Thin Sheets Research Articles

A metasurface-on-fiber light-sheet generator for biological imaging

Light sheet has been widely used for bioimaging. However, it is a big challenge to build a miniature light-sheet imaging system due to geometric constraints of bulky refractive and diffractive elements. Metasurface-based devices composed of subwavelength unit cells, with compact size and the ability to effectively manipulate optical fields, have been considered as potential planar analogs of conventional components to realize various functionalities. Integrating metasurfaces onto an optical fiber facet is sparking new ideas and emerging applications. Here, we propose a metasurface-on-fiber light-sheet generator, which can convert a fiber mode to a thin light sheet. By adopting a multi-core fiber and a dielectric metasurface on its facet, a light sheet with a thickness of 2 μm and a length of 83.0 μm is obtained. The generator can greatly simplify the illumination of light sheet imaging systems and be flexibly used for advanced biological imaging applications.

Influence of IP-TIG welding parameters on weld bead geometry, tensile properties, and microstructure of Ti6Al4V alloy joints

Abstract The primary aim of this study is to analyze the influence of inter-pulse tungsten inert gas (IP-TIG) welding parameters (peak current, inter-pulse current, and inter-pulse frequency) on weld bead geometry, tensile properties, and microstructure of Ti6Al4V alloy joints for gas turbine applications. IP-TIG welding principally featured by magnetic arc constriction and pulsing was employed to overcome the high heat input problems in TIG welding of thin Ti6Al4V alloy sheets such as wider bead and HAZ, coarsening of beta grains, inferior ductility, distortion of joints, and atmospheric contamination which significantly deteriorates the mechanical performance of welded sheets. The tensile properties and microhardness of IP-TIG joints were evaluated and correlated to the microstructural features. The microstructural features were analyzed using optical microscopy. The fractured surfaces of tensile specimens were studied using scanning electron microscopy. Results showed that the Ti6Al4V alloy joints developed using peak current of 50 A, inter-pulse current of 30 A, and inter-pulse frequency of 20 kHz exhibited greater strength, hardness and elongation. It showed greater tensile strength of 1030 MPa, yield strength of 981 MPa, and elongation of 10 % and FZ microhardness of 391 HV0.2. It is mainly due to the development of refined grains in fusion zone (FZ).

Seismic flexural behavior of CFRP strengthened reinforced concrete beams secured with fiber anchors

An experimental program was conducted to examine the seismic performance of flexural beam members strengthened with carbon fiber-reinforced polymer (CFRP) sheet and anchored using carbon fiber splay anchors. This research study extends the use of carbon fiber anchors to secure the top and bottom CFRP flexural sheets under cyclic loading. In this study, low strength concrete is examined, with lightly reinforced steel ratio (0.0034) to test full-scale rectangular beams. Five reinforced concrete beams were cast, strengthened, and tested under reversed cycles of four-point bending to failure. The beams were categorized into a control specimen, strengthened specimens with thin sheets with and without fiber anchors, and strengthened specimens with thick sheets with and without fiber anchors. They were tested cyclically under displacement control according to the AC 125 loading protocol. The failure modes ranged from classical ultimate failure for the control beam to rupture and intermediate crack (IC) debonding for the beam with unanchored thin CFRP sheets. On the other hand, debonding took place for the thicker sheets with no anchors, while the thicker sheets with fiber anchors underwent cover delamination failure mode despite the fact that the sheets were extended very close to the simple supports. The hysteresis response loops were compared for the different specimens and the analytical envelop curves were predicted resulting in a close agreement to the experimental finding.

Amnion-derived hydrogels as a versatile platform for regenerative therapy: from lab to market.

In recent years, the amnion (AM) has emerged as a versatile tool for stimulating tissue regeneration and has been of immense interest for clinical applications. AM is an abundant and cost-effective tissue source that does not face strict ethical issues for biomedical applications. The outstanding biological attributes of AM, including side-dependent angiogenesis, low immunogenicity, anti-inflammatory, anti-fibrotic, and antibacterial properties facilitate its usage for tissue engineering and regenerative medicine. However, the clinical usage of thin AM sheets is accompanied by some limitations, such as handling without folding or tearing and the necessity for sutures to keep the material over the wound, which requires additional considerations. Therefore, processing the decellularized AM (dAM) tissue into a temperature-sensitive hydrogel has expanded its processability and applicability as an injectable hydrogel for minimally invasive therapies and a source of bioink for the fabrication of biomimetic tissue constructs by recapitulating desired biochemical cues or pre-defined architectural design. This article reviews the multi-functionality of dAM hydrogels for various biomedical applications, including skin repair, heart treatment, cartilage regeneration, endometrium regeneration, vascular graft, dental pulp regeneration, and cell culture/carrier platform. Not only recent and cutting-edge research is reviewed but also available commercial products are introduced and their main features and shortcomings are elaborated. Besides the great potential of AM-derived hydrogels for regenerative therapy, intensive interdisciplinary studies are still required to modify their mechanical and biological properties in order to broaden their therapeutic benefits and biomedical applications. Employing additive manufacturing techniques (e.g., bioprinting), nanotechnology approaches (e.g., inclusion of various bioactive nanoparticles), and biochemical alterations (e.g., modification of dAM matrix with photo-sensitive molecules) are of particular interest. This review article aims to discuss the current function of dAM hydrogels for the repair of target tissues and identifies innovative methods for broadening their potential applications for nanomedicine and healthcare.

Hybrid Joining of Dissimilar Thin Metallic Sheets—Mechanical Joining and Adhesive Bonding

This paper deals with joining dissimilar materials using thermal drilling technology as well as the combination of thermal drilling and adhesive bonding. The base materials for the experimental work were deep-drawn low-carbon steel DC04, HSLA steel TL 1550-220 + Z, and structural aluminum alloy EN AW-6082 T6 (AlSi1MgMn). The geometry of the formed joints was tested metallographically as the load-bearing shear capacity under the tensile shear test of single-lapped joints and the resistance of the joints against corrosion-induced disbonding in a climate chamber. The energy dissipated by the joints up to fracture was calculated from the load–displacement curves. The hybrid joints were compared with the bonded joints with the same overlap area in terms of the load-bearing capacity and energy dissipated at joint failure. The hybrid joints formed by thermal drilling and adhesive bonding with a rubber-based adhesive confirmed the synergistic effect—the adhesive provides the high load-bearing capacity of the joint, and the bushing formed by thermal drilling increases the dissipated energy of the joint at failure. The exposure of the joints in the climatic chamber did not cause a relevant reduction in the characteristics of the joints.

The Characterization of the Plastic Instability of S235 Thin Steel Sheets by Multiple Regression and Analysis of Variance Methods

In this study, we present a new identification method of parameters characterizing the elastoplastic damage behavior of sheet metal based on analysis of variance. The analysis covered experimental and numerical simulation results using the finite element method of the sheet mild steel bulge test. The identification procedure was validated through a confrontation between numerical simulations and experimental results on several hydroforming applications, such as a free expansion and an expansion in matrix cavities. Results show consistency between experimental observations and numerical predictions of instabilities. Furthermore, the location of risk areas of instability and rupture and the damage level could be quantified. The analysis focused on a set of results combining experimental data and numerical simulations of the bulge test of steel sheets. The identified models were validated thanks to a comparison between numerical simulations and experimental results of a set of forming applications by bulge test. The results show coherence between the experimental observations and the numerical predictions of the instabilities.

Improving coffee capsules recyclability - A combined assessment of circularity and environmental performance of a novel design

Coffee capsules have gained high levels of popularity in the last decades due to their convenience of use, flavour choices, and consistent extraction quality. As governmental bodies are promoting more circular solutions for packaging products, concerns have been raised regarding the environmental impacts of single-use coffee capsules, namely their end-of-life treatment and effective recyclability. This paper presents a novel design based on thin steel sheet material application for new packaging solutions that can support a more circular economy. To validate this new design, a framework was presented for a cross-assessment of Life Cycle Assessment with Circularity Analysis to compare the new tinplate capsule with conventional polypropylene and aluminium capsules. The novel design is more circular (0.97 in the material circularity indicator), in comparison with the polypropylene (0.1) and aluminium (0.80) conventional capsules, due to the ferromagnetic properties that allow for better effectiveness during sorting in urban packaging recycling facilities. As for the environmental assessment, the tinplate has higher environmental impacts than the aluminium and the polypropylene capsules (more 63 % and more 92 %, respectively) due to the high energy intensity processes required to produce this material. These results demonstrate that the novel tinplate capsule should complement the strong results in circularity with further improvements in its environmental performance, namely by the transition of the steel industry to the upcoming generation of decarbonized steel production.

Damage and fracture initiation under shear and compression stress states in the aluminum alloy EN AW6082-T6

The present paper deals with the experimental and numerical analysis of damage and fracture behavior of ductile metals under combined compression and shear loading. Biaxial experiments with the H-specimen using a pneumatic downholder during compression loading and corresponding numerical simulations are discussed. A thermodynamically consistent anisotropic continuum damage model using damage strains is presented. During the experiments strain fields in critical areas of the specimens are monitored by digital image correlation (DIC) technique also showing evolution of deformation in thickness direction of thin sheets. Corresponding numerical simulations reveal the stress states and details of inelastic deformation behavior.

Characterization of Shrink Film Properties for Rapid Microfluidics Lab-on-Chip Fabrication.

Shrink film is a thin sheet of polystyrene plastic that shrinks to 25-40% of its original size when heated. This study investigated the shrinkage factor of the film at different temperatures and baking times to determine the optimal fabrication recipe for shrink film microfluidic device production. Additionally, this study characterized the properties of shrink film, including minimum possible feature size and cross-section geometries, using manual engraving and the CAMEO 4 automated cutting machine. The optimal shrinkage factor ranged from 1.7 to 2.9 at 150 °C and a baking time of 4 min, producing the ideal size for microfluidic device fabrication. The X- and Y-axes shrank ~2.5 times, while Z-axis thickened by a factor of ~5.8 times. This study achieved a minimum feature size of 200 microns, limited by the collapsing of channel sidewalls when shrunk, leading to blockages in the microchannel. These findings demonstrate the feasibility and versatility of using shrink film as a cost-effective and efficient material for the rapid fabrication of microfluidic devices. The potential applications of this material in various fields such as the medical and biomedical industries, bacteria and algae culture and enumeration are noteworthy.

Enhancing Hydrogen Evolution Catalysis through Potential-Induced Structural Phase Transition in Transition-Metal Dichalcogenide Thin Sheets.

Enhancing electrocatalytic performance relies on effective phase control, which influences key catalytic properties, such as chemical stability and electrical conductivity. Traditional methods for manipulating the phase of transition-metal dichalcogenides (TMDs), including high-temperature synthesis, Li intercalation, and doping, involve harsh conditions and energy-intensive processes. This study introduces an innovative approach to crafting heterophase structures (2H-1T-WS2) in TMDs, using WS2 as a model compound, encompassing both semiconducting (2H) and metallic (1T) types through a straightforward potential activation method. Insights from in situ electrochemical Raman spectroscopy, HR-TEM, and XPS measurements reveal distinctive partial phase-transition behavior. This behavior enables the partially exposed basal plane of 2H-1T-WS2 to demonstrate superior activity in the hydrogen evolution reaction (HER), attributed to enhanced electrical conductivity and the exposure of highly active sites. The potential-induced phase transition presents promising avenues for the development of catalysts with heterophase structures.

A hybrid approach towards evaluation of average heat transfer coefficient in twin-roll strip casting mold

Continuous casting stands out as one of the most efficient and productive methods for producing billets, slabs, or thin sheets while conserving energy. Understanding the solidification dynamics and achieving defect-free sheets in continuous casting necessitates the accurate prediction of heat transfer coefficient (HTC) at the mold metal interface. Accurate prediction of HTC helps in selecting process parameters such as superheat temperature and casting velocity, which directly affect the production rate and quality of the cast component. Determining the HTC is a complex process, as it is influenced by various process parameters such as casting size, casting speed, superheat temperature, surface roughness, type of water used as a coolant, nozzle design and wettability. Therefore, the present study proposed a hybrid approach for finding HTC in a twin roll strip casting mold through a solidified shell shape, which is influenced by the factors affecting the heat transfer at the mold-metal interface. This approach integrates the experimental and simulation investigations. The numerical investigation used a three-dimensional coupled fluid flow and heat transfer equations with an assumed range of HTC (100–2000 W/(m2K)). The solidified shell shape for different HTCs was compared with the experimental solidified shape form at the outer wall of the mold using the solidification criteria. Results indicate that the initial HTC range of 100–1000 W/(m2K) does not lead to blockage of the graphite mold outlet. However, as HTC values approach 1000 W/(m2K) to 1400 W/(m2K), the melt obstructs the mold exit based on solidification criteria. The HTC values (1350 ± 150 W/(m2K)) obtained from the proposed methodology for mold, align well with the HTC values (1183 ± 593 W/(m2K)) calculated using lamellar spacing of the Al-Mg2Si composite microstructure. This hybrid approach presents a novel and straightforward method for determining HTC, offering accurate predictions that can enhance the precision of continuous casting models and provide a more nuanced understanding of solidification behavior.

Chemical Characteristics of Kepok Banana Bud (Musa Paradisiaca Linn.) Flakes with Variations of Mocaf Flour

Flakes are food products that have the shape of thin sheets, brownish yellow in color with a practical presentation. Flakes are easy to process and generally consumed for breakfast. Flakes that are rich in dietary fiber and protein can serve as a source of energy while also offering functional advantages. The objective of this study is to generate flakes with elevated levels of dietary fiber and protein by utilizing mocaf and yellow kepok banana bud flour. The use of mocaf flour in the manufacture of flakes intends to improve the fiber content, while the use of yellow kepok banana bud (YKBB) flour aims to boost the protein level. This research was conducted to determine the chemical characteristics of flakes with variations of mocaf flour and KBF. The chemical characteristics include moisture, ash, crude fiber, total protein, lipid, and carbohydrate content. This study used a completely randomised design (CRD) with 2 replications with a ratio of wheat flour, mocaf flour, and YKBB flour as much as the control (20g:0g:0g), F1 (10g:10g:0g), F2 (10g:2.5g:7.5g), F3 (10g:5g:5g) and F4 (10g:7.5g:2.5g). The results showed that the moisture content was 2.43–3.19% w.b., the ash content was 2.55–11.72% d.b., the crude fiber content was 2.17–8.40% d.b., the total protein content was 4.34–7.85% d.b., lipid content 2.46–3.17% d.b., and carbohydrate content was 76.91–87.98% d.b.

Mechanical properties and corrosion resistance study of dissimilar metal thin sheet friction stir welded joints

This study employs friction stir welding (FSW) technology to achieve the butt welding of 2mm thick 1060 aluminum and T2 copper. The research investigates the macroscopic formation, tensile properties, microhardness, and electrochemical corrosion behavior of the welded joints. The results indicate that the welded joints exhibit excellent formation, with a tensile strength reaching 84.76% of that of the 1060 aluminum material. Well-formed welded joints can be obtained by controlling the rotation speed and welding speed within a certain range. However, the rotation speed has a more significant impact on the microhardness in the weld zone. The corrosion potential of T2 copper is higher than that of 1060 aluminum, forming a macroscopic galvanic couple between the two materials. The corrosion potential of the welded joint falls between that of T2 copper and 1060 aluminum.

Welding of thin stainless-steel sheets using a QCW green laser source

Bipolar plates are structured thin metal sheets and are, next to the membrane electrode assembly (MEA), one of the main components of polymer electrolyte membrane fuel cells. One of the production steps of such bipolar plates is the joining process of its two halves. Laser welding is a suitable method for such an application since it is fast, non-contact, automatable, and scalable. Particularly important aspects of the weld seam are the weld seam width and depth. In this paper, welding of stainless-steel material analogous to materials used in bipolar plates is examined. For this purpose, a newly developed quasi continuous wave (QCW) green laser source with higher beam quality is employed to assess the effect of the wavelength and the spot diameter on the welding of stainless-steel material. By using various focusing lens, different sized beam diameters below 20 µm are achieved and their influence on the final welding result—specifically concerning the seam width—are analyzed. With welding speeds starting at 500 mm/s, reduced weld seam widths (≤ 100 µm) are realized, particularly with a focusing lens of 200 mm focal distance. The suitability of such a process for thin channels of under 75 µm width is examined.

Buckling mediated by mobile localized elastic excitations.

Experiments reveal that structural transitions in thin sheets are mediated by the passage of transient and stable mobile localized elastic excitations. These "crumples" or "d-cones" nucleate, propagate, interact, annihilate, and escape. Much of the dynamics occurs on millisecond time scales. Nucleation sites correspond to regions where generators of the ideal unstretched surface converge. Additional stable intermediate states illustrate two forms of quasistatic inter-crumple interaction through ridges or valleys. These interactions create pairs from which extended patterns may be constructed in larger specimens. The onset of localized transient deformation with increasing sheet size is correlated with a characteristic stable crumple size, whose measured scaling with thickness is consistent with prior theory and experiment for localized elastic features in thin sheets. We offer a new theoretical justification of this scaling.

A novel zero tool defect accelerated friction stir thin sheet welding technique for automotive light-weight structural component fabrication with dissimilar material

Frequent tool failure and rupturing pose significant challenges in friction stir welding (FSW) of thin dissimilar material sheets with diverse thermal and mechanical properties. These issues exacerbate at higher welding speed (ν), demanding greater precision in welding methodology. This paper presents a novel approach to weld 300 μm thin SS304 and 500 μm thick commercially pure aluminum sheets at ν up to 2400 mm/min using H13 tool without wear, obviating the necessity for expensive high-strength tool materials. Furthermore, the use of a pinless tool negates the requirement for an additional pinhole filling step, which is a prevalent challenge associated with pinned tools. The study unveils that higher tool tilt angle (α) reduces flash formation, leading to a higher effective weld thickness, thereby enhancing weld strength. The increased material extraction (2.048 mm3) from the weld center and higher heat generation (7.6%) compared to the pinless tool imposes a speed limit of 300 mm/min for the pinned tool. The thicker layer (4.9 μm) of inter-metallic compounds (IMC) formed at lower ν showed maximum joint strength (70.03% of base Al). The fracture behavior indicates cleavage facet formation becomes more frequent at higher ν, diminishing joint ductility. With a distortion-free, high lap shear strength and enhanced ν, this novel joining method meets the needs of industrial mass production.

Investigation of Tool Degradation during Friction Stir Welding of Hybrid Aluminum-Steel Sheets in a Combined Butt and Overlap Joint.

Friction stir welding, as a solid-state welding technique, is especially suitable for effectively joining high-strength aluminum alloys, as well as for multi-material welds. This research investigates the friction stir welding of thin aluminum and steel sheets, an essential process in the production of hybrid tailor-welded blanks employed in deep drawing applications. Despite its proven advantages, the welding process exhibits variable outcomes concerning formability and joint strength when utilizing an H13 welding tool. To better understand these inconsistencies, multiple welds were performed in this study, joining 1 mm thick steel to 2 mm thick aluminum sheets, with a cumulative length of 7.65 m. The accumulation of material on the welding tool was documented through 3D scanning and weighing. The integrity of the resulting weld seam was analyzed through metallographic sections and X-ray imaging. It was found that the adhering material built up continuously around the tool pin over several welds totaling between 1.5 m and 2.5 m before ultimately detaching. This accretion of material notably affected the welding process, resulting in increased intermixing of steel particles within the aluminum matrix. This research provides detailed insights into the dynamics of friction stir welding in multi-material welds, particularly in the context of tool material interaction and its impact on weld quality.

Environmental and Health Impacts of Graphene and Other Two-Dimensional Materials: A Graphene Flagship Perspective.

Two-dimensional (2D) materials have attracted tremendous interest ever since the isolation of atomically thin sheets of graphene in 2004 due to the specific and versatile properties of these materials. However, the increasing production and use of 2D materials necessitate a thorough evaluation of the potential impact on human health and the environment. Furthermore, harmonized test protocols are needed with which to assess the safety of 2D materials. The Graphene Flagship project (2013-2023), funded by the European Commission, addressed the identification of the possible hazard of graphene-based materials as well as emerging 2D materials including transition metal dichalcogenides, hexagonal boron nitride, and others. Additionally, so-called green chemistry approaches were explored to achieve the goal of a safe and sustainable production and use of this fascinating family of nanomaterials. The present review provides a compact survey of the findings and the lessons learned in the Graphene Flagship.

Karakteristik Fruit Leather Buah Pala (Myristica fragrans) Dengan Variasi Jenis Hidrokoloid Gel

Fruit leather is a processed food product from pulp of fruit flesh that has been crushed with the addition of stabilizer then dried in a mold using an oven, so as to form a thin sheet that can be rolled up. The raw material for fruit leather can come from fruits such as nutmeg flesh. The purpose of this study was to determine the physical and chemical characteristics of fruit leather from nutmeg flesh with a variation of 0.3% hydrocolloid gel (CMC, pectin and carrageenan). Parameters observed included color, texture, water content, and pH. The results showed that the physical characteristics of the fruit leather of nutmeg flesh with the addition of carrageenan had a texture value of 0.12 kg/mm2 and a color with an *L value of 27.45; the value of *a is 6.03; the value of *b is 13.20. While the chemical characteristics have a water content value of 22.37% and a pH of 3.56. The addition of CMC has a texture value of 0.28 kg/mm2 and a color value with a *L value of 30.78; the value of *a is 5.94; the value of *b is 12.41. While the chemical characteristics have a water content value of 19.03% and a pH of 3.51. The addition of pectin has a texture value of 0.23 kg/mm2 and a color value of *L, which is 31.02; the value of *a is 5.77; the value of *b is 12.31. While the chemical characteristics have a water content value of 16.61% and a pH of 3.33.

The Influence of TiO2-Lignin Hybrid Fillers in Low-Density Polyethylene Composites on Photocatalytic Performance and UV-Barrier Properties.

The main objective of this study was to discover new packaging materials that could integrate one of the most expected properties, such as UV protection, with a self-cleaning ability defined as photocatalytic performance. Accordingly, new hybrid additives were used to transform LDPE films into materials with complex performance properties. In this study, titanium dioxide-lignin (TL) hybrid systems with a weight ratio of inorganic to organic precursors of 5-1, 1-1, and 1-5 were prepared using a mechanical method. The obtained materials and pristine components were characterized using measurement techniques and research methods, such as Fourier-transform infrared spectroscopy (FTIR), thermal stability analysis (TGA/DTG), measurement of the electrokinetic potential as a function of pH, scanning electron microscopy (SEM), and particle size distribution measurement. It was found that hydrogen bonds were formed between the organic and inorganic components, based on which the obtained systems were classified as class I hybrid materials. In the next step, inorganic-organic hybrid systems and pristine components were used as fillers for a low-density polyethylene (LDPE) composite, 5 and 10% by weight, in order to determine their impact on parameters such as tensile elongation at break. Polymer composites containing titanium dioxide in their matrix were then subjected to a test of photocatalytic properties, based on which it was found that all materials with TiO2 in their structure exhibit photocatalytic properties, whereby the best results were obtained for samples containing the TiO2-lignin hybrid system (1-1). The mechanical tests showed that the thin sheet films had a strong anisotropy due to chill-roll extrusion, ranging from 1.98 to 3.32. UV-Vis spectroscopy revealed four times higher light absorption for composites in which lignin was present than for pure LDPE, in the 250-450 nm range. On the other hand, the temperature at 5% and 30% weight loss revealed by TGA testing increased the highest performance for LDPE/TiO2 materials (by 20.4 °C and 8.7 °C, respectively).