancer therapy outcome.

Crack propagation arrest by the Joule heating in micro/nano-sized structures

The Joule heating technique is utilized to arrest the crack propagation so to protect some important structures being further damaged. In this approach there are created compression stresses at the crack tip vicinity due to a specific temperature distribution induced by the electric current. The Joule heating is amulti-physical problem which is applied here to micro/nano-sized structures. The size-effects are considered for description of both the elastic and the thermal fields. The heat conduction can’t be well described by classical Fourier’s law in nano-sized structures. A novel gradient theory is developed in such structures adopting the size effect of heat conduction. Besides, the strain gradients and double stresses are introduced into the constitutive laws. Then, the governing equations are given by partial differential equations with order of derivatives being higher than in classical theory. The principle of virtual work is the base of weak formulation and derivation of the discretized finite element equations for ageneral 2d boundary value problem with cracks. The collocation mixed FEM with large strain gradients is developed for numerical solution, where the C0 continuous approximation is applied independently to displacements and strains and also to temperature and temperature gradients. Kinematic constraints between strains and displacements are satisfied by the collocation method at selected interior points. The collocation mixed FEM is applied to solve 2D crack problems with Joule heating.

Biologically inspired shell-hollow particles for designing efficient passive all-sky radiative cooling

Passive radiation cooling (PRC), as the most promising technology to meet future cooling needs, has attracted great interest. However, there are still huge challenges in manufacturing high-efficiency and low-cost radiant coolers suitable for all-day use. Here, we report a secondary micro-nano shell-hollow structure based on blending method, inspired by the African white beetle Goliathus goliatus. Due to the difference in reflectance between the shell and the internal air, compared with the homogeneous particles, the scattered light has a changed optical path at the interface of the core (air) and the shell (SiO2), and most of the light escapes from the particles, showing strong total internal reflection. The design ingeniously deposits the nano-sized shell-hollow structure on the surface of the micron-sized shell-hollow structure, achieving high solar reflectance (95 ​%)and excellent long-wave infrared emissivity (94 ​%). Sub-ambient cooling of 7.8 and 4.7 ​°C can be achieved at night and daytime, respectively. Silica microspheres with shell and hollow structure can be prepared by soft template method, which is mature, reliable, simple and cheap.Our work provides new ideas for the design and manufacture of high-performance Passive all-day radiative cooling (PARC).

Evaluating various properties of nanohydroxyapatite synthesized from eggshells and dual-doped with Si4+ and Zn2+: An in vitro study

BackgroundThis study aimed to evaluate morphological, chemical and biocompatible properties of nanohydroxyapatite (N-HA) synthesized from eggshells and dual-doped with Si4+ and Zn2+. MethodsIn the current study, N-HA was synthesized from chicken eggshells using the wet chemical precipitation method and doped with Si4+ and Zn2+. The physical assessment was carried out using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) analysis, and X-ray diffraction (XRD) analysis. Crystal size was calculated using the Scherrer equation. Cytotoxicity was studied in vitro using the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) cytotoxicity assay. The optical density (OD) of each well was obtained and recorded at 570 nm for 24 h (t1), 48 h (t2), 72 h (t3), and 5 days (t4) using a microplate reader. ResultsThe results of Si–Zn-doped HA showed a high specific surface area with an irregular nano-sized spherical particle structure. The atomic percentage provided the ratio of calcium to phosphate; for non-doped HA, the atomic Ca/P ratio was 1.6, but for Si–Zn-doped HA, where Zn+2 Ca and Si + replaced 4 substituted P, the atomic ratio (Ca + Zn)/(P + Si) was 1.76. The average crystal size of Si–Zn-doped HA was 46 nm, while for non-doped HA it was 61 nm. both samples were non-toxic and statistically significantly less viable than the control group After 5 days, the mean cell viability of Si–Zn-doped HA (79.17 ± 2.18) was higher than that of non-doped HA (76.26 ± 1.71) (P = 0.091). ConclusionsThe MTT assay results showed that Si–Zn-doped HA is biocompatible. In addition, it showed characteristic physiochemical properties of a large surface area with interconnected porosity.

Classification of rotation-invariant biomedical images using equivariant neural networks

Transmission electron microscopy (TEM) is an imaging technique used to visualize and analyze nano-sized structures and objects such as virus particles. Light microscopy can be used to diagnose diseases or characterize e.g. blood cells. Since samples under microscopes exhibit certain symmetries, such as global rotation invariance, equivariant neural networks are presumed to be useful. In this study, a baseline convolutional neural network is constructed in the form of the commonly used VGG16 classifier. Thereafter, it is modified to be equivariant to the p4 symmetry group of rotations of multiples of 90° using group convolutions. This yields a number of benefits on a TEM virus dataset, including higher top validation set accuracy by on average 7.6% and faster convergence during training by on average 23.1% of that of the baseline. Similarly, when training and testing on images of blood cells, the convergence time for the equivariant neural network is 7.9% of that of the baseline. From this it is concluded that augmentation strategies for rotation can be skipped. Furthermore, when modelling the accuracy versus amount of TEM virus training data with a power law, the equivariant network has a slope of − 0.43 compared to − 0.26 of the baseline. Thus the equivariant network learns faster than the baseline when more training data is added. This study extends previous research on equivariant neural networks applied to images which exhibit symmetries to isometric transformations.