Uniform Coatings Research Articles

Relationship between deposition techniques and nanoparticle dispersions for flexible and printed electronics

Reverse micelles composed of polystyrene-b-poly(2-vinylpyiridine) have been used to synthesize nanoparticles composed of a wide range of materials, including metals, metal oxides, dielectrics, semiconductors perovskites, and core–shell nanoparticles. In this contribution, we examine the effect of deposition parameters on two-dimensional nanoparticle arrangements from colloidal solutions created using spin coating, dip coating, slot-die coating, and electrospray deposition. Despite the importance of achieving uniform coatings of ordered arrays of colloidal particles, previous studies have not thoroughly addressed this challenge. We show that the adjustability of interparticle distance depends on the deposition technique used and only occurs within the stable defect-free operating window of the deposition parameters. Establishing the specific operating window for each technique for a model system, we propose general guidelines that can be used for ensuring uniform coatings regardless of precursor loading and provide a guide for adjusting the deposition conditions when coating defects occur. We introduces a novel application of ellipsometry to evaluate interparticle spacing in nanoparticle arrays, enhancing our ability to assess film uniformity, allowing for quick and easy tuning of nanoparticle dispersion. Comparisons between spin, dip, and slot-die coating techniques reveal insights into the correlation between interparticle spacing and ordering, highlighting the importance of fitting relationships for various coating samples. This comprehensive comparison and discussion provide a roadmap for future research, outlining current challenges and trends and offering insights into achievable spacings and ordering in coating processes. This allows the classification of various deposition techniques with respect to their suitability for tailored applications.

Instruments and methods for coating of wavelength-shifting materials used for noble liquid technology

The use of wavelength-shifting coatings is of primary interest in the area of liquified noble gases detectors. Argon and xenon are used as active medium in the neutrino physics and dark matter experiments, because charged particles crossing the noble liquid volume produce excitation and ionization followed by recombination and both the processes lead to the emission of VUV light. Noble liquid scintillation light emitted in the VUV range needs to be converted to be detected by conventional photosensors. Wavelength-shifting materials, such as TetraPhenyl-Butadiene and p-TerPhenyl, are used for this conversion to the visible range. The wavelength-shifters are particularly important in the case of large area detectors since only a fraction of the surface can be instrumented. To this purpose dedicated set-ups have been built and specific techniques have been adopted to produce and characterize very uniform wavelength-shifting coatings on highly reflecting material substrates, optical filters and optical guides. Some type of the facilities used to this task, with particular attention to the vacuum deposition systems, will be described, operations for production of the coatings will be reported, methods for the characterization of the samples will be briefly presented.

First photo evidence of Siberian Weasel Mustela sibirica Pallas, 1773 (Mammalia: Carnivora: Mustelidae) in Gaurishankar Conservation Area, Nepal

Five photographs of Siberian Weasel were captured by camera traps in two locations at an elevation of 2,840-3,200 m. in Gaurishankar Conservation Area. The species was identified based on its uniform yellowish-brown coat, the presence of a black mask that surrounded its eyes and the white chin, which are key characteristics that distinguishes it from other weasel species. This is the first confirmation of the presence of Siberian Weasel in Gaurishankar Conservation Area, Nepal. Based on present and previous confirmed records, a distribution map of the species has been updated for Nepal.

Inkjet Printing Photoresist with Ultralow Viscosity on Silicon Wafers for Uniform Coating.

Inkjet printing is introduced into the photoresist coating process for uniform photoresist film formation on silicon wafers with the in-house inkjet experimental prototype. The optimization of a dual negative voltage waveform is proposed to achieve stable droplet jetting for the ultralow viscosity (0.71 mPa·s) photoresist with a 1:10 dilution ratio employed in the semiconductor packaging processes. Moreover, the maximum droplet jetting velocity can reach 9.51 m/s, and the droplet volume is controlled at ∼6.5 pL with excellent droplet concentration. The uniform film of the AZ P4620 photoresist is coated on silicon wafers by quantitatively exploring and optimizing the printhead driving frequency and movement velocity utilizing the droplet deposition model and experimental analysis. Results show that the optimal inkjet parameters with 5 kHz in jetting frequency and 6 mm/s in motion velocity can obtain a film evenness index of 4.81% with the thickness of 0.945 μm, which exhibits a more uniform photoresist film than the spray coating method. The study not only expands the application of the inkjet printing technique but also offers an alternative for photoresist coating in the photolithography process.

Polydimethylsiloxane Surface Modification of Microfluidic Devices for Blood Plasma Separation.

Over the last decade, researchers have developed a variety of new analytical and clinical diagnostic devices. These devices are predominantly based on microfluidic technologies, where biological samples can be processed and manipulated for the collection and detection of important biomolecules. Polydimethylsiloxane (PDMS) is the most commonly used material in the fabrication of these microfluidic devices. However, it has a hydrophobic nature (contact angle with water of 110°), leading to poor wetting behavior and issues related to the mixing of fluids, difficulties in obtaining uniform coatings, and reduced efficiency in processes such as plasma separation and molecule detection (protein adsorption). This work aimed to consider the fabrication aspects of PDMS microfluidic devices for biological applications, such as surface modification methods. Therefore, we studied and characterized two methods for obtaining hydrophilic PDMS surfaces: surface modification by bulk mixture and the surface immersion method. To modify the PDMS surface properties, three different surfactants were used in both methods (Pluronic® F127, polyethylene glycol (PEG), and polyethylene oxide (PEO)) at different percentages. Water contact angle (WCA) measurements were performed to evaluate the surface wettability. Additionally, capillary flow studies were performed with microchannel molds, which were produced using stereolithography combined with PDMS double casting and replica molding procedures. A PDMS microfluidic device for blood plasma separation was also fabricated by soft lithography with PDMS modified by PEO surfactant at 2.5% (v/v), which proved to be the best method for making the PDMS hydrophilic, as the WCA was lower than 50° for several days without compromising the PDMS's optical properties. Thus, this study indicates that PDMS surface modification shows great potential for enhancing blood plasma separation efficiency in microfluidic devices, as it facilitates fluid flow, reduces cell aggregations and the trapping of air bubbles, and achieves higher levels of sample purity.

Nanotechnology in the Fabrication of Advanced Paints and Coatings: Dispersion and Stabilization Mechanisms for Enhanced Performance

AbstractThis review comprehensively analyzes the challenge of dispersing and stabilizing of various common nanomaterials (NMs), including TiO₂, SiO₂, Ag, ZnO, graphene, carbon nanotubes (CNTs) and some others, in paints and coatings. It delves into the critical factors influencing dispersion, such as nanoparticle size, shape, concentration, and their distribution within the coating matrix.The review encompasses all stages of dispersion methods, including wetting, separation techniques, and stabilization. Regarding stabilization, both chemical and physical stabilization methods are discussed, along with their mechanisms, involving surface modification or functionalization of NMs, particularly tailored for aqueous and solvent‐based coatings and common resins (Acrylic, Urethane, Epoxy, Alkyd, etc.). Furthermore, common blending methods to fabricate uniform paints, coatings, and nanocomposites (NCPs) are examined. By providing a comprehensive understanding of the mechanisms governing NM dispersion and stabilization, this review facilitates the selection of appropriate surface modifications based on the specific resins or solvents, thereby enabling the fabrication of high‐performance paints and coatings. In summary, this review elucidates the essence of addressing the challenges associated with NM dispersion and stabilization, outlines methodologies employed, discusses findings regarding their effects on coating properties, and recommends tailored approaches for fabricating high‐performance paints and coatings.

Capillarity-assisted assembly of composite fibers to enable highly conductive fabrics for electromagnetic interference shielding

Poor adhesion between silver nanomaterials and substrates seriously restricts the development of electronic composite devices. In this work, flexible and conductive silver nanowires/fibroin/degummed silk (AgNWs/fibroin/dSF) composite fibers with high adhesion and conductivity via capillarity-assisted assembly for electromagnetic interference (EMI) shielding are designed and fabricated by a facile and scalable all-solution dip-coating method. The nanocomposite fiber possesses high conductivity with a resistance of 8.8 Ω/cm at a low AgNWs/fibroin loading of 19.3 wt%. The assistance of the capillary force in the fiber highly increases the mass of deposited AgNWs. Furthermore, the AgNWs show high adhesion on the fibers in the tape-peel test. The enhanced deposition factors and mechanisms are detailly investigated. Moreover, the composite fibers are further woven into a soft and flexible fabric. The composite fabric shows an absorption-dominated EMI shielding performance with an efficient shielding effectiveness of 38 dB. The capillarity-assisted assembly is an attractive procedure for constructing high-conductive and uniform coatings for a wide application.

A novel biofunctional TaCu coating on Ti6Al4V by CVD method

Although Ti6Al4V alloy has been widely used in the orthopedic implants, their problems of toxic metal ions dissolution and the lack of biological activity still has negative effects on the clinic outcome. To solve these problems, a novel biofunctional Cu bearing Ta coating on Ti6Al4V alloy surface by CVD was proposed. In this study, by Ta/Cu co-deposition, the uniform and compact TaCu coatings with different Cu contents were successfully prepared for the first time. It was found that the Ta-1.2Cu coating had excellent antibacterial ability, and the antibacterial rate against both E. coli and S. aureus reached 99.9 %. Additionally, owing to Al and V toxic elements being restricted in the matrix and the excellent biological activity of Ta, the TaCu coatings on Ti6Al4V alloy simultaneously eliminated the toxicity of metal ions and acquired anti-infection function.

One step synthesis of durable slippery, oil/water selective, corrosion-resistant silicone coatings with grafted flexible sidechains

Slippery liquid-infused porous surfaces (SLIPSs) based on polymer matrices impregnated with liquid lubricants are multifunctional and provide a wide range of useful properties such as low adhesion of water and other liquids, selectivity, high corrosion resistance, etc. However, these properties vanish quickly due to the gradual depletion of lubricant from the matrix. This issue could be resolved by attaching lubricant molecules to the matrix as flexible, liquid-like sidechains. In the present work, thin silicone films with grafted sidechains are fabricated. The uniform coatings are obtained in “eco-friendly” pressurized (subcritical) CO2 on smooth silicon wafers as well as on rough porous substrates such as carbon aerogels. The possibility of applying films by the traditional dip-coating method is also demonstrated on titanium slides. The coatings demonstrate low sliding angles for water and water/alcohol solution droplets. Coated aerogels preserve high porosity. It is demonstrated that initially hydrophilic aerogels become highly hydrophobic after coating and selectively absorb oil from water/oil mixtures. The tests of obtained coatings on titanium substrates demonstrate a significant increase in corrosion resistance. The proposed technique has a wide range of potential applications where such slippery coatings should be applied on complex rough substrates: from filtration materials production to textile finishing.

Controlled micro-scale ink droplet spreading on cotton fabrics via cellulose-based coatings for greener textile inkjet printing

Inkjet printing of cotton fabric is considered a cleaner, efficient and revolutionary technology in textile coloration industry. However, due to the good hydrophilicity of cotton fibers, ink droplet spreading was difficult to be prevented, causing the problems of poor image resolution, low dye utilization efficiency and reduced product quality. Hence, in this study, cellulose-based coatings were fabricated on the cotton surface to adjust the surface hydrophilicity and prevent ink droplet spreading. Results showed that, cellulose derivatives like hydroxypropyl cellulose (CMHPC) and hydroxyethyl methyl cellulose (HEMC) could form continuous and uniform cellulose film coatings on fiber surface. Because there are fewer hydrophilic side groups in HEMC structure, the hydrophilicity of cotton fabric and the ink spreading was effectively controlled. From microscope observation, the spreading lengths of a single droplet were significantly decreased by HEMC from 276.27 to 66.95 μm. The K/S values representing color depth were improved from 9.44 to 19.41. Furthermore, industrial application was conducted to verify the laboratory results, showing that higher image quality was obtained in practical application using HEMC. This work provides a more potential and greener application of cellulose-based coatings to promote the development of textile inkjet printing.

Construction of Uniform LiF Coating Layers for Stable High-Voltage LiCoO2 Cathodes in Lithium-Ion Batteries.

Stabilizing LiCoO2 (LCO) at 4.5 V rather than the common 4.2 V is important for the high specific capacity. In this study, we developed a simple and efficient way to improve the stability of LiCoO2 at high voltages. After a simple sol-gel method, we introduced trifluoroacetic acid (TA) to the surface of LCO via an afterwards calcination. Meanwhile, the TA reacted with residual lithium on the surface of LCO, further leading to the formation of uniform LiF nanoshells. The LiF nanoshells could effectively restrict the interfacial side reaction, hinder the transition metal dissolution and thus achieve a stable cathode-electrolyte interface at high working-voltages. As a result, the LCO@LiF demonstrated a much superior cycling stability with a capacity retention ratio of 83.54% after 100 cycles compared with the bare ones (43.3% for capacity retention), as well as high rate performances. Notably, LiF coating layers endow LCO with excellent high-temperature performances and outstanding full-cell performances. This work provides a simple and effective way to prepare stable LCO materials working at a high voltage.

Plasma-chemical synthesis of carbide-based vacuum-plasma functional coatings and study of tribological characteristics of friction pairs

The work is devoted to the search for new materials with high functional characteristics using the Avinit vacuum-plasma technologies developed by us, based on the complex use of coating methods (plasma-chemical CVD, vacuum-plasma PVD (vacuum-arc, magnetron), processes of ion saturation and ion surface treatment), stimulated by non-equilibrium low-temperature plasma.Processes of controlled plasma-chemical synthesis of the formation of multicomponent coatings in "metal-carbon" systems – Avinit coating (TiC, MoC) using vacuum-arc sources of ionized atomic fluxes of titanium and molybdenum in an argon-benzene plasma environment were developed and their characteristics were studied depending on their conditions formation.Metallographic studies confirm the possibility of low-temperature application of high-quality wear-resistant high-hard "metal-carbon" coatings with a hardness of 18,000-30,000 MPa, while ensuring good adhesion to the substrate materials (steel DIN 1.2379) without reducing strength and without deteriorating the cleanliness class of the original surface.The conducted tribological tests using the "cube-roller" scheme reveal high tribological characteristics of steel DIN 1.2379 tribopairs with developed coatings and testify to the promisingness of the developed multi-component multilayer coatings Avinit (Ti-C, MoS) for increasing wear resistance and reducing the coefficient of sliding friction in friction nodes.The developed plasma-chemical vacuum-plasma coatings are applied to mock-up samples of the working compressor blades of the GTE of aircraft engines. Proven modes allow to get high-quality, uniform coatings with high adhesion.This gives reason to consider the developed process as an alternative for expanding the range of new Avinit vacuum-plasma erosion-resistant coatings and developing structures of anti-friction wear-resistant coatings to increase the performance of friction pairs in "coating-steel" and "coating-coating" systems.

Functionalization of modified titanium by plasma electrolytic oxidation with antibiotic and cell adhesion promoters to improve osseointegration processes

Osseointegration of medical metals such as titanium (Ti) can be improved by inducing surface roughness. Plasma electrolytic oxidation (PEO) is a promising technique not only for controlling parameters such as porous size and thickness reproducibility but also producing uniform coatings. This study focused on proposing a cocktail of molecules consisting of the broad-spectrum antibiotic Gentamicin, RGD and GRGDSP adhesion peptides, and the bone growth factor BMP-4 to prevent microbial colonization and promote bone cell integration. For this, commercially pure (c.p) Ti and Ti6Al4V were anodized by PEO and then, a systematic evaluation of the immobilization and effect of each element in the biological performance was evaluated. The antibacterial effect against Klebsiella pneumoniae, Staphylococcus aureus and Pseudomonas aeruginosa strains was successfully observed. In addition, the osteoblast growth and mineralization were observed in the studied formulations. In conclusion, a formulation composed of gentamicin, growth factor BMP-4, and peptides either RGD or GRGDSP is proposed to immobilize the surface of implants for orthopedic and dental implant application.

Protective Nanosheet Coatings for Thiophosphate‐Based All‐Solid‐State Batteries

AbstractSuperionic sulfide solid electrolytes (SEs) are of considerable interest for application in solid‐state batteries, but suffer from limited stability. When in combination with state‐of‐the‐art cathode active materials (CAMs), severe degradation at the CAM/SE interface occurs during electrochemical cycling. To improve upon the interfacial stability, inert coatings can be applied to the CAM particles, with the goal of preventing direct contact to the SE. In this study, different methods of depositing coatings, including hexagonal boron nitride, tungsten sulfide and exfoliated ((CH3(CH2)3)4N)4Nb6O17, in the form of nanosheets onto the free surface of a Ni‐rich LiNixCoyMnzO2 (NCM) CAM are examined and compared with one another. While dry coating is shown to produce relatively uniform coatings (good surface coverage), the secondary particle morphology of the NCM makes ball milling as a mechanical deposition method less attractive. In contrast, deposition from dispersions in organic solvents yields protective coatings with a lower degree of surface coverage. The different materials are electrochemically tested in liquid‐ and solid‐electrolyte‐based lithium‐ion batteries. A stabilizing effect from nanosheet coating is only observed for the cells with lithium thiophosphate SE.

Slot‐Die Coating for Scalable Fabrication of Perovskite Solar Cells and Modules

AbstractSolution‐coating processes are promising methods to form active layers with low‐cost input in the industrial development of perovskite solar devices. Among available coating processes, of particular interest are those capable of producing uniform coatings with small defect distribution over large areas at high speeds, referred to as scalable methods. Slot‐die coating is one of these methods. It involves the meniscus coating of liquids or solutions over a static or moving substrate. This review discusses recent advances in slot‐die coating of active layers used in perovskite solar cells (PSCs) and modules (PSMs). Various strategies to control ink spreading over substrates, wet film drying, and post‐coating crystallization of light‐absorbing perovskite layer are outlined along with different approaches and materials used in post‐deposition defects healing. Then, commonly used solvents for perovskite ink formulation are analyzed based on their specific rheology and potential effect on human health and equipment safety. Also, precursor materials, solvents, and strategies to obtain desirable properties and morphology in the slot‐die coating of charge‐transporting layers are discussed. Lastly, an analysis of the performance of slot‐die coated perovskite solar mini‐modules and future perspectives on this topic conclude this review.

Electrochemically produced films based on individual porphyrins and bimetallic composites: Morphology and electrocatalytic properties in the reaction of oxygen electroreduction

In this work, we obtained polyporphyrin films based on Fe(III)Cl-5,10,15,20-tetrakis(4-pyridyl)porphyrin and Mn(III)acetate-5,10,15,20-tetrakis(4-pyridyl)porphyrin and composite films on their basis by electrooxidation-induced electrochemical polymerization. The obtained films produced uniform coatings. Spectral analysis showed that the composite films were enriched with iron complexes. Comparative analysis of the prepared films demonstrated differences between the morphologies of the composite film and films of individual metal complexes. The oxygen electroreduction process on the obtained materials proceeded at more positive values than that on carbositall. The effective number of transferred electrons demonstrated that replacing catalysts based on individual porphyrins with the bimetallic composite changed the process mechanism: while the four-electron mechanism competed with subsequent two-electron reactions on the Fe(III)Cl-5,10,15,20-tetrakis(4-pyridyl)porphyrin and Mn(III)acetate-5,10,15,20-tetrakis(4-pyridyl)porphyrin films, on the bimetallic composite the process mainly represented a four-electron reaction.

Precursor design and cascade mechanism of RuO2·xH2O atomic layer deposition

As the unique nanofabrication technique, atomic layer deposition (ALD) can be used to deposit high-quality, uniform, and conformal nanoparticle coatings. Ru and its oxides (RuOx) are important materials in the fields of microelectronics and catalysis. In this work, the reaction of Ru precursors with different ligands on the hydroxylated surfaces were explored. The elimination of the pyrrolyl (Py) ligand is easier than that of the cyclopentadienyl (Py) ligand on the hydroxylated surface. The reaction involved in RuO2·xH2O ALD using RuPy2 and H2O as precursors was further investigated. During the RuPy2 reaction, the pyrrolyl ligand is eliminated by the substitution reaction with a surface hydroxyl group. However, the desorption of the pyrrole molecule is difficult due to the strong adsorption between the pyrrole molecule and Ru surface. During the H2O reaction, the H2O molecules further help the elimination of pyrrolyl ligands from the surface and the dissociative desorption of pyrrole molecules This unique reaction mechanism involved in the ALD of RuO2 with the assistance of H2O can be termed new cascade mechanism. These findings provide theoretical guidance for precursor design and ALD growth of metal oxides.

Experimental investigation on the wear characteristics of TiC-Co composite coating deposited on AZ91D Mg alloy substrate by plasma transferred arc (PTA) welding process

Abstract In this investigation, a plasma transferred arc (PTA) cladding process was employed to deposit TiC-Co composite coatings on substrate of AZ91D magnesium (Mg) alloy. The morphology and phases of the recently produced composite coatings were examined using scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The microhardness and wear rate were evaluated by Vickers microhardness tester and pin-on-disc wear and friction test apparatus at the room temperature respectively. The results demonstrate that dense, uniform, and crack free coatings, with good metallurgical bonding to the AZ91D Mg alloy substrate were formed. The most of the phases present in composite coatings were TiC, Mg, CoTi, α-Co, AlCo, Al3Ti, and Co3C. The maximum average micro-hardness of TiC-Co composite coating was found to be about 1743 HV, which depends on the PTA currents. Whereas, average micro-hardness of the AZ91D Mg alloy substrate was 65 HV. This indicates that the coated layer produced increase in hardness about 27 times of substrate hardness. The cladding layer exhibited a wear rate of 4.94×10-8 g/N-m, whereas the wear rate of the AZ91D Mg alloy substrate was 58×10-8 g/N-m. This indicates that the wear resistance of cladding layer was 12 times higher as compared to AZ91D Mg alloy substrate. The enhanced micro-hardness and wear resistance of TiC-Co composite coating can be attributed due to the formation of ceramic and intermetallic compounds, unveiling its superiority over the AZ91D substrate.

Everolimus-encapsulation in Pluronic P123 self-assembled micelles as drug delivery systems for drug-coated balloons

Drug-coated balloons (DCBs) are effective tools for cardiovascular interventions, ensuring uniform drug delivery to occluded arteries. This research investigates the potential of Pluronic P123 (P123), a micelle-forming polymer, to solubilize and release Everolimus (EVE) from DCBs. Furthermore, it seeks to understand how the ratio of P123 to EVE affects release rates and micelle formation under physiological conditions. We tested three P123 to EVE ratios: 90:10, 75:25, and 50:50. Microscopy revealed that increasing EVE proportions resulted in more uniform coatings. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed the successful incorporation of EVE into the P123 matrix without altering its chemical properties. Differential scanning calorimetry (DSC) studies showed that EVE incorporation affected the crystalline structure of P123, leading to more uniform coatings. In vitro release studies showed that all formulations had <1% drug loss in the first minute (the tracking phase); furthermore, the 90:10 ratio exhibited optimal drug release in the following 3 min, corresponding to the deployment phase in DCB angioplasty. Analysis of micelle loading capacity (LC), encapsulation efficiency (EE), size, and structure indicated an increase in both LC and EE with higher EVE content and a corresponding enlargement in micelle size. Given these findings, the optimized formula provided a consistent coating on commercial balloons, highlighting the potential of using P123 for DCB drug coating and release.

An integrated design strategy coupling additive manufacturing and matrix-assisted pulsed laser evaporation (MAPLE) towards the development of a new concept 3D scaffold with improved properties for tissue regeneration.

Bioinspired strategies for scaffold design and optimization were improved by the introduction of Additive Manufacturing (AM), thus allowing for replicating and reproducing complex shapes and structures in a reliable manner, adopting different kinds of polymeric and nanocomposite materials properly combined according to the features of the natural host tissues. Benefiting from recent findings in AM, a Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique was employed for obtaining graphene-like material (GL) uniform coatings on 3D scaffolds for tissue repair strategies, towards the development of a new concept 3D scaffold with controlled morphological/architectural and surface features and mechanical and biological properties. The effect of the material-design combination through an integrated technological approach (i.e., MAPLE deposition of GL on 3D AM PCL scaffolds) was assessed through scanning electron microscopy, atomic force microscopy, contact angle measurements, mechanical measurements and biological analyses (cell viability assay and alkaline phosphatase activity) in conjunction with confocal laser scanning microscopy. The differentiation of hMSCs towards the osteoblast phenotype was also investigated analysing the gene expression profile. The obtained findings provided a further insight into the development of improved strategies for the functionalization or combination of GL with other materials and 3D structures in a hybrid fashion for ensuring a tighter adhesion onto the substrates, improving cell fate over time, without negatively altering the mechanical properties and behaviour of the neat constructs. In particular, the results provided interesting information, making 3D AM GL-coated scaffolds potential candidates for bone tissue engineering.