Single-step Manufacturing Research Articles

Body heat energy driven knitted thermoelectric garments with personal cooling

Wearable, thermoelectric (TE) devices have gained significant interest in recent years as they can both generate output power from converting body heat into electrical energy and be utilized in personal cooling through the Peltier effect. Currently, researched wearable TE cooling devices focus on devices that can be attached to the human body in specific locations and use heat sinks or elongated thermoelectric pillars to increase their effectiveness, making them hard and bulky. In addition, these devices are attached, not integrated, to wearable garments, making their manufacturing a multi-step process. To address this issue, we developed a knitted TE garment through a single-step manufacturing process that offers energy generation and personal cooling capabilities. The functioning of the cooling device was mathematically modelled and analyzed to understand its scalability, optimization, and to show its potential. This garment features excellent thermoelectric generation of 7.48 mV and 0.46 mA on the human body, and the ability to cool the human body up to 1.5 °C. The observations proved that the mathematical model could predict the behavior of the TE device closely. The results showed that the proposed method of knitted TE cooling garment manufacturing is a viable and scalable process.

In-situ consolidation of thermoplastic composites by automated fiber placement: Characterization of defects

The emergence of automated manufacturing of composites has not only transformed the manufacturing of optimized and geometrically complex structures but has also expanded the promising prospect of in-situ manufacturing of thermoplastic composites (TPC), where both material placement and consolidation are carried out by automated fiber placement (AFP) equipment, streamlining the process into single step manufacturing. However, the inherent complexities in different aspects of robotic automation, imperfections in the supplied material, and the occurrence of multi-physical phenomena during in-situ consolidation introduce various manufacturing-induced defects. While the defects in thermoset composites (TSC) made by AFP have been widely studied in the past, this study explores the diverse defects at micro and macro scales for TPCs made by AFP, with a focus on carbon-fiber/poly-ether-ether-ketone (CF/PEEK) tapes consolidated using hot gas torch (HGT) heating system. An overview of defects and associated characteristics is presented across three phases: defects in supplied impregnated tapes, defects and limitations in performance of AFP system, and defects in the final in-situ consolidated composite. For the defects subject to studies in the past, the description is limited to a concise review, while those with limited understanding are supported by new empirical observations in this work.

Bio-inspired non-assembly joints: Design, fabrication and wear performance

Additive manufacturing facilitates the materialization of complex designs, e.g. bio-inspired non-assembly joints. Despite the advantages of this type of joints, such as single-step manufacturing, their performance under operational conditions remains poorly understood. This paper explores the design, fabrication and wear performance of a hinge-type joint inspired by the camel elbow. The joint was fabricated by metal additive manufacturing and its wear behaviour was numerically and experimentally evaluated. The results show that the bio-inspired design performs better than a cylindrical one in terms of wear distribution. This work helps to better understand the wear performance of non-assembled bio-inspired joints.

Formulation and processing of solid self-emulsifying drug delivery systems (HME S-SEDDS): A single-step manufacturing process via hot-melt extrusion technology through response surface methodology

The objective of the current study is the formulation development and manufacturing of solid self-emulsifying drug delivery systems (HME S-SEDDS) via a single-step continuous hot-melt extrusion (HME) process. For this study, poorly soluble fenofibrate was selected as a model drug. From the results of pre-formulation studies, Compritol® HD5 ATO, Gelucire® 48/16, and Capmul® GMO-50 were selected as oil, surfactant and co-surfactant respectively for manufacturing of HME S-SEDDS. Neusilin® US2 was selected as a solid carrier. The design of experiments (response surface methodology) was employed to prepare formulations via a continuous HME process. The formulations were evaluated for emulsifying properties, crystallinity, stability, flow properties and drug release characteristics. The prepared HME S-SEDDS showed excellent flow properties, and the resultant emulsions were stable. The globule size of the optimized formulation was 269.6 nm. The DSC and XRD studies revealed the amorphous nature of the formulation and FTIR studies showed no significant interaction between fenofibrate and excipients. The drug release studies showed significant (p < 0.05) improvement in solubility compared to the pure drug (DE15 = 45.04 for the optimized formulation), as >90% of drug release was observed within 15 min. The stability studies for the optimized formulation were conducted for 3 months at 40 °C/75% RH.

Salt-Resistant, Self-Floatable Fe2O4/Ppy Nanoparticles Decorated Wood Pulp Sponge for Solar-Driven Seawater Desalination

Water scarcity has become a major global challenge in recent years needed to deal with urgently. Solar evaporation has emerged as a renewable energy source and a novel technique for clean water production and wastewater treatment. However, developing a high-performance, environment-friendly, and scalable solar evaporator remains a significant challenge. Herein, we developed a high-performance, self-floatable, environmentally friendly, and single-step manufacturing of a two-dimensional solar steam generator. The developed solar evaporator is composed of facile coating of Fe2O4@PPy nanoparticles (NPs) deposit on low-cost and commercially available super hydrophilic wood pulp sponge which offers a sustainable solution to the ever-growing issues of the energy and water crises. The as-prepared foam exhibits good wettability (zero contact angle), salt-resistance (3 g /180 minutes), low thermal conductivity (0.225 W m−1 K−1), and excellent light absorption of ∼95% due to the omnidirectional porous surface of Fe2O4@PPy NPs. The broadband solar absorption of Fe2O4@PPy solar evaporator is capable to transform into thermal energy (42.3 ˚C) and generate vapors (1.62 kg m-2 h-1) along with 93 % photothermal conversion efficiency under one sun (1 kW m-2). Furthermore, the presented prototype can be directly installed to purify various types of wastewaters with a high rejection ratio of heavy metal ions (nearly 100%). This simple fabrication process with renewable polymer resources and photothermal materials provides fundamental guidance and practical application value toward developing high-performance solar evaporation technologies for remote areas and individuals. Keywords: Fe2O4@PPy, solar steam generation, wood pulp, polypyrrole.

Recent Progress on Ultrathin Metalenses for Flat Optics.

SummaryAs technology advances, electrical devices such as smartphones have become more and more compact, leading to a demand for the continuous miniaturization of optical components. Metalenses, ultrathin flat optical elements composed of metasurfaces consisting of arrays of subwavelength optical antennas, provide a method of meeting those requirements. Moreover, metalenses have many other distinctive advantages including aberration correction, active tunability, and semi-transparency, compared to their conventional refractive and diffractive counterparts. Therefore, over the last decade, great effort has been focused on developing metalenses to investigate and broaden the capabilities of metalenses for integration into future applications. Here, we discuss recent progress on metalenses including their basic design principles and notable characteristics such as aberration correction, tunability, and multifunctionality.

High-Speed Electrodeposition of Textured Monolithic Lithiated Transition Metal Oxide Cathodes for High Energy and Fast Charging Li-Ion Batteries.

Xerion Advanced Battery Corp, founded in 2010, is in the process of commercializing two battery technologies: a) a nanoscale metal foam, produced through electrodeposition, that enables high performance alloy-type active material based electrodes, and b) a single-step electroplating process to manufacture lithiated transition metal oxide (LTMO) cathodes.Xerion’s process benefits from the combined synthesis and electrode formation in just one step – revolutionizing the current commercial slurry-electrode manufacturing process (>20 steps). Certain LTMO’s can be grown as a monolithic structure up to 500 m thick (~ 5 times thicker than state of the art), while simultaneously controlling the crystalline orientation, porosity, surface area and morphology. Ultra-thick textured electrodes significantly decrease the volume, thickness and weight of the resulting battery without compromising run time or power-density. In addition, the deposition process can be applied onto arbitrary shapes giving way to storage solutions that could be integrated as structural and load bearing components leading to low form-factors, ultra-light weight solutions, and new designs. Safety is also improved because conductive agents are not added to the electrode eliminating secondary conductive pathways, which can prevent hard shorts that lead to disastrous thermal run-away events.The transformative electroplating process can utilize low purity feedstocks instead of highly purified lithium hydroxides and lithium carbonates to produce highly pure Li-ion battery cathodes at a fraction of the cost. This feedstock flexibility arises from selective solubility and differences in redox potential of the desired material and the undesired impurity phases. While commercial active material manufacturing requires feedstock purity >99.5%, purities as low as 50% have been demonstrated with Xerion’s molten salt process. As a result, cost modeling has shown that cost to manufacture cells using this process is reduced by up to 50% even when using an expensive cathode chemistry like LiCoO2. The single-step manufacturing method that produces safe batteries with high energy, fast charging, and high-power characteristics, while simultaneously reducing the cost, is possible through the innovative technology being brought to the market by Xerion Advanced Battery Corporation.

Laser induced graphene on phenolic resin and alcohol composite sheet for flexible electronics applications

Harnessing Laser-induced graphene (LIG) on various substrates, its optimization and application for various electronic devices has increased in the recent years. LIG has been reported as an alternative process for the realization of graphene for flexible electronics with excellent strength, conductivity and mechanical robustness. However, in a single-step manufacturing process, the development of a cost-effective, scalable electronic system using LIG is very challenging. In this work, a novel, simple, low-cost, and solid-state approach has been introduced to print and develop LIG-based conductivity traces and patterns. Here, the LIG conductive zones have been formed on various platforms by using phenolic resin (PR). The LIG regions were effectively developed from direct CO2 laser ablation on the PR and polyvinyl alcohol (PR-PVA) composite sheets. This technique makes it possible to easily create highly conductive arrays on various substrates for realizing the components and devices for flexible electronics. By utilizing the augmented power and the speed of CO2 laser, and the ratio of PR-PVA, the optimal conductivity of the formed LIG on PR-PVA sheet has been observed. Unique characteristics of LIG on PR-PVA include simple synthesis process, flexibility, ability to form a thin film with desired conductivity, and cost-effectiveness. The feasibility and viability of the successful LIG on PR-PVA sheet was demonstrated for applications like the capacitive touch sensor and the pressure sensor matrix.

Singlemoded THz guidance in bendable TOPAS suspended-core fiber directly drawn from a 3D printer

Terahertz (THz) technology has witnessed a significant growth in a wide range of applications, including spectroscopy, bio-medical sensing, astronomical and space detection, THz tomography, and non-invasive imaging. Current THz microstructured fibers show a complex fabrication process and their flexibility is severely restricted by the relatively large cross-sections, which turn them into rigid rods. In this paper, we demonstrate a simple and novel method to fabricate low-cost THz microstructured fibers. A cyclic olefin copolymer (TOPAS) suspended-core fiber guiding in the THz is extruded from a structured 3D printer nozzle and directly drawn in a single step process. Spectrograms of broadband THz pulses propagated through different lengths of fiber clearly indicate guidance in the fiber core. Cladding mode stripping allow for the identification of the single mode in the spectrograms and the determination of the average propagation loss (~ 0.11 dB/mm) in the 0.5–1 THz frequency range. This work points towards single step manufacturing of microstructured fibers using a wide variety of materials and geometries using a 3D printer platform.

Laser-induced reduced-graphene-oxide micro-optics patterned by femtosecond laser direct writing

Direct laser writing has emerged as a promising technology for facile and cost-effective single-step manufacturing of laser-induced reduced-graphene-oxide (LIRGO). Since LIRGO’s optical properties can be controlled during photoreduction process, laser-patterned micro-optics can work as light-weight diffractive optical elements over conventional bulk refractive optics. Here, we present ultra-thin diffractive LIRGO micro-optics patterned by femtosecond laser direct writing (FsLDW) with high spatial resolution and wide design flexibility based on the wide parametric tunability of femtosecond pulsed lasers over conventional continuous-wave or long-pulsed lasers. By extensive parametric control of average power (10–120 mW), pulse repetition rate (1–500 kHz) and scan speed (1–100 mm/s) in FsLDW, ultra-thin micro-optics were patterned at three patterning regimes: non-thermal photoreduction regime, thermal photoreduction regime, and ablation regime. The optical performances of Fresnel zone plates (FZP) fabricated under the three regimes were evaluated and compared; the results were 0.7%, 2.4%, and 3.8% for focusing efficiency, 12.2 µm, 13.2 µm, and 12 µm for focal spot size, 1.39 mm, 1.89 mm, and 1.77 mm for depth-of-focus for FZPs designed to 15 mm focal length with 10 concentric rings. This fabrication technique provides wide design flexibility to various planar LIRGO micro-optics for microfluidics, lab-on-a-chip, skin-attachable biomedical imaging, and micro photonic devices.

Hierarchical Composite Meshes of Electrospun PS Microfibers with PA6 Nanofibers for Regenerative Medicine.

One of the most frequently applied polymers in regenerative medicine is polystyrene (PS), which is commonly used as a flat surface and requires surface modifications for cell culture study. Here, hierarchical composite meshes were fabricated via electrospinning PS with nylon 6 (PA6) to obtain enhanced cell proliferation, development, and integration with nondegradable polymer fibers. The biomimetic approach of designed meshes was verified with a scanning electron microscope (SEM) and MTS assay up to 7 days of cell culture. In particular, adding PA6 nanofibers changes the fibroblast attachment to meshes and their development, which can be observed by cell flattening, filopodia formation, and spreading. The proposed single-step manufacturing of meshes controlled the surface properties and roughness of produced composites, allowing governing cell behavior. Within this study, we show the alternative engineering of nondegradable meshes without post-treatment steps, which can be used in various applications in regenerative medicine.

3D printed Sr-containing composite scaffolds: Effect of structural design and material formulation towards new strategies for bone tissue engineering

The use of composite materials, processed as 3D tissue-like scaffolds, has been widely investigated as a promising strategy for bone tissue engineering applications. Also, additive manufacturing technologies such as fused deposition modelling (FDM) have greatly contributed to the manufacture of patient-specific scaffolds with predefined pore structures and intricate geometries. However, conventional FDM techniques require the use of materials exclusively in the form of filaments, which in order to produce composite scaffolds lead to additional costs for the fabrication of precursor filaments as well as multi-step production methods. In this study, we propose the use of an advantageous extrusion-based printing technology, which provides the opportunity to easily co-print biomaterials, starting from their raw forms, and by using a single-step manufacturing and solvent-free process. Poly(e-caprolactone) (PCL), an FDA approved biodegradable material, was used as polymeric matrix while hydroxyapatite (HA) and strontium substituted HA (SrHA), at various contents were introduced as a bioactive reinforcing phase capable of mimicking the mineral phase of natural bone. Three different architectures for each material formulation were designed, and subsequently the effect of composition variations and structural designs was analysed in terms of physico-chemical, mechanical and biological performance. A correlation between architecture and compressive modulus, regardless the formulation tested, was observed demonstrating how the laydown pattern influences the resulting 3D printed scaffolds’ stiffness. Furthermore, in vitro cell culture by using TERT Human Mesenchymal Stromal Cells (hTERT-MSCs) revealed that Sr-containing composite scaffolds showed greater levels of mineralisation and osteogenic potential in comparison to bare PCL and pure HA.

Mechanism-based wear models for plastic injection moulds

Injection moulding is a single-step manufacturing process for plastic parts that require very precise dimensions, geometries and low part roughness (Ra 0.2–0.025 μm). The high cost of moulds (typ. > 100,000 €) and unacceptable wear of their cavities can limit the cost competitiveness of the process. Mould cavity surfaces are deteriorated by different wear mechanisms which may drastically reduce the quality of injection moulded parts, interrupt their production, raise maintenance and repair costs, or delay delivery. Therefore, a better understanding of the wear mechanisms and the main parameters affecting mould wear is needed. In this research, three major failure mechanisms were studied: abrasion and erosion (due to fibre-reinforcements in the plastics), and corrosion (due to gas release from the polymers). Testing protocols were developed for each failure mechanism. Abrasion was simulated with a block-on-plate tribological test, erosion was evaluated in an air-jet erosion tester combined with a gravel-o-meter test, and corrosion was simulated using electrochemical techniques. Three different thermoplastic materials and several mould surface solutions (i.e., mould steel and four alternative surface treatments) were tested. Furthermore, this paper presents an innovative approach to simulate the behaviour of mould and plastic materials at the laboratory scale, in order to minimise the cost associated to mould failures, through mould lifetime prediction. The prediction, with some limitations has been made based on the model generated through laboratory tests, by using a multiparameter design of experiments, where different working conditions (such as pressure or speed) and plastic and mould materials were evaluated. A single best solution was not found to resist all failure mechanisms, but useful recommendations for potential solutions for each failure mechanism were proposed. The TiN coating applied by Physical Vapour Deposition represents a good compromise between wear (abrasive and erosion) and corrosion resistance, especially for fibre reinforced plastics. Ni-PTFE coating is proposed to reduce the friction and improve the corrosion resistance of the mould materials when high wear resistance is not needed, as in the case of non-reinforced plastics.

Springtail-Inspired Triangular Laser-Induced Surface Textures on Metals Using MHz Ultrashort Pulses

Considering the attractive surface functionalities of springtails (Collembola), an attempt at mimicking their cuticular topography on metals is proposed. An efficient single-step manufacturing process has been considered, involving laser-induced periodic surface structures (LIPSS) generated by near-infrared femtosecond laser pulses. By investigating the influence of number of pulses and pulse fluence, extraordinarily uniform triangular structures were fabricated on stainless steel and titanium alloy surfaces, resembling the primary comb-like surface structure of springtails. The laser-textured metallic surfaces exhibited hydrophobic properties and light scattering effects that were considered in this research as a potential in-line process monitoring solution. The possibilities to increase the processing throughput by employing high repetition rates in the MHz-range are also investigated.

Experimental and numerical investigation on the fatigue behaviour of friction stirred channel plates

The friction stir channelling (FSC) process is a technological innovation based on the friction stir fundamentals. To produce friction stirred channel components, a non-consumable tool, similar to that used for friction stir welding (FSW), is used. Friction stir channelling is a single step manufacturing process in which a continuous channel with a specific path is produced in a monolithic metal component. This work discusses the influence of the channel geometry on the bending strength of friction stirred channel aluminium alloy specimens, as well as their fatigue behaviour. Moreover, fatigue analyses using the finite element method were also carried out, considering the channels' geometrical features in order to assess and compare the fatigue lives. The stress intensity factor for different crack lengths was determined using ABAQUS. The fatigue crack growth curve was established according to the Paris Law, and the crack was only allowed to propagate along the materials interface. It was observed that the critical zones are located in the vicinity of the channel corners and found that the fatigue crack propagation period on FSC specimens is very short compared to the crack initiation period. Base and FSW material properties play a major role on fatigue crack propagation simulation. The accuracy of the predicted results increased when considering lower stress amplitudes and by using the FSW material parameters.

Laser-Based Additive Manufacturing of Zirconium

Additive manufacturing of zirconium is attempted using commercial Laser Engineered Net Shaping (LENSTM) technique. A LENSTM-based approach towards processing coatings and bulk parts of zirconium, a reactive metal, aims to minimize the inconvenience of traditional metallurgical practices of handling and processing zirconium-based parts that are particularly suited to small volumes and one-of-a-kind parts. This is a single-step manufacturing approach for obtaining near net shape fabrication of components. In the current research, Zr metal powder was processed in the form of coating on Ti6Al4V alloy substrate. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) as well as phase analysis via X-ray diffraction (XRD) were studied on these coatings. In addition to coatings, bulk parts were also fabricated using LENS™ from Zr metal powders, and measured part accuracy.

Injectable Highly Loaded Cellulose Nanocrystal Fibers and Composites.

Cellulose nanocrystals (CNC)/poly(ethylene oxide) (PEO) composite fibers were successfully produced in situ by injection into a hydrophobic solvent. Using a similar principle, a single step manufacturing method of injectable composites was developed by injection of a CNC solution into a hydrophobic resin. Molecular orientation and deformation of the fibers and composites were obtained using Raman spectroscopy. CNCs were found to be highly aligned along the fiber's axes, as confirmed by 2-fold symmetry of polar plots and second and fourth order orientation parameters. A shift in the position of a characteristic Raman band, initially located at ∼1095 cm-1, corresponding to vibrations of the cellulose backbone polymer chains was followed under tensile deformation. Using this shift, it was possible to estimate the fiber modulus as being ∼33 GPa, which is remarkably high. Stress transfer between the hydrophobic resin and the injected CNC fibers was quantified in this new type of composite using a modified shear-lag theory showing that appreciable reinforcement occurs. Our approach presents a new way to introduce highly loaded CNC fibers in situ into a composite structure.

Single-Step Imprinting of Femtoliter Microwell Arrays Allows Digital Bioassays with Attomolar Limit of Detection.

Bead-based microwell array technology is growing as an ultrasensitive analysis tool as exemplified by the successful commercial applications from Illumina and Quanterix for nucleic acid analysis and ultrasensitive protein measurements, respectively. High-efficiency seeding of magnetic beads is key for these applications and is enhanced by hydrophilic-in-hydrophobic microwell arrays, which are unfortunately often expensive or labor-intensive to manufacture. Here, we demonstrate a new single-step manufacturing approach for imprinting cheap and disposable hydrophilic-in-hydrophobic microwell arrays suitable for digital bioassays. Imprinting of arrays with hydrophilic-in-hydrophobic microwells is made possible using an innovative surface energy replication approach by means of a hydrophobic thiol-ene polymer formulation. In this polymer, hydrophobic-moiety-containing monomers self-assemble at the hydrophobic surface of the imprinting stamp, which results in a hydrophobic replica surface after polymerization. After removing the stamp, microwells with hydrophobic walls and a hydrophilic bottom are obtained. We demonstrate that the hydrophilic-in-hydrophobic imprinted microwell arrays enable successful and efficient self-assembly of individual water droplets and seeding of magnetic beads with loading efficiencies up to 96%. We also demonstrate the suitability of the microwell arrays for the isolation and digital counting of single molecules achieving a limit of detection of 17.4 aM when performing a streptavidin-biotin binding assay as model system. Since this approach is up-scalable through reaction injection molding, we expect it will contribute substantially to the translation of ultrasensitive digital microwell array technology toward diagnostic applications.

A Study on a New 3D Porous Polymer Printing Based on EPP Beads Containing CO2 Gas

We propose a new CO2 gas-based 3D PPP (Porous Polymer Printing) developed based on the Fused Deposition Modeling scheme of Additive Manufacturing. The 3D porous polymer structure was stacked layer by layer, which was a rapid single step manufacturing technique for a multilayer product in single device. A hybrid filament of diameter 1.75 mm was introduced with EPP (Expanded Polypropylene) beads containing CO2 gas. EPP beads, which have several desirable characteristics such as light weight, shock absorption, thermal insulation, heat resistance, weather resistance, oil resistance, and chemical resistance, were also subject to various process conditions such as EPP type, laminate thickness, printing speed and nozzle temperature. In this paper, three types of EPP beads with expansion ratios of 15, 30 and 40% were investigated. We found the experimentally optimal process conditions of a new CO2 gas-based 3D PPP method and finally demonstrated a simple 3D structure. In the future, a faster production and the mechanical shock absorption effect will be studied and tested for application in the automobile industry.

Single-step manufacturing of curved polypropylene composites using a unique sheet consolidation method

Many techniques have been developed over the past few decades to manufacture curved fibre reinforced thermoplastic composites. Long-fibre composite parts have been mostly manufactured by either compression moulding or thermoforming in two or more steps. No effort has been put into single-step manufacturing of long fibre curved thermoplastic composite parts. This work develops a manufacturing plan that has the ability to produce fairly strong curved thermoplastic composites in a single step. The production of composites according to this plan is expected to be significantly cheaper than the composites produced by compression moulding or thermoforming. In this research, curved composites were manufactured from flax reinforcements and polypropylene sheets using a unique manufacturing cycle, where the composites were formed and consolidated simultaneously. The optimum processing parameters and the fibre volume fraction were found to manufacture curved flax reinforced polypropylene composites with acceptable tensile and shear strengths. An experimental setup was used to monitor and record the applied vacuum pressure and temperature during the experiments. Shear and tensile strength of the manufactured composites was found. The consolidation quality of the manufactured composites was assessed by examining the composite specimens’ cross-sections under an optical microscope. The results showed that the tensile and shear strengths of the manufactured composites were dependent on the fibre volume fraction, transverse permeability of the fibre reinforcement and also the magnitude and method of application of compaction pressure. There were optimum fibre volume fractions with respect to tensile and shear strengths for each of the three fibre reinforcements used in this research. The shear and tensile strengths of the composites produced in this research are comparable to compression moulded or thermoformed parts.