Significance of Nanomaterials in Wearables: A Review on Wearable Actuators and Sensors

Together with the evolution of digital health care, the wearable electronics field has evolved rapidly during the past few years and is expected to be expanded even further within the first few years of the next decade. As the next stage of wearables is predicted to move toward integrated wearables, nanomaterials and nanocomposites are in the spotlight of the search for novel concepts for integration. In addition, the conversion of current devices and attachment‐based wearables into integrated technology may involve a significant size reduction while retaining their functional capabilities. Nanomaterial‐based wearable sensors have already marked their presence with a significant distinction while nanomaterial‐based wearable actuators are still at their embryonic stage. This review looks into the contribution of nanomaterials and nanocomposites to wearable technology with a focus on wearable sensors and actuators.     

Nanocomposites for electronic applications that can be embedded for textiles and wearables

In the present review, we have selected advances in electrospinning nanofibers that we envision to be embedded in textiles and wearables. These nanofibers have been proven to be excellent options for applications such as power generation, sensing, and communication. Their similitude with already known woven meshes makes these fibers perfect for electronically active textiles.These fibers offer well known characteristics such as mechanical flexibility, high surface area-to-volume ratio, light weight and can be tuned by carefully selecting the active materials in the precursor solution. Here we will discuss polymers with electroactive, piezoelectric, triboelectric and their composites that have been used in fiber structures by using the electrospinning technique.     

A comparison of wet-extracted coconut oils prepared under hot and cold conditions

Virgin coconut oil was prepared by four wet extraction methods which included hot extraction by boiling coconut milk, and three cold extraction methods by centrifugation, fermentation, and chilling followed by thawing of coconut milk. The chemical characteristics related to both saponifiable and unsaponifiable fractions of oils were evaluated. Quality parameters such as peroxide value, iodine value, saponification value, acid value, and moisture content of the four oils remain within the acceptable range for edible purposes. Hot conditions incorporate a richer phenolic profile, a higher α-tocopherol content, and a higher β-carotene content in coconut oil. Epimerization and hydrolysis of the phenolic compounds occur depending on the extraction conditions. The longest shelf-life of the coconut oil prepared under hot conditions may be due to the relatively lower contents of moisture, free acids, peroxides, and higher contents of phenolic compounds, α-tocopherol, and β-carotene in hot-extracted coconut oil. Contrary to popular belief, hot and wet extraction conditions may produce higher quality coconut oil compared to cold extraction conditions.     

Spontaneous Covalent Self‐Assembly of the Azoarcus Ribozyme from Five Fragments

Spontaneous covalent assembly of short RNA fragments has been proposed as a plausible prebiotically relevant pathway to a self‐reproducing system. We previously showed that the Azoarcus group I intron could self‐assemble from four RNA fragments. Here, we extended this fragmentation to five RNAs that averaged <40 nucleotides in length. We optimized this reaction and showed that a dehydration–rehydration sequence was the most effective means to date to shift the self‐assembly equilibrium from reactants to products.     

Antimicrobial and Anti-Biofilm Peptide Octominin for Controlling Multidrug-Resistant Acinetobacter baumannii

Acinetobacter baumannii is a serious nosocomial pathogen with multiple drug resistance (MDR), the control of which has become challenging due to the currently used antibiotics. Our main objective in this study is to determine the antibacterial and antibiofilm activities of the antimicrobial peptide, Octominin, against MDR A. baumannii and derive its possible modes of actions. Octominin showed significant bactericidal effects at a low minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of 5 and 10 µg/mL, respectively. Time-kill kinetic analysis and bacterial viability tests revealed that Octominin showed a concentration-dependent antibacterial activity. Field-emission scanning electron microscopy (FE-SEM) analysis revealed that Octominin treatment altered the morphology and membrane structure of A. baumannii. Propidium iodide (PI) and reactive oxygen species (ROS) generation assays showed that Octominin increased the membrane permeability and ROS generation in A. baumannii, thereby causing bacterial cell death. Further, a lipopolysaccharides (LPS) binding assay showed an Octominin concentration-dependent LPS neutralization ability. Biofilm formation inhibition and eradication assays further revealed that Octominin inhibited biofilm formation and showed a high biofilm eradication activity against A. baumannii. Furthermore, up to a concentration of 100 µg/mL, Octominin caused no hemolysis and cell viability changes in mammalian cells. An in vivo study in zebrafish showed that the Octominin-treated group had a significantly higher relative percentage survival (54.1%) than the untreated group (16.6%). Additionally, a reduced bacterial load and fewer alterations in histological analysis confirmed the successful control of A. baumannii by Octominin in vivo. Collectively, these data suggest that Octominin exhibits significant antibacterial and antibiofilm activities against the multidrug-resistant A. baumannii, and this AMP can be developed further as a potent AMP for the control of antibiotic resistance.     

Indium tin oxide coated conducting glass electrode for electrochemical destruction of textile colorants

Galvanostatic oxidation of 5.0 × 10⁻² mM textile dyes such as Eosin Y (EY) and Orange II (Or II) was carried out on an indium tin oxide (ITO) coated glass anode in the presence of 1.0 × 10⁻² mM KCl solution at pH 4.0 and 6.0. The degradation results of EY were compared with that of highly stable azo dyes (Or II). EY dye solution with a concentration of 5.0 × 10⁻² mM is totally decolorized in 30 min at an electrical charge (Q) 0.067 A h dm⁻³ while 5.0 × 10⁻² mM Or II degraded in a little less than an hour at the same electrical charge density. The decay kinetics of dyes follows a pseudo first-order reaction. The degradation of dyes is faster in acidic pH values than in basic pH values. Electrochemical degradation results show significant decrease in chemical oxygen demand (COD) values after electrodegradation of textile dyes. The key advantage of the ITO conducting glass anode is that the deposition of polymeric materials on the anode surface during electro-degradation of textile dyes is absent and therefore the electrode fouling is not observed. Hence, the ITO anodes can be employed an extended period without loss of activity.     

Facile synthesis of electrospun C@NiO/Ni nanofibers as an electrocatalyst for hydrogen evolution reaction

Hydrogen evolution reaction (HER) is considered to be one of the most important electrochemical reactions from both fundamental and application perspective to produce hydrogen. Polyacrylonitrile (PAN) based carbon (C)@NiO/Ni nanofibers were fabricated via simple electrospinning method. The as-prepared C@NiO/Ni nanofibers were characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy Energy Dispersive X-ray Spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectra. The SEM and TEM analyses revealed that NiO/Ni nanoparticles distributed on the PAN based carbon nanofibers. EDS, XPS and XRD results confirm the presence of the nanoparticles. The catalytic activity and durability of C@NiO/Ni nanofibers containing different weight ratio of Ni salt content (2%, 3%, & 4%) were examined for HER in 1 M KOH solution. It has been observed that C@NiO/Ni nanofibers containing Ni content (4%) showed the highest catalytic activity. It indicates that the catalytic activity of electrocatalyst can be enhanced by increasing the effective active sites. Noteworthy to mention here that the nanofibers catalyst reached a current density of 60 mA/cm². The as-prepared catalyst showed remarkable stability up to 22 h and retained 99% of its initial activity even after 16 h of reaction.     

Engineering of the Heterointerface of Porous Carbon Nanofiber–Supported Nickel and Manganese Oxide Nanoparticle for Highly Efficient Bifunctional Oxygen Catalysis

Constructing heterointerfaces between metals and metal compounds is an attractive strategy for the fabrication of high performance electrocatalysts. However, realizing the high degree of fusion of two different metal components to form heterointerfaces remains a great challenge, since the different metal components tend to grow separately in most cases. Herein, by employing carboxyl‐modified carbon nanotubes to stabilize different metal ions, the engineering of abundant Ni|MnO heterointerfaces is achieved in porous carbon nanofibers (Ni|MnO/CNF) during the electrospinning–calcination process. Remarkably, the resulting Ni|MnO/CNF catalyst exhibits activities that are among the best reported for the catalysis of both the oxygen reduction and oxygen evolution reactions. Moreover, the catalyst also demonstrates high power density and long cycle life in Zn–air batteries. Its superior electrochemical properties are mainly ascribed to the synergy between the engineering of oxygen‐deficient Ni|MnO heterointerfaces with a strong Ni/Mn alloying interaction and the 1D porous CNF support. This facile anchoring strategy for the initiation of bimetallic heterointerfaces creates appealing opportunities for the potential use of heteronanomaterials in practical sustainable energy applications.     

Ionic conductivity of PEO9: Cu(CF3SO3)2: Al2O3 nano-composite solid polymer electrolyte

Cu⁺⁺ ion containing solid polymer electrolytes exhibit interesting electrochemical properties. In particular, the polymer electrolyte PEO₉:Cu(CF₃SO₃)₂ made by complexing copper triflate (CuTf₂) with PEO appears to show scientifically intriguing transport properties. Although some copper ion transport in these systems has been seen from plating stripping processes, the detailed mechanism of ionic transport and the species involved are yet to be established. In order to obtain enhanced ionic conductivities and also to contribute towards understanding the ionic transport process in Cu⁺⁺ ion containing, PEO based composite polymer electrolytes, we have studied the system PEO₉: CuTf₂: Al₂O₃ incorporating 10 wt.% of alumina filler particles of grain size 10 μm, 37 nm, 10–20 nm and also particles of pore size 5.8 nm. Thermal and electrical measurements show that the system remains amorphous down to room temperature. The composite electrolyte is predominantly an ionic conductor with electronic conductivity less than 2%. The triflate (CF₃SO₃⁻) anions appear to be the dominant carriers. The presence of alumina grains has enhanced the conductivity significantly from room temperature up to 100 °C. The nano-porous grains with 5.8 nm pore size and 150 m²/g specific surface area exhibited the maximum conductivity enhancement. This enhancement has been attributed to Lewis acid–base type surface interactions of ionic species with O²⁻ and OH⁻ groups on the filler grain surface.