Ultrasensitive and Recyclable Multifunctional Superhydrophobic Sensor Membrane for Underwater Applications, Weather Monitoring, and Wastewater Treatment

Sustainable nanofibrous membranes for air filtration, water purification and oil removal

The increasing demand for sustainable solutions to address environmental and energy challenges has driven the development of advanced materials. Among them, nanofibrous membranes have emerged due to their high surface area, tunable porosity and versatile mechanical properties. However, traditional nanofibrous membranes, made from petroleum-based synthetic polymers, pose significant environmental concerns due to their non-biodegradability and reliance on fossil resources. This paper reviews recent advancements in the development of sustainable nanofibrous membranes, focusing on the use of biobased and biodegradable materials, and circular design approaches aimed at reducing environmental impact throughout the membrane life cycle. Challenges associated with improving the mechanical strength and stability of biopolymer-based nanofibers and expanding application areas are discussed. By highlighting strategies to overcome these limitations, this review aims to provide insights into the future direction of sustainable nanofibrous membranes, paving the way for their broader adoption in eco-friendly technological solutions.

Electrospun multifunctional nanofibers for advanced wearable sensors

The multifunctional extension of fiber-based wearable sensors determines their integration and sustainable development, with electrospinning technology providing reliable, efficient, and scalable support for fabricating these sensors. Despite numerous studies on electrospun fiber-based wearable sensors, further attention is needed to leverage composite structural engineering for functionalizing electrospun fibers. This paper systematically reviews the research progress on fiber-based multifunctional wearable sensors in terms of design concept, device fabrication, mechanism exploration, and application potential. Firstly, the basics of electrospinning are briefly introduced, including its development, principles, parameters, and material selection. Tactile sensors, as crucial components of wearable sensors, are discussed in detail, encompassing their performance parameters, transduction mechanisms, and preparation strategies for pressure, strain, temperature, humidity, and bioelectrical signal sensors. The main focus of the article is on the latest research progress in multifunctional sensing design concepts, multimodal decoupling mechanisms, sensing mechanisms, and functional extensions. These extensions include multimodal sensing, self-healing, energy harvesting, personal thermal management, EMI shielding, antimicrobial properties, and other capabilities. Furthermore, the review assesses existing challenges and outlines future developments for multifunctional wearable sensors, highlighting the need for continued research and innovation.

Superhydrophobic wearable sensor: fabrication, application, and perspective

Wearable sensors have attracted considerable interest due to their ability to detect a variety of information generated by human physiological activities through physical and chemical means. The performance of wearable sensors is limited by their stability, and endowing wearable sensors with superhydrophobicity is one of the means to enable them to maintain excellent performance in harsh environments. This review emphasizes the imperative progress in flexible superhydrophobic sensors for wearable devices. Besides, the wettability principle and the mechanism of wearable sensors are briefly introduced to propose the combination of superhydrophobicity and wearable sensors. Next, superhydrophobic substrates for wearable sensors, including but not limited to, polydimethylsiloxane, polyurethane, gel, rubber, and fabric, are described in depth, and also the respective fabrication processes and performances. Moreover, the utility of superhydrophobic wearable sensors in a normal intelligent environment is described, highlighting their application in monitoring physiological signals, such as physical movement, pulse, vibration, temperature, perspiration, respiration, and so on. Finally, this review evaluates the challenges and dilemmas that wearable sensors must be overcome for further development and improve the functional performance of wearable sensors, paving the way for their expansion into advanced wearable sensing systems.

Superhydrophobic stretchable sensors based on interfacially self-assembled carbon nanotube film for self-sensing drag-reduction shipping

Multifunctional flexible electronics integrated with superhydrophobicity and flexible sensing can greatly promote broader applications. However, the hierarchical roughness morphology of superhydrophobic surfaces is vulnerable to complex mechanical deformations of stretchable sensors leading to degradation of hydrophobic properties, so constructing robust superhydrophobic stretchable sensors remains challenging. Herein, we propose a facile strategy to fabricate superhydrophobic stretchable sensors based on self-assembled carbon nanotube (CNT) films at the air-water interface. The customizable functions of superhydrophobic stretchable sensors can be achieved by controlling the combination of the CNT film and polydimethylsiloxane (PDMS) through a simple and efficient interfacial transferring strategy. Even under large mechanical deformations, the developed sensors can present excellent robustness and superhydrophobicity with a water contact angle of 150.9° at 80% strain. As a proof-of-concept, this work demonstrates their potential application in self-sensing drag-reduction shipping, which is expected to realize greener, more sustainable and safer aquatic transportation.

Hydrophobic TPU/CNTs-ILs Ionogel as a Reliable Multimode and Flexible Wearable Sensor for Motion Monitoring, Information Transfer, and Underwater Sensing

Ionogel-based sensors have gained widespread attention in recent years due to their excellent flexibility, biocompatibility, and multifunctionality. However, the adaptation of ionogel-based sensors in extreme environments (such as humid, acidic, alkaline, and salt environments) has rarely been studied. Here, thermoplastic polyurethane/carbon nanotubes-ionic liquids (TPU/CNTs-ILs) ionogels with a complementary sandpaper morphology on the surface were prepared by a solution-casting method with a simple sandpaper as the template, and the hydrophobic flexible TPU/CNTs-ILs ionogel-based sensor was obtained by modification using nanoparticles modified with cetyltrimethoxysilane. The hydrophobicity improves the environmental resistance of the sensor. The ionogel-based sensor exhibits multimode sensing performance and can accurately detect response signals from strain (0-150%), pressure (0.1-1 kPa), and temperature (30-100 °C) stimuli. Most importantly, the hydrophobic TPU/CNTs-ILs ionogel-based sensors can be used not only as wearable strain sensors to monitor human motion signals but also for information transfer, writing recognition systems, and underwater activity monitoring. Thus, the hydrophobic TPU/CNTs-ILs ionogel-based sensor offers a new strategy for wearable electronics, especially for applications in extreme environments.

Research Progress and Application of Multimodal Flexible Sensors for Electronic Skin

In recent years, wearable electronic skin has garnered significant attention due to its broad range of applications in various fields, including personal health monitoring, human motion perception, human-computer interaction, and flexible display. The flexible multimodal sensor, as the core component of electronic skin, can mimic the multistimulus sensing ability of human skin, which is highly significant for the development of the next generation of electronic devices. This paper provides a summary of the latest advancements in multimodal sensors that possess two or more response capabilities (such as force, temperature, humidity, etc.) simultaneously. It explores the relationship between materials and multiple sensing capabilities, focusing on both active materials that are the same and different. The paper also discusses the preparation methods, device structures, and sensing properties of these sensors. Furthermore, it introduces the applications of multimodal sensors in human motion and health monitoring, as well as intelligent robots. Finally, the current limitations and future challenges of multimodal sensors will be presented.

Electrospun green-emitting La2O2CO3:Tb3+ nanofibers and La2O2CO3:Tb3+/Eu3+ nanofibers with white-light emission and color-tuned photoluminescence

Color-tuned luminescence and white-light emission materials have attracted much attention owing to their broad application prospects. Generally, Tb³⁺ and Eu³⁺ co-doped phosphors have color-tuned luminescence, but white-light emission is rarely achieved. In this work, color-tunable photoluminescence and white light emission are achieved in Tb³⁺ and Tb³⁺/Eu³⁺ doped monoclinic-phase La₂O₂CO₃ one-dimensional (1D) nanofibers synthesized by electrospinning united with succedent strictly controlling calcination procedure. The prepared samples own excellent fibrous morphology. La₂O₂CO₃:Tb³⁺ nanofibers are the superior green-emitting phosphors. To obtain 1D nanomaterials with color-tunable fluorescence, particularly those with white-light emission, Eu³⁺ ions are further selected and doped into La₂O₂CO₃:Tb³⁺ nanofibers to obtain La₂O₂CO₃:Tb³⁺/Eu³⁺ 1D nanofibers. The major emission peaks of La₂O₂CO₃:Tb³⁺/Eu³⁺ nanofibers at 487, 543, 596 and 616 nm are attributed to ⁵D₄→⁷F₆ (Tb³⁺), ⁵D₄→⁷F₅ (Tb³⁺), ⁵D₀→⁷F₁ (Eu³⁺) and ⁵D₀→⁷F₂ (Eu³⁺) energy levels transitions under 250-nm (for Tb³⁺ doping) and 274-nm (for Eu³⁺ doping) UV light excitation, respectively. At different wavelengths excitation, La₂O₂CO₃:Tb³⁺/Eu³⁺ nanofibers with excellent stability achieve color-tuned fluorescence and white-light emission with the help of energy transfer from Tb³⁺ to Eu³⁺ and tuning the doping concentration of Eu³⁺ ions. Formative mechanism and fabrication technique of La₂O₂CO₃:Tb³⁺/Eu³⁺ nanofibers are advanced. The design concept and manufacturing technique developed in this work may offer fresh insights for synthesizing other 1D nanofibers doped with rare earth ions to tune emitting fluorescent colors.

In Situ Polymerized MXene/Polypyrrole/Hydroxyethyl Cellulose-Based Flexible Strain Sensor Enabled by Machine Learning for Handwriting Recognition

Flexible strain sensors have significant progress in the fields of human-computer interaction, medical monitoring, and handwriting recognition, but they also face many challenges such as the capture of weak signals, comprehensive acquisition of the information, and accurate recognition. Flexible strain sensors can sense externally applied deformations, accurately measure human motion and physiological signals, and record signal characteristics of handwritten text. Herein, we prepare a sandwich-structured flexible strain sensor based on an MXene/polypyrrole/hydroxyethyl cellulose (MXene/PPy/HEC) conductive material and a PDMS flexible substrate. The sensor features a wide linear strain detection range (0-94%), high sensitivity (gauge factor 357.5), reliable repeatability (>1300 cycles), ultrafast response-recovery time (300 ms), and other excellent sensing properties. The MXene/PPy/HEC sensor can detect human physiological activities, exhibiting excellent performance in measuring external strain changes and real-time motion detection. In addition, the signals of English words, Arabic numerals, and Chinese characters handwritten by volunteers measured by the MXene/PPy/HEC sensor have unique characteristics. Through machine learning technology, different handwritten characters are successfully identified, and the recognition accuracy is higher than 96%. The results show that the MXene/PPy/HEC sensor has a significant impact in the fields of human motion detection, medical and health monitoring, and handwriting recognition.