Facile Access to Wearable Device via Microfluidic Spinning of Robust and Aligned Fluorescent Microfibers

Robust Gradient Hydrogel-Loaded Nanofiber Fleshy Artificial Skin Via A Coupled Microfluidic Electrospinning-Reactive Coating Strategy

Skin regeneration attracts tremendous interest due to the important role of skin for human protection and beauty. Thus, methods allowing artificial skin to be carried out in a controllable fashion are potentially important for wound healing, which involves an intersection of materials, medicine, biology, and other disciplines. Herein, aiming at a new general methodology for fleshy materials, a new hydrogel-loaded hydrophobic-hydrophilic nanofiber fleshy artificial skin is designed and fabricated. The gradient hydrogel-loaded nanofiber artificial skin integrates both advantages of nanofiber and hydrogel, exhibiting fleshy feature (comparability to real skin in terms of appearance, texture, and function), excellent air permeability, compatibility, and good mechanical and antibacterial property. Interestingly, the efficient transport channels are formed throughout the hydrogel-loaded nanofiber structure, which is beneficial for water absorption and transfer. These advantages enable the establishment of a moist and favorable microenvironment; thus, greatly accelerating wound healing process. This work couples microfluidic electrospinning with reactive coating technique, which is in favor of material design and fabrication with controllable and uniform structures. The hydrogel-loaded nanofiber fleshy artificial skin shows comparability to real skin in terms of beauty, texture, and function, which would definitely provide new opportunities for the further optimization and upgrading of artificial skin.

Robust microfluidic construction of polyvinyl pyrrolidone microfibers incorporated with W/O emulsions stabilized by amphiphilic konjac glucomannan

In this work, we prepared polyvinyl pyrrolidone (PVP) microfibers incorporated water-in-oil (W/O) emulsions. The W/O emulsions were fabricated by hexadecyl konjac glucomannan (HKGM, emulsifier), corn oil (oil phase) and purple corn anthocyanins (PCAs, water phase). The structures and functions of emulsions and microfibers were characterized by confocal laser scanning (CLSM) and scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), Raman and nuclear magnetic resonance (NMR) spectroscopy. The results showed that W/O emulsions exhibited good storage stability for 30 d. Microfibers presented ordered and uniform arrays. Compared with pure PVP microfiber films, the addition of W/O emulsions with PCAs improved the water resistance (WVP from 1.28 to 0.76 g mm/m² day kPa), mechanical strength (Elongation at break from 18.35 % to 49.83 %), antioxidation (free radical scavenging rate from 2.58 % to 16.37 %), and antibacterial activity (inhibition zone against E. coli: 27.33 mm and inhibition zone against S. aureus: 28.33 mm) of microfiber films. Results showed that microfiber film exhibited controlled release of PCAs in W/O emulsions, and about 32 % of the PCAs were released from the microfiber film after 340 min. The as-prepared microfiber films exhibited potential applications for food packaging.

Microfluidic preparation of optical sensors for biomedical applications

Optical biosensors are platforms that translate biological information into detectable optical signals, and have extensive applications in various fields due to their characteristics of high sensitivity, high specificity, dynamic sensing, etc. The development of optical sensing materials is an important part of optical sensors. In this review, we emphasize the role of microfluidic technology in the preparation of optical sensing materials and the application of the derived optical sensors in the biomedical field. We first present some common optical sensing mechanisms and the functional responsive materials involved. Then, we describe the preparation of these sensing materials by microfluidics. Afterward, we enumerate the biomedical applications of these optical materials as biosensors in disease diagnosis, drug evaluation, and organ-on-a-chip. Finally, we discuss the challenges and prospects in this field.

Microfluidic-assisted fiber production: Potentials, limitations, and prospects

Besides the conventional fiber production methods, microfluidics has emerged as a promising approach for the engineered spinning of fibrous materials and offers excellent potential for fiber manufacturing in a controlled and straightforward manner. This method facilitates low-speed prototype synthesis of fibers for diverse applications while providing superior control over reaction conditions, efficient use of precursor solutions, reagent mixing, and process parameters. This article reviews recent advances in microfluidic technology for the fabrication of fibrous materials with different morphologies and a variety of properties aimed at various applications. First, the basic principles, as well as the latest developments and achievements of microfluidic-based techniques for fiber production, are introduced. Specifically, microfluidic platforms made of glass, polymers, and/or metals, including but not limited to microfluidic chips, capillary-based devices, and three-dimensional printed devices are summarized. Then, fiber production from various materials, such as alginate, gelatin, silk, collagen, and chitosan, using different microfluidic platforms with a broad range of cross-linking agents and mechanisms is described. Therefore, microfluidic spun fibers with diverse diameters ranging from submicrometer scales to hundreds of micrometers and structures, such as cylindrical, hollow, grooved, flat, core-shell, heterogeneous, helical, and peapod-like morphologies, with tunable sizes and mechanical properties are discussed in detail. Subsequently, the practical applications of microfluidic spun fibers are highlighted in sensors for biomedical or optical purposes, scaffolds for culture or encapsulation of cells in tissue engineering, and drug delivery. Finally, different limitations and challenges of the current microfluidic technologies, as well as the future perspectives and concluding remarks, are presented.

Bioinspired Fibers with Controlled Wettability: From Spinning to Application

Our knowledge on spider silks shows the importance of joining heterogeneous structures and surface chemical compositions in preparing fibers, fibrous surfaces, and 3D materials with a controllable wettability. We start our review with spider silk and proceed to the historical development of nature-inspired spinning processes, their products, and their advantages and disadvantages. Relevant wetting states are then summarized in fiber-based systems. Recent applications are reviewed, including one-dimensional spindle-knotted fibers for highly efficient fog harvesting, long-distance transport, and stimulus-responsive wettability and two-dimensional spindle-knotted fibrous systems for water collection, functional surfaces, and filtration. Finally, we offer some perspective on future research trends regarding biomimetic fibers for wetting-controlled engineering.

Review of microfluidic approaches for fabricating intelligent fiber devices: importance of shape characteristics

Shape characteristics, which include the physical dimensions (scale), apparent morphology, surface features, and structure, are essential factors of fibrous materials and determine many of their properties. Microfluidic technologies have recently been proposed as an approach for producing one-dimensional (1D) fibers with controllable shape characteristics and particle alignment, which impart specific functionality to the fiber. Moreover, superfine 1D fibers with a high surface area and ordered structure have many potential applications as they can be directly braided or woven into textiles, clothes, and tissues with two- or three-dimensional (2D or 3D) structures. Previous reviews of microfluidic spinning have not focus on the importance of the shape characteristic on fiber performance and their use in intelligent fiber design. Here, the latest achievements in microfluidic approaches for fiber-device fabrication are reviewed considering the underlying preparation principles, shape characteristics, and functionalization of the fibers. Additionally, intelligent fiber devices with shapes tailored by microfluidic approaches are discussed, including 1D sensors and actuators, luminous fibers, and devices for encoding, energy harvesting, water collection, and tissue engineering applications. Finally, recent progress, challenges, and future perspectives of the microfluidic approaches for fiber device fabrication are discussed.

Microfluidic spinning-induced heterotypic bead-on-string fibers for dual-cargo release and wound healing

The preparation of dual-release pharmaceutical microfibers provides an ideal material for new biomedical applications. We describe a microfluidic spinning method for engineering heterotypic bead-on-string fibers with the ability to carry dual cargos and to deliver on demand. The core of our technology is to combine microfluidic spinning with biomaterial preparation, in which hydrophobic and hydrophilic cargos can be integrated into a bead-on-string microfiber structure. We demonstrate the loading of bovine serum albumin (BSA) in the sodium alginate phase and ibuprofen in the polylactic acid (PLA) phase, respectively. The heterotypic bead-on-string fibers are biocompatible and show hemostatic ability in vivo. These heterotypic bead-on-string fibers are then woven as a skin scaffold and shown to promote wound healing by loading antibacterial and anti-inflammatory cargos.

Macroscopic Self-Assembly of Gel-Based Microfibers toward Functional Nonwoven Fabrics

Macroscopic self-assembly has increasingly attracted numerous concerns because of the facile fabrication of complex structures and diversified morphologies. Key challenges still remain to design high-performance building blocks to increase the efficiency and diversity of macroscopic self-assembly. Here, we designed triple noncovalent interactions (carboxyl-Zn²⁺ coordination, host-guest interactions, and hydrogen bonding interactions) to enhance the interactions between self-healing fibers, constructing multidimensional nonwoven fiber-based fabrics through macroscopic self-assembly without further postprocessing. Profiled from the strong interactions generated from triple noncovalent interactions, ordered two-dimensional plane and three-dimensional spiral gel fabrics were fabricated using polyvinyl pyrrolidone/gel-based fibers as building blocks toward a human motion sensor. Moreover, we demonstrated that the macroscopic self-assembly strategy is universal to construct three-dimensional film-based fabrics toward wound dressing based on the triple noncovalent interactions between two-dimensional films. This macroscopic self-assembly approach provides an alternative strategy to fabricate gel fabrics for various applications.

Nano-Micro Dimensional Structures of Fiber-Shaped Luminous Halide Perovskite Composites for Photonic and Optoelectronic Applications

Perovskite nanomaterials have been revealed as highly luminescent structures regarding their dimensional confinement. In particular, their promising potential lies behind remarkable luminescent properties, including color tunability, high photoluminescence quantum yield, and the narrow emission band of halide perovskite (HP) nanostructures for optoelectronic and photonic applications such as lightning and displaying operations. However, HP nanomaterials possess such drawbacks, including oxygen, moisture, temperature, or UV lights, which limit their practical applications. Recently, HP-containing polymer composite fibers have gained much attention owing to the spatial distribution and alignment of HPs with high mechanical strength and ambient stability in addition to their remarkable optical properties comparable to that of nanocrystals. In this review, the fabrication methods for preparing nano-microdimensional HP composite fiber structures are described. Various advantages of the luminescent composite nanofibers are also described, followed by their applications for photonic and optoelectronic devices including sensors, polarizers, waveguides, lasers, light-down converters, light-emitting diode operations, etc. Finally, future directions and remaining challenges of HP-based nanofibers are presented.

Fluctuation of photon-releasing with ligand coordination in polyacrylonitrile-based electrospun nanofibers

Multivariate terbium-complexes were incorporated into polyacrylonitrile (PAN) and electrospun into flexible multifunctional nanofibers with a uniform diameter of ~200 nm. Fluorescence comparison in multi-ligand-binding nanofibers under ultraviolet (UV) radiation verifies that the differentiated β-diketone ligands with dual functions are the primary cause of the spectral fluctuation, adequately illustrating the available methods for the quantification of intermolecular reciprocities between organic ligands and central Tb3+ ions. Especially under 308 nm UVB-LED pumping, the total emission spectral power of supramolecular Tb-complexes/PAN nanofibers are identified to be 2.88 µW and the total emission photon number reaches to 7.94 × 1012 cps which are nearly six times higher than those of the binary complex ones in the visible region, respectively. By modifying the sorts of organic ligands, the luminous flux and luminous efficacy of multi-ligand Tb-complexes/PAN nanofibers are up to 1553.42 μlm and 13.72 mlm/W, respectively. Efficient photon-releasing and intense green-emission demonstrate that the polymer-capped multi-component terbium-complexes fibers have potential prospects for making designable flexible optoelectronic devices.

Multifunctional Micro/Nanoscale Fibers Based on Microfluidic Spinning Technology

Superfine multifunctional micro/nanoscale fibrous materials with high surface area and ordered structure have attracted intensive attention for widespread applications in recent years. Microfluidic spinning technology (MST) has emerged as a powerful and versatile platform because of its various advantages such as high surface-area-to-volume ratio, effective heat transfer, and enhanced reaction rate. The resultant well-defined micro/nanoscale fibers exhibit controllable compositions, advanced structures, and new physical/chemical properties. The latest developments and achievements in microfluidic spun fiber materials are summarized in terms of the underlying preparation principles, geometric configurations, and functionalization. Variously architected structures and shapes by MST, including cylindrical, grooved, flat, anisotropic, hollow, core-shell, Janus, heterogeneous, helical, and knotted fibers, are emphasized. In particular, fiber-spinning chemistry in MST for achieving functionalization of fiber materials by in situ chemical reactions inside fibers is introduced. Additionally, the applications of the fabricated functional fibers are highlighted in sensors, microactuators, photoelectric devices, flexible electronics, tissue engineering, drug delivery, and water collection. Finally, recent progress, challenges, and future perspectives are discussed.

Fiber-Spinning-Chemistry Method toward In Situ Generation of Highly Stable Halide Perovskite Nanocrystals

All-inorganic halide perovskite nanocrystals (PNCs) have drawn increasing attention owing to their splendid optical properties. However, such nanomaterials suffer from intrinsic instability, greatly limiting their practical application. Meanwhile, environmental regulation has restricted the emissions of volatile organic compounds (VOCs), initiating a search for alternative approaches to PNC synthesis and film forming. Herein, fiber-spinning chemistry (FSC) is proposed for easy-to-perform synthesis of highly stable PNC fibrous films. The FSC process utilizes spinning fibers as reactors, reducing the generation of VOCs. This method enables the fabrication of CsPbX3 (X = Cl, Br, I) PNCs/poly(methyl methacrylate)/thermoplastic polyurethanes fibrous films at room temperature in one step, exhibiting tunable emission between 450 and 660 nm. Significantly, the in situ generation of PNCs in hydrophobic core-shell nanofibers results in highly improved fluorescence stability. PNCs/polymer fibrous films keep constant in photoluminescence (PL) after storage at atmosphere for 90 d and retain 82% PL after water immersion for 120 h (vs fluorescence quenching in 10 d in air or 5 h in water for pristine PNCs). The PNCs/polymer fibrous films endowed with superior optical stability and great flexibility show promising potentials in flexible optoelectronic applications. This work paves a facile way toward high-performance nanoparticles/polymer fibrous films.

Microfluidic spinning of poly (methyl methacrylate)/konjac glucomannan active food packaging films based on hydrophilic/hydrophobic strategy

Here, inspired by the hydrophilic/hydrophobic theory, a novel konjac glucomannan/poly (methyl methacrylate)/chlorogenic acid (KGM/PMMA/CGA) food packaging film was successfully fabricated via microfluidic spinning technology (MST). The results of fourier transform infrared spectroscopy and x-ray diffraction confirmed the formation of hydrogen bonds in the films, which lead to the enhanced mechanical properties. Thermogravimetric analysis and differential scanning calorimetry showed excellent thermal stability of the films. Water vapor permeability (1.47 × 10^-5 ± 0.11 g/(m⋅h⋅kPa)) and water contact angle (89.2°) measurement proved that the films were hydrophobic. The good swelling degree (85.18 ± 15.65%) indicated film's potentials in releasing CGA. More importantly, KGM played a key role in the antibacterial activities against Staphylococcus aureus (8.5 ± 3.5 mm) and Escherichia coli (6.5 ± 2.1 mm) by utilizing its hydrophilicity. Thus, our present work may provide a new idea for constructing active food packaging films with significant performances based on hydrophilic/hydrophobic strategy.

High pairing rate Janus-structured microfibers and array: high-efficiency conjugate electrospinning fabrication, structure analysis and co-instantaneous multifunctionality of anisotropic conduction, magnetism and enhanced red fluorescence

A highly efficient and convenient conjugate electrospinning technique is employed to obtain high pairing rate Janus-structured microfibers in electrospun products by optimizing the spinning conditions. In addition, a Janus-structured microfiber array rendering tri-functional performance of tunable magnetism, electrically anisotropic conduction and increased fluorescence is prepared via the same technique using a rotating device as a fiber collector. The array is composed of an ordered arrangement of Janus-structured microfibers. The extraordinary Janus structure and oriented arrangement endow the Janus-structured microfibers with excellent fluorescence. The fluorescence intensity of the Janus-structured microfiber array is, respectively, 1.21, 14.3 and 20.3 times higher than that of the Janus-structured microfiber non-array, the composite microfiber array and the composite microfiber non-array. The Janus-structured microfiber array has a similar saturation magnetization to the contradistinctive specimens. Additionally, the magnetism of the Janus-structured microfiber array can be modulated with different mass ratios of Fe₃O₄ nanoparticles (NPs), and the conductance ratio between the length direction and diameter direction of the Janus-structured microfibers for the array can be tuned from 10³ to 10⁶ by adding a higher percentage of polyaniline (PANI). Our new findings have established a highly efficient conjugate electrospinning technique to prepare Janus-structured microfibers of high pairing rate, and complete isolation of fluorescent material from magnetic nanoparticles and conductive material is accomplished in the Janus-structured microfibers to ensure high fluorescence intensity without a notably disadvantageous influence of dark-colored substances. More importantly, the fabrication technique for the Janus-structured microfibers can be generalized to manufacture other Janus-structured multifunctional materials.

High pairing rate Janus-structured microfibers and their arrays, rendering simultaneous anisotropic conduction, magnetism and fluorescence, are successfully fabricated via conjugate electrospinning.