One-step electrospinning membranes with gradual-transition wettability gradient for directional fluid transport

Self-Propelling Water Droplets on Conical Spikes with Sawtooth Surface Structure

Directional fluid transport is critical for water, energy, and biomedical applications, including passive fog harvesting. The unique shape gradient of conical structures can induce capillary pressure and drive the self-propulsion of droplets as the droplets settle on wettable sharp cones and move toward the cone base as they grow. In this work, we achieve passive droplet transport by fabricating conical spikes with sawtooth and imbricated (reversed-sawtooth) surface structures via high-resolution 3D printing. Fog harvesting experiments on various spikes indicate that the sawtooth structure exhibits the most efficient droplet mobilization toward the spike base, while the imbricated surface structure promotes isolated droplet formation with delayed transport and the smooth spikes would keep droplets stationary unless coalescences occur. Further droplet motion analysis reveals that the flat surface with imbricated structure exerts 3.5 times more hysteresis force than the sawtooth one under dry conditions and nearly twice under wet conditions. During fog harvesting, microdroplets in fog fill the teeth gaps along the water-wet sawtooth spike, and the resulting big barrel droplet exhibits a series of stop-and-go motions when it continues growing. Our quantitative analysis reveals that the interplay between the capillary and hysteresis forces is responsible for the droplet self-propulsion. Our experiments with the conical sawtooth spike array further demonstrate that the fog water harvesting rate with 10 μm teeth spacing is twice that with 20 μm spacing and triple that with 40 μm spacing.

3D-printed kirigami-inspired asymmetric dressings: custom elasticity and self-pumping for enhanced wound healing

Preventing infections and managing excessive exudate in dynamic joints are vital for effective wound treatment. Accurately fitting dressings to wound shapes remains a significant challenge, which can adversely affect both healing and patient comfort. This study introduces a self-pumping dressing with a tailored shape and tensile properties. This dressing channels excessive wound fluid in a unidirectional manner achieved by electrospinning hydrophobic nanofibers embedded with silver nanoparticles (AgNPs) onto a hydrophilic 3D-printed patch featuring a kirigami structure. By systematically adjusting the parameter-cutting length l, horizontal spacing d, and vertical spacing h, we enabled the elongation of the 3D-printed patch to range from 26% to 244%. Our personalized self-pumping dressings demonstrated effective antibacterial activity, unidirectional fluid transmission, and biocompatibility, thereby accelerating wound healing. This research establishes a promising pathway for personalized and precise local wound care.

Janus Textile: Advancing Wearable Technology for Autonomous Sweat Management and Beyond

To alleviate the discomfort caused by excessive sweating, there is a growing emphasis on developing wearable textiles that can evacuate sweat autonomously. These advanced fabrics, unlike their absorbent and retention-prone predecessors, harness the Janus structure-distinguished by its asymmetric wettability-to facilitate one-way transport of liquid. This unique characteristic has significant potential in addressing issues related to excessive bodily moisture and propelling the realm of smart wearables. This review offers a comprehensive overview of the advancements in Janus-structured textiles within the wearable field, delving into the mechanisms behind their unidirectional liquid transport, which rely on chemical gradient and curvature gradient strategies, alongside the methodologies for achieving asymmetric wettability. It further spotlights the multifaceted applications of Janus-based textiles in wearables, including moisture and thermal management, wound care, and sweat analysis. In addition to examining existing hurdles, the review also explores avenues for future innovation, envisioning a new era of Janus textiles tailored for personalized comfort and health monitoring capabilities.

Sandwiched Copper Foam with Symmetrical Wettability for Direction-Independent Fog Collection

The Janus membrane demonstrates its advantages in timely drainage and directional water transport properties for efficient fog water collection, which helps alleviate global water shortages. However, the direction-dependent collection and inefficient directional water transport properties limit its widespread application. Herein, a single-layered sandwich-structured copper foam that features a superhydrophilic inner layer and double-deck external hydrophobic layers is prepared by a simple method. This innovative architecture demonstrates direction-independent fog harvesting capabilities through the synergistic integration of symmetric wettability gradients and robust structural integrity. Such sandwiched copper foam shows its superiority in rapid directional water transport and timely drainage properties which can quickly regenerate the fresh outer hydrophobic surface as well as the direction-independent unidirectional water transport properties. The rapid directional water transport property combined with the timely drainage of the sandwiched copper foam benefits the continuous better performance of fog collection compared to that of conventional Janus membranes. Clearly, the development of such sandwiched copper foam with a direction-independent unidirectional water transport property enables the effective and durable collection of fog droplets in environments with dynamically changeable winds. Overall, this work provides a new idea for the fabrication of advanced materials for direction-independent fog collection.

Directional Liquid Transport in Thin Fibrous Matrices: Enhancement of Advanced Applications

Directional liquid transport fibrous matrices (DLTFMs) have the unique ability to direct liquid movement in a single direction through their thickness. Beyond their inherent liquid transport function, DLTFMs can also enhance the effectiveness of additional functionalities. This review focuses on recent advances in DLTFMs, particularly the role of DLTs in enhancing secondary functions. We begin with a brief overview of the historical development and major achievements in DLTFM research, followed by an outline of the classification, fabrication techniques, and basic functions derived from their natural liquid transport properties. The integration of DLT to enhance secondary functionalities such as responsiveness, thermal regulation, and wearable technology for innovative applications in various sectors is then discussed. The review concludes with a discussion of key challenges and prospects in the field, including the durability and reliability of DLT performance, the precise regulation of fluid transport rates, the resilience and longevity of DLTFMs in harsh environments, and the impact of DLT variations on performance enhancement. The goal of this review is to stimulate further innovative studies on DLTFMs and to promote their practical implementation in a variety of industries.

Development of chitosan/polycaprolactone-thymol Janus films with directional transport and antibacterial properties for meat preservation

Reducing contamination from percolate is critical to the preservation of foods with high water content, such as pork. This study aims to develop a novel active packaging material for meat preservation by precisely controlled dual-channel one-step electrospinning. Compared to traditional strategies of preparing Janus films, this method allows for greater flexibility and efficiency. The structure and properties of the Janus film are characterized by scanning electron microscopy (SEM), water contact angle (WCA), directional liquid transport investigation, Thymol release and permeation features, and biocompatibility evaluation. Moreover, the Janus film is applied to the packaging of pork with modified atmosphere packaging to demonstrate its practical application prospects in the food active packaging field. The results revealed that the two sides of the film showed completely different wettability, and the change rate of WCA increased with the increase of the scale of hydrophilic fibers. The permeation features of thymol loaded in the film was consistent with the results of antibacterial properties and biocompatibility assessment. Moreover, the Janus film can effectively prolong the shelf life, improve the quality and safety of the pork.

Multifunctional electrospun membranes with hydrophilic and hydrophobic gradients property for wound dressing

Achieving sustained and stable release of macromolecular antibacterial agents and unidirectional transport of liquids in targeted environment is still a challenge to be addressed in the management of wounds with large amounts of tissue exudates. In this work, a multilayer electrospun membrane (ethylcellulose-ethylcellulose/gelatin-quercetin/Eudragit L-100/polyethylene glycol, EC-EC/Gel-Q/EL/PEG) was designed with hydrophobic-hydrophilic gradients and drug sustained-release properties controlled by self-pumping effect and prepared using sequential electrospinning technology. The capillary force of different layers in the multilayer membrane could be controlled by precisely tuning the polymer concentrations of the inner and middle layers to extract water directly from hydrophobic inner ethylcellulose (EC) layer to hydrophilic middle ethylcellulose/gelatin (EC/Gel) layer. The droplets could not penetrate the hydrophobic side, but the drug molecules in the outer layer quercetin-loaded Eudragit L-100 (Q/EL/PEG) membrane moved after absorbing a large amount of water. The drug release behavior of multilayer wound dressing mainly followed the Korsmeyer-Peppas model. This multifunctional electrospun membrane could rapidly drive the biofluid outflow, effectively block the invasion of external contaminants and continuously release anti-inflammatory drugs, without any obvious cytotoxicity to mouse fibroblast cells. Hence, the above results indicate the excellent therapeutic potential of the proposed biomaterial as a wound dressing for diabetic patients.

One-Step Construction of the Positively/Negatively Charged Ultrathin Janus Nanofiltration Membrane for the Separation of Li+ and Mg2

To coordinate the trade-off between the separation and permeation of the nanofiltration membrane for the separation of Mg²⁺/Li⁺, we regulated poly(ethyleneimine)/piperazine interface polymerization parameters to construct a positively/negatively charged ultrathin Janus nanofiltration membrane at a free aqueous-organic interface. At the optimized interfacial polymerization parameters, 0.03 wt % of piperazine reacted with trimethylbenzene chloride prior to poly(ethyleneimine), forming a primary polyamide layer with fewer defects or limiting large-scale defects of the polyamide layer. The controlled subsequent reaction of poly(ethyleneimine) and trimethylbenzene chloride results in a Janus nanofiltration membrane, with one side enriched with the carboxyl groups, the other side enriched with the amine groups, and a dense polyamide structure in the middle. Under the optimum conditions, the positive potential of the rear surface of the prepared membrane was 14.57 mV, and the water contact angle reached 71.31°, while the negative potential of the front surface was -25.48 mV, and the water contact angle was 12.93°, confirming a Janus membrane with opposite charges and large hydrophilicity differences in the front and rear surfaces. With a high cross-linking degree, a 40 nm thick polyamide layer is 29.09% more thinner than the traditional polyamide membrane. The ultrathin Janus nanofiltration membrane showed an excellent separation factor (S_Li,Mg of 18.26), stability, and water permeability flux (10.6 L·m^-2·h^-1·bar^-1). The rejections to MgCl₂, CaCl₂, MgSO₄, and Na₂SO₄ are measured above 90% at a nearly constant permeability of 10.6 L·m^-2·h^-1·bar^-1, particularly stable rejections to MgCl₂ and Na₂SO₄.

Molecularly Imprinted Membrane Produced by Electrospinning for β-Caryophyllene Extraction

Molecularly imprinted membrane of β-caryophyllene (MIM-βCP) was fabricated incorporating β-caryophyllene molecularly imprinted polymer nanoparticles (βCP-NP) into polycaprolactone (PCL) fibers via electrospinning. The βCP-NP were synthesized by precipitation polymerization using the βCP as a template molecule and acrylic acid as a functional monomer in the proportion of 1:4 mol, respectively. Atomic force microscopy images and X-ray diffraction confirmed the nanoparticles' incorporation into MIM-βCP. MIM-βCP functionalization was evaluated by gas chromatography. The binding capacity was 1.80 ± 0.05 μmol/cm², and the selectivity test was performed with a mixing solution of βCP and caryophyllene oxide, as an analog compound, that extracted 77% of the βCP in 5 min. The electrospun MIM-βCP can be used to detect and extract the βCP, applications in the molecular sieve, and biosensor production and may also contribute as an initial methodology to enhance versatile applications in the future, such as in the treatment of skin diseases, filters for extraction, and detection of βCP to prevent counterfeiting of commercial products, and smart clothing with insect-repellent properties.

Review on the Development and Application of Directional Water Transport Textile Materials

Moisture (sweat) management in textile products is crucial to regulate human thermo-physiological comfort. Traditional hydrophilic textiles, such as cotton, can absorb sweat, but they retain it, leading to undesired wet adhesion sensation and even excessive cooling. To address such issues, the development of functional textiles with directional water transport (DWT) has garnered great deal of interest. DWT textile materials can realize directional water transport and prevent water penetration in the reverse direction, which is a great application for sweat release in daily life. In this review article, the mechanism of directional water transport is analyzed. Then, three key methods to achieve DWT performance are reviewed, including the design of the fabric structure, surface modification and electrospinning. In addition, the applications of DWT textile materials in functional clothing, electronic textiles, and wound dressing are introduced. Finally, the challenges and future development trends of DWT textile materials in the textile field are discussed.