Juan P. Hinestroza

Nanotechnology in Textiles

Increasing customer demand for durable and functional apparel manufactured in a sustainable manner has created an opportunity for nanomaterials to be integrated into textile substrates. Nanomoieties can induce stain repellence, wrinkle-freeness, static elimination, and electrical conductivity to fibers without compromising their comfort and flexibility. Nanomaterials also offer a wider application potential to create connected garments that can sense and respond to external stimuli via electrical, color, or physiological signals. This review discusses electronic and photonic nanotechnologies that are integrated with textiles and shows their applications in displays, sensing, and drug release within the context of performance, durability, and connectivity. Risk factors including nanotoxicity, nanomaterial release during washing, and environmental impact of nanotextiles based on life cycle assessments have been evaluated. This review also provides an analysis of nanotechnology consolidation in the textiles market to evaluate global trends and patent coverage, supplemented by case studies of commercial products. Perceived limitations of nanotechnology in the textile industry and future directions are identified.

Metal Nanoparticles on Natural Cellulose Fibers: Electrostatic Assembly and In Situ Synthesis

The conformal deposition of metal nanoparticles (Au, Pd, and Pt) onto natural cellulose fibers using two chemical strategies is reported. The driven mechanism responsible for the high surface coverage of the substrates was identified as the electrostatic interactions between the positively charged cellulose and the either negatively charged nanoparticles or negative metal complex ions. The natural cellulose fibers were rendered cationic by grafting ammonium ions, using an epoxy substitution reaction, to the abundant hydroxyl groups present in cellulose molecules. The first method involved the electrostatic assembly of citrate-stabilized metal nanoparticles directly onto the cationic surfaces of cellulose. The second method involved the adsorption of negative metal complex ions onto the cationic cellulose followed by a reduction reaction. The attained metal nanoparticles bound with cellulose fibers were characterized by electron microscopy (TEM and SEM) and energy-dispersive X-ray spectroscopy (EDX). Both pathways generated metal nanoparticles with high packing densities on the cellulose substrates even when very dilute solutions of metal colloids or metal salts were used. Achieving high surface coverage with low-concentration precursor solutions may open an avenue for the production of flexible catalytic mantles or highly functionalized textile substrates.

Layer-by-layer deposition of polyelectrolyte nanolayers on natural fibres: cotton.

The layer-by-layer (LbL) deposition of poly(sodium 4-styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) over cotton fibres is reported. Cotton fibres offer unique challenges to the deposition of nanolayers because of their unique cross section as well as the chemical heterogeneity of their surface. Cationic cotton substrates were produced by using 2,3-epoxypropyltrimethylammonium chloride. Attenuated total reflectance FTIR, x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) were used to validate the presence of the nanolayers as well as to corroborate their self-organized structure. TEM images indicated conformal and uniform coating of the cotton fibres. XPS spectral data were found to be in quantitative agreement with previous published work that studied the LbL deposition of PSS and PAH over synthetic substrates.

Deposition of silver nanoparticles on cellulosic fibers via stabilization of carboxymethyl groups

The stabilizing role of carboxymethyl groups on the conformal deposition of Ag NPs over cellulosic fibers was elucidated while developing a method for the deposition of silver nanoparticles (NPs) on cellulose acetate (CA), cellulose and partially carboxymethylated cellulose (CMC) electrospun fibers. CMC fibers were prepared through judicious anionization of deacetylated cellulose acetate fibers. Ag NPs were chemically reduced from silver nitrate using sodium borohydride and further stabilized using citrate. Ag NPs were directly deposited onto CA, cellulose and CMC electrospun fibers at pH conditions ranging from 2.5 to 9.0. The resulting composites of Ag/fiber were characterized by field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX). The results revealed that the amount of Ag agglomerates and NPs deposited on CMC fibers was higher than that deposited on cellulose fibers at similar pH conditions, and that barely any Ag agglomerates or NPs were deposited on the CA fibers. These results implied that functional groups on the cellulose backbone played two important roles in the deposition of NPs as follows: (1) Hydrogen bonding was the main driving force for agglomeration of NPs when the medium pH was below 4.4, which corresponds to the pKa of carboxylic acid groups; (2) Carboxymethyl groups could replace citrate groups as stabilizers allowing the fabrication of a uniform and evenly distributed Ag NPs layer over CMC fibers at higher pH values. This report also highlights the importance of the substrate’s surface charge and that of the pH of the medium used, on the deposition of NPs. The composite of Ag NPs on CMC electrospun fibers appears to be a promising candidate for wound dressing applications due to its superior antibacterial properties originated by the uniform and even distribution of Ag NPs on the surface of the fibers and the wound healing aptness of the CMC fibers.

Smart textiles: Tough cotton

Cotton is an important raw material for producing soft textiles and clothing. Recent discoveries in functionalizing cotton fibres with nanotubes may offer a new line of tough, wearable, smart and interactive garments.

Adsorption and Association of a Symmetric PEO-PPO-PEO Triblock Copolymer on Polypropylene, Polyethylene, and Cellulose Surfaces

The association of a symmetric polyoxyethylene-polyoxypropylene-polyoxyethylene (PEO(19)-PPO(29)-PEO(19)) triblock copolymer adsorbed from aqueous solutions onto polypropylene (PP), polyethylene (PE), and cellulose surfaces was probed using Atomic Force Microscopy (AFM). Significant morphological differences between the polyolefin substrates (PP and PE) and the cellulose surfaces were observed after immersion of the films in the PEO(19)-PPO(29)-PEO(19) solutions. When the samples were scanned, while immersed in solutions of the triblock copolymer, it was revealed that the structures adsorbed on the polyolefin surfaces were smoothed by the adsorbed PEO(19)-PPO(29)-PEO(19). In contrast, those structures on the hydrophilic cellulose surfaces were sharpened. These observations were related to the roughness of the substrate and the energy of interaction between the surfaces and the PEO and PPO polymer segments. The interaction energy between each of the blocks and the surface was calculated using molecular dynamics simulations. It is speculated that the associative structures amply reported in aqueous solution at concentrations above the critical micelle concentration, CMC, are not necessarily preserved upon adsorption; instead, it appears that molecular arrangements of the anchor-buoy type and hemimicelles prevail. The reported data suggests that the roughness of the surface, as well as its degree of hydrophobicity, have a large influence on the nature of the resulting adsorbed layer. The reported observations are valuable in explaining the behavior of finishing additives and lubricants commonly used in textile and fiber processing, as well as the effect of the morphology of the boundary layers on friction and wear, especially in the case of symmetric triblock copolymers, which are commonly used as antifriction, antiwear additives.

In situ synthesis of a Cu-BTC metal–organic framework (MOF 199) onto cellulosic fibrous substrates: cotton

A mechanism for chemical attachment and growth of a Cu-BTC Metal–Organic Framework, also known as MOF-199 or HKUST-1, onto cellulosic substrates is reported. Four different experimental procedures were attempted in order to elucidate the role of carboxylate groups on the anionic cellulose’s surface. The order of addition of Cu(OAc)2—copper acetate, BTH3, 1,3,5-benzenetricarboxylic acid and TEA—Triethylamine was found to be a critical factor for the attachment and growth of the MOF-199 crystals onto anionic cellulose. The presence of MOF-199 crystals was probed using XRD and XPS spectra and a strong chemical interaction to the carboxymethylated cellulose fibers was confirmed by intense and vigorous washing of the specimens with water, DMF and methanol. Based on the recognized ability of MOF-199 to capture gases and toxic chemicals, combined with the availability of cellulose-based fibrous materials, the described procedure provides the basis for future fabrication of functionalized fibers and active filtration media.

Biocomposite of nanostructured MnO2 and fique fibers for efficient dye degradation

We report on the in situ synthesis of nanostructured MnO2 onto natural fique fibers. The fiber surface was rendered positive by exposure to alkaline conditions, and permanganate anions (MnO4−) were embedded onto the resultant alkali cellulose via coulombic interactions. An ultrasound-assisted procedure was used to reduce MnO4− and yield MnO2 nanoparticles (NPs). UV-Vis diffuse reflectance was used to assess the influence of the precursor concentration, loading and reduction times on the synthesis of the nanostructured MnO2. FESEM provided direct evidence that MnO2 NPs and aggregates could be formed on the fibers surface. The catalytic activity of the new bionanocomposite was tested for the removal of indigo carmine dye in water samples. The MnO2–fique fiber bionanocomposite was able to remove up to 98% of the colour present in the contaminated water samples in less than 5 minutes. Mass spectrometry was used to determine the degradation route of the dye. Additionally, we found that the bionanocomposite can be reused with no effect on the dye degradation efficiency. The reported procedure provides a new route for the development of biodegradable and easy to synthesize composite materials capable of efficiently degrading pollutants found in industrial effluents.

Effect of poly(ethylene oxide)-silane graft molecular weight on the colloidal properties of iron oxide nanoparticles for biomedical applications

The size, charge, and stability of colloidal suspensions of magnetic nanoparticles with narrow size distribution and grafted with poly(ethylene glycol)-silane of different molecular weights were studied in water, biological buffers, and cell culture media. X-ray photoelectron spectroscopy provided information on the chemical nature of the nanoparticle surface, indicating the particle surfaces consisted of a mixture of amine groups and grafted polymer. The results indicate that the exposure of the amine groups on the surface decreased as the molecular weight of the polymer increased. The hydrodynamic diameters correlated with PEG graft molecular weight and were in agreement with a distributed density model for the thickness of a polymer shell end-grafted to a particle core. This indicates that the particles obtained consist of single iron oxide cores coated with a polymer brush. Particle surface charge and hydrodynamic diameter were measured as a function of pH, ionic strength, and in biological buffers and cell culture media. DLVO theory was used to analyze the particle stability considering electrostatic, magnetic, steric, and van der Waals interactions. Experimental results and colloidal stability theory indicated that stability changes from electrostatically mediated for a graft molecular weight of 750 g/mol to sterically mediated at molecular weights of 1000 g/mol and above. These results indicate that a graft molecular weight above 1000 g/mol is needed to produce particles that are stable in a wide range of pH and ionic strength, and in cell culture media.

Direct measurement of fluid velocity in an electrospinning jet using particle image velocimetry

By observing the movement of small fluorescent particles in an electrospinning jet, we have directly measured the fluid velocity along the jet axis. The correlation between these direct velocity measurements and the velocity calculated from the jet radius using volume conservation indicates when evaporation is a significant factor. Measurements of the fluid properties of the solution used in the experiment allow us to construct a plot of Deborah number as a function of position along the jet. Our data also indicate transverse movement at the beginning of the fluid jet, potentially indicating the precursor to the macroscopic bending instability.