Search Results (17)

Flexible supercapacitors have emerged as pivotal energy storage components in wearable smart electronic systems, owing to their exceptional electrochemical performance. However, the widespread application of flexible supercapacitors in smart electronic devices is significantly hindered by the developmental bottleneck of high-performance anode materials. In this study, a novel electrode composed of surface-modified Fe₂O₃ nanoneedles uniformly coated with a polypyrrole (PPy) film and anchored on Co-MOF-derived N-C nanoflake arrays (PPy/Fe₂O₃/N-C) is designed. This composite electrode, grown in situ on carbon cloth (CC), demonstrated outstanding specific capacity, rate performance, and mechanical flexibility, attributed to its unique hierarchical 3D arrayed structure and the protective PPy layer. The fabricated PPy/Fe₂O₃/N-C@CC (P-FONC) composite electrode exhibited an excellent specific capacitance of 356.6 mF cm⁻² (143 F g⁻¹) at a current density of 2 mA cm⁻². The current density increased to 20 mA cm⁻², and the composite electrode material preserved a specific capacitance of 278 mF cm⁻² (112 F g⁻¹). Furthermore, the assembled quasi-solid-state Mn/Fe asymmetric supercapacitor, configured with P-FONC as the negative electrode and MnO₂/N-C@CC as the positive electrode, demonstrated robust chemical stability and notable mechanical flexibility. This study sheds fresh light on the creation of three-dimensional composite electrode materials for highly efficient, flexible energy storage systems. Full article

Intracellular delivery, the process of transporting substances into cells, is crucial for various applications, such as drug delivery, gene therapy, cell imaging, and regenerative medicine. Among the different approaches of intracellular delivery, mechanoporation stands out by utilizing mechanical forces to create temporary pores on cell membranes, enabling the entry of substances into cells. This method is promising due to its minimal contamination and is especially vital for stem cells intended for clinical therapy. In this review, we explore various mechanoporation technologies, including microinjection, micro–nano needle arrays, cell squeezing through physical confinement, and cell squeezing using hydrodynamic forces. Additionally, we highlight recent research efforts utilizing mechanoporation for stem cell studies. Furthermore, we discuss the integration of mechanoporation techniques into microfluidic platforms for high-throughput intracellular delivery with enhanced transfection efficiency. This advancement holds potential in addressing the challenge of low transfection efficiency, benefiting both basic research and clinical applications of stem cells. Ultimately, the combination of microfluidics and mechanoporation presents new opportunities for creating comprehensive systems for stem cell processing. Full article

Real-time monitoring of physiological indicators inside the body is pivotal for contemporary diagnostics and treatments. Implantable electrodes can not only track specific biomarkers but also facilitate therapeutic interventions. By modifying biometric components, implantable electrodes enable in situ metabolite detection in living tissues, notably beneficial in invasive glucose monitoring, which effectively alleviates the self-blood-glucose-managing burden for patients. However, the development of implantable electrochemical electrodes, especially multi-channel sensing devices, still faces challenges: (1) The complexity of direct preparation hinders functionalized or multi-parameter sensing on a small scale. (2) The fine structure of individual electrodes results in low spatial resolution for sensor functionalization. (3) There is limited conductivity due to simple device structures and weakly conductive electrode materials (such as silicon or polymers). To address these challenges, we developed multiple-channel electrochemical microneedle electrode arrays (MCEMEAs) via a separated functionalization and assembly process. Two-dimensional microneedle (2dMN)-based and one-dimensional microneedle (1dMN)-based electrodes were prepared by laser patterning, which were then modified as sensing electrodes by electrochemical deposition and glucose oxidase decoration to achieve separated functionalization and reduce mutual interference. The electrodes were then assembled into 2dMN- and 1dMN-based multi-channel electrochemical arrays (MCEAs), respectively, to avoid damaging functionalized coatings. In vitro and in vivo results demonstrated that the as-prepared MCEAs exhibit excellent transdermal capability, detection sensitivity, selectivity, and reproducibility, which was capable of real-time, in situ glucose concentration monitoring. Full article

Low-cost and high-performance electrocatalysts are crucial for water-splitting reactions. Some non-precious metal electrocatalysts are proved to be good replacements for noble metal due to the unique electronic structure features and excellent performance. In this work, binary Ni-Co-based layered double hydroxide nanoneedle arrays electrocatalysts are synthesized on Ni foam (NF) via a hydrothermal process. The microstructure and the catalytic performance of the catalyst changes significantly by regulating the molar ratio of Ni/Co. The theoretical analysis confirmed that the as-prepared NiCo-LDH nanoneedle arrays reveal a potential behavior in oxygen evolution reaction (OER) at a lower overpotential of 305 mV at 10.0 mA cm⁻² and a Tafel slope of 110.38 mV dec⁻¹. The double-layer capacitance (C_dl) is 776 mF cm⁻², which indicates that there are many active sites that are exposed on the surface for the electrocatalytic reaction. The results provide an obvious reference value to other types of LDH catalysts for the development of water electrolysis. Full article

Solving high electrical-energy input for pollutants degradation is one of the core requirements for the practical application of photoelectrocatalytic (PEC) technology. Herein, we developed a self-driven dual-photoelectrode PEC system (TiO₂ NNs-Co₃O₄) composed of a TiO₂ nanoneedle arrays (TiO₂ NNs) photoanode and Co₃O₄ photocathode for the first time. Under light-emitting-diode (LED) illumination, the bias-free TiO₂ NNs-Co₃O₄ PEC system exhibited excellent PEC performance, with an internal bias as high as 0.19 V, achieving near complete degradation (99.62%) of sulfamethazine (SMT) with a pseudo-first-order rate constant of 0.042 min⁻¹. The influences of solution pH, typical inorganic anions, natural organic matter, and initial SMT concentration on the PEC performance were investigated. Moreover, the main reactive oxygen species (h⁺, ^•OH, ^•O₂⁻) in the dual-photoelectrode PEC system for SMT decomposition were elaborated. The practical application feasibility for efficient water purification of this unbiased PEC system was evaluated. It was proved that the TiO₂ NNs photoanode provided a negative bias while the Co₃O₄ photocathode provided a positive bias for the photoanode, which made this system operate without external bias. This work elucidated the cooperative mechanism of photoelectrodes, providing guidance to develop a sustainable, efficient, and energy-saving PEC system for wastewater treatment. Full article

Current procedures for transdermal drug delivery (TDD) have associated limitations including poor administration of nucleic acid, small or large drug molecules, pain and stress for needle phobic people. A painless micro-sized device capable of delivering drugs easily and efficiently, eliminating the disadvantages of traditional systems, has yet to be developed. While polymeric-based microneedle (MN) arrays have been used successfully and clinically as TDD systems, these devices lack mechanical integrity, piercing capacity and the ability to achieve tailored drug release into the systemic circulation. Recent advances in micro/nano fabrication techniques using Additive Manufacturing (AM), also known as 3D printing, have enabled the fabrication of metallic MN arrays, which offer the potential to overcome the limitations of existing systems. This review summarizes the different types of MNs used in TDD and their mode of drug delivery. The application of MNs in the treatment of a range of diseases including diabetes and cancer is discussed. The potential role of solid metallic MNs in TDD, the various techniques used for their fabrication, and the influence of their geometrical characteristics (e.g., shape, size, base diameter, thickness, and tip sharpness) on effective TDD are explored. Finally, the potential and the future directions relating to the optimization of metallic MN arrays for TDD are highlighted. Full article

This study used a rapid and simple microwave-assisted synthesis method to grow ZnO nanoneedle arrays on the silicon substrate with the ZnO seed layer. The effects of reaction temperature and time on the lengths of ZnO nanoneedle arrays were investigated. The appropriate temperature programming step can grow the longer ZnO nanoneedle arrays at the same reaction time (25 min), which is 2.08 times higher than without the temperature programming step. The geometry of the ZnO nanoneedle arrays features a gradual decrease from the Si substrate to the surface, which provides an excellent progressive refractive index between Si and air, resulting in excellent antireflection properties over an extensive wavelength range. In addition, the ZnO nanoneedle arrays exhibit a suitable structure for uniform deposition of Ag nanoparticles, which can provide three-dimensional hot spots and surface active sites, resulting in higher surface-enhanced Raman scattering (SERS) enhancement, high uniformity, high reusability, and low detection limit for R6G molecule. The ZnO/Ag nanoneedle arrays can also reveal a superior SERS-active substrate detecting amoxicillin (10⁻⁸ M). These results are promising for applying the SERS technique for rapid low-concentration determination in different fields. Full article

Polymer surfaces are increasingly being functionalized with micro- and nano- surface features using mass replication methods such as injection moulding. An example of these are microneedle arrays, which contain needle-like microscopic structures, which facilitate drug or vaccine delivery in a minimally invasive way. In this study, the replication fidelity of two types of solid polycarbonate microneedles was investigated using injection compression moulding and conventional injection moulding. Using a full factorial design of experiments for the injection moulding process, it was found that the volumetric injection rate had the largest positive effect on the replication fidelity. The mould temperature and holding pressure were also found to have a positive effect, while the effect of the melt temperature was found to be insignificant for the considered temperature range. For the injection compression moulding process, it was found that a larger compression stroke resulted in a better replication fidelity. A comparison between the replication fidelity for the injection moulding and injection compression moulding indicated that the injection compression moulding process resulted in a higher and more uniform replication fidelity. Using finite element flow simulations, a higher and more evenly distributed cavity pressure was observed compared to the conventional injection moulding process. Full article

It is of great significance to design electrochemical energy conversion and storage materials with excellent performance to fulfill the growing energy demand. Bimetallic cobalt/nickel-based electrode materials exhibit excellent electrical conductivity compared to mono oxides. However, their potential as electrode materials for high-performance supercapacitors (SCs) is limited because of their poor cycling stability and high-capacity fading. This work demonstrates the synthesis of binder-free bimetallic NiCo₂O₄ nano-needles supported on CC (NCO@CC) via a facile and scalable hydrothermal process. Excellent electrical conductivity and interconnected nanostructure of NCO@CC nano-needles provide the fast transfer of electrons with numerous channels for ion diffusion. Owing to such features, the binder-free NCO@CC electrode for SC discloses excellent specific capacitance (1476 Fg⁻¹ at 1.5 Ag⁻¹) with 94.25% capacitance retention even after 5000 cycles. From these outstanding electrochemical performances, it can be inferred that NCO@CC nano-needle array-structured electrodes may be potential candidates for SC applications. Full article

An economical and efficient method is developed for preparing flexible cathodes. In this work, a dense mesoporous Co₃O₄ layer was first hydrothermally grown in situ on the surface of chopped carbon fibers (CFs), and then carbon fiber paper (Co₃O₄/CP) was prepared by a wet papermaking process as a flexible zinc-air battery (ZAB). The high-performance air cathode utilizes the high specific surface area of a single chopped carbon fiber, which is conducive to the deposition and adhesion of the Co₃O₄ layer. Through the wet papermaking process, Co₃O₄/CP has ultra-thin, high mechanical stability and excellent electrical conductivity. In addition, the assembled ZAB exhibits relatively excellent electrochemical performance, with a continuous cycle of more than 180 times at a current density of 2 mA·cm⁻². The zinc-air battery can maintain a close fit and work stably and efficiently even under high bending conditions. This process of combining single carbon fibers to prepare ultra-thin, high-density, high-conductivity carbon fiber paper through a papermaking process has huge application potential in the field of flexible wearables. Full article

Transdermal vaccination route using biodegradable microneedles is a rapidly progressing field of research and applications. The fear of painful needles is one of the primary reasons most people avoid getting vaccinated. Therefore, developing an alternative pain-free method of vaccination using microneedles has been a significant research area. Microneedles comprise arrays of micron-sized needles that offer a pain-free method of delivering actives across the skin. Apart from being pain-free, microneedles provide various advantages over conventional vaccination routes such as intramuscular and subcutaneous. Microneedle vaccines induce a robust immune response as the needles ranging from 50 to 900 μm in length can efficiently deliver the vaccine to the epidermis and the dermis region, which contains many Langerhans and dendritic cells. The microneedle array looks like band-aid patches and offers the advantages of avoiding cold-chain storage and self-administration flexibility. The slow release of vaccine antigens is an important advantage of using microneedles. The vaccine antigens in the microneedles can be in solution or suspension form, encapsulated in nano or microparticles, and nucleic acid-based. The use of microneedles to deliver particle-based vaccines is gaining importance because of the combined advantages of particulate vaccine and pain-free immunization. The future of microneedle-based vaccines looks promising however, addressing some limitations such as dosing inadequacy, stability and sterility will lead to successful use of microneedles for vaccine delivery. This review illustrates the recent research in the field of microneedle-based vaccination. Full article

Copper nitride nanowire arrays were synthesized by an ammonolysis reaction of copper oxide precursors grown on copper surfaces in an ammonia solution. The starting Cu films were deposited on a silicon substrate using two different methods: thermal evaporation (30 nm thickness) and electroplating (2 μm thickness). The grown CuO or CuO/Cu(OH)₂ architectures were studied in regard to morphology and size, using electron microscopy methods (SEM, TEM). The final shape and composition of the structures were mostly affected by the concentration of the ammonia solution and time of the immersion. Needle-shaped 2–3 μm long nanostructures were formed from the electrodeposited copper films placed in a 0.033 M NH₃ solution for 48 h, whereas for the copper films obtained by physical vapor deposition (PVD), well-aligned nano-needles were obtained after 3 h. The phase composition of the films was studied by X-ray diffraction (XRD) and selected area electron diffraction (SAED) analysis, indicating a presence of CuO and Cu(OH)₂, as well as Cu residues. Therefore, in order to obtain a pure oxide film, the samples were thermally treated at 120–180 °C, after which the morphology of the structures remained unchanged. In the final stage of this study, Cu₃N nanostructures were obtained by an ammonolysis reaction at 310 °C and studied by SEM, TEM, XRD, and spectroscopic methods. The fabricated PVD-derived coatings were also analyzed using a spectroscopic ellipsometry method, in order to calculate dielectric function, band gap and film thickness. Full article

Recently, nanostructured copper oxides formed via anodizing have been intensively researched due to their potential catalytic applications in emerging issues. The anodic Cu₂O and CuO nanowires or nanoneedles are attractive photo- and electrocatalysts since they show wide array of desired electronic and morphological features, such as highly-developed surface area. In CO₂ electrochemical reduction reaction (CO₂RR) copper and copper-based nanostructures indicate unique adsorption properties to crucial reaction intermediates. Furthermore, anodized copper-based materials enable formation of C₂₊ hydrocarbons and alcohols with enhanced selectivity. Moreover, anodic copper oxides provide outstanding turnover frequencies in electrochemical methanol oxidation at lowered overpotentials. Therefore, they can be considered as precious metals electrodes substituents in direct methanol fuel cells. Additionally, due to the presence of Cu(III)/Cu(II) redox couple, these materials find application as electrodes for non-enzymatic glucose sensors. In photoelectrochemistry, Cu₂O-CuO heterostructures of anodic copper oxides with highly-developed surface area are attractive for water splitting. All the above-mentioned aspects of anodic copper oxides derived catalysts with state-of-the-art background have been reviewed within this paper. Full article

Highly ordered anodic hafnium oxide (AHO) nanoporous or nanotubes were synthesized by electrochemical anodization of Hf foils. The growth of self-ordered AHO was investigated by optimizing a key electrochemical anodization parameter, the solvent-based electrolyte using: Ethylene glycol, dimethyl sulfoxide, formamide and N-methylformamide organic solvents. The electrolyte solvent is here shown to highly affect the morphological properties of the AHO, namely the self-ordering, growth rate and length. As a result, AHO nanoporous and nanotubes arrays were obtained, as well as other different shapes and morphologies, such as nanoneedles, nanoflakes and nanowires-agglomerations. The intrinsic chemical-physical properties of the electrolyte solvents (solvent type, dielectric constant and viscosity) are at the base of the properties that mainly affect the AHO morphology shape, growth rate, final thickness and porosity, for the same anodization voltage and time. We found that the interplay between the dielectric and viscosity constants of the solvent electrolyte is able to tailor the anodic oxide growth from continuous-to-nanoporous-to-nanotubes. Full article

The clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system is a powerful and widely used tool for genome editing. Recently, it was reported that direct delivery of Cas9-sgRNA ribonucleoproteins (RNPs) reduced off-target effects. Therefore, non-invasive, high-throughput methods are needed for direct delivery of RNPs into cells. Here, we report a novel method for direct delivery of RNPs into cells using a nanostructure with a high-aspect-ratio and uniform nanoneedles. This nanostructure is composed of tens of thousands of nanoneedles laid across a 2D array. Through insertion of the nanoneedle array previously adsorbed with Cas9-sgRNA, it was possible to deliver RNPs directly into mammalian cells for genome editing. Full article