Radiative Thermal Management in Face Masks with a Micro/Nanofibrous Filter.

Micro/nanofiber-based face masks are recommended as personal protective equipment (PPE) against particulate matter (PM), especially PM0.3. Ensuring thermal comfort in daily use face masks is essential in many situations. Here, radiative thermal management is introduced into face masks to elevate the user comfort. An interlayered poly(lactic acid) (PLA) micro/nanofibrous filter effectively captures PM0.3 (99.69%) with minimal pressure drop (49 Pa). Thermal regulation is accomplished by controlling the mid-infrared (MIR) emissivity of the face mask's outer surface. Cooling face masks feature cotton nonwovens with high MIR emissivity (90.7%) for heat dissipation, while warming face masks utilize perforated Al/PE films with minimal MIR emissivity (10.7%) for warmth retention. Skin temperature measurements indicate that the skin covered by the cooling face mask could be 1.1 °C lower than that covered by the 3M face mask, while the skin covered by the warming face mask could be 1.3 °C higher than that covered by the 3M face mask.

Highly Efficient Fabrication of Biomimetic Nanoscaled Tendrils for High-Performance PM0.3 Air Filters.

Particulate matter pollution has become a serious public health issue, especially with the outbreak of new infectious diseases. However, most existing air filtration materials face challenges such as being too bulky, having high resistance, and a trade-off between filtration efficiency and air permeability. Here, a unique electro-blown spinning technique is used to prepare an air filter made of biomimetic nanoscaled tendril nonwovens (Nano-TN). The introduction of an airflow field significantly increases the whipping frequency and the strain mismatch of composite jets, achieving large-scale and highly efficient preparation of Nano-TN. The resultant Nano-TN has an ultrahigh porosity (97%) and a small pore size (2.9 µm). At the same filtration level, its air resistance is 37% lower than that of traditional straight nanofibrous nonwovens and has a higher dust-holding capacity. Moreover, compared with traditional three-dimensional air filters, the Nano-TN filter is thinner, offering tremendous application prospects in various environmental purification and personal protection fields.

Tracing the Flu Symptom Progression via a Smart Face Mask.

Respiration and body temperature are largely influenced by the highly contagious influenza virus, which poses persistent global public health challenges. Here, we present a wireless all-in-one sensory face mask (WISE mask) made of ultrasensitive fibrous temperature sensors. The WISE mask shows exceptional thermosensitivity, excellent breathability, and wearing comfort. It offers highly sensitive body temperature monitoring and respiratory detection capabilities. Capitalizing on the advances in the Internet of Things and artificial intelligence, the WISE mask is further demonstrated by customized flexible circuitry, deep learning algorithms, and a user-friendly interface to continuously recognize the abnormalities of both the respiration and body temperature. The WISE mask represents a compelling approach to tracing flu symptom progression in a cost-effective and convenient manner, serving as a powerful solution for personalized health monitoring and point-of-care systems in the face of ongoing influenza-related public health concerns.

Multi-layered micro/nanofibrous nonwovens for functional face mask filter.

The worldwide COVID-19 pandemic has led to an attention on the usage of personal protective face masks. However, the longevity and safety of the commercial face masks are limited due to the charge dissipation of the electret meltblown nonwovens, which are dominate in the face mask filters. Herein, we design a type of multi-layer structured nonwovens using meltblowing and electrospinning technologies. The complex nonwovens involving meltblown and electrospun fibers are designed to possess multilevel fiber diameters and pore sizes. The micro/nanofibers with porous and wrinkled surface morphologies can well capture particulate matters (PMs), and the multilevel pore sizes contribute to low air resistance under high filtration efficiency. Airflow field simulation was carried out to understand the pressure distribution within the nonwovens in the filtration process. Meanwhile, by adding Ag nanoparticles (AgNPs) as additives, the nonwovens exhibit excellent antibacterial performance. The resultant nonwovens exhibit filtration efficiency of 99.1% for PM0.3 and low pressure drop of 105 Pa under the 10.67 cm/s inlet air velocity, and antibacterial rate of > 99.99% for Escherichia coli. These performances and functions make the designed complex nonwovens a promising filter core for face masks. Electronic Supplementary Material: Supplementary material (Fig. S1. The filtration efficiencies of a brand of surgical mask changes with the storage time under the condition of 100% humidity. Fig. S2. The FE-SEM images of the fibers after blocking PMs. Fig. S3. Illustration of 3D structure models of the nonwovens. Fig. S4. Diameter distribution of AgNPs. Table S1. The structure parameters and filtration performances of the PP-M fibers with and without pores and wrinkles. Table S2. Filtration performance of PP-M/PLA-M/PLA-N nonwovens and commercial face masks. Table S3. The structural parameters for the nonwovens. Table S4. The filtration efficiencies and pressure drops of the PP, PE spunbonded nonwovens, and PP-M/PLA-M/PLA-N@AgNPs nonwovens) is available in the online version of this article at 10.1007/s12274-022-4350-2.

Multi-functional air filters with excellent flame retardancy and fire-warning capability.

High fire-safe air filters are indispensable for indoor environments, such as vehicle interior, fresh air filtration system, and window screens. However, it is still challenging to afford both excellent flame retardancy and rapid fire-warning capability in air filters. In this study, we fabricate a type of high-efficient fiber filters with combined flame-retardant and fire-warning performance. Nanofibers with a specific tri-layer structure are designed to incorporate Polyacrylonitrile (PAN) matrix and two functional components, flame retardant ammonium polyphosphate (APP) and amino-functionalized carbon nanotube (A-CNTs). The resultant PAN/CNTs/APP fiber filters have high PM2.5-10 capture efficiency of > 99.99%. The filters can not be burnt in vertical burning test and exhibit high limiting oxygen index value of 30.9%. Moreover, the resultant PAN/CNTs/APP fiber filters achieve short fire-warning response time (∼5s) when encounters fire. This work offers a facile and cost-effective approach to fabricate multifunctional air filters, and shows promising applications in vehicle interior, firefighting, fresh air filtration and building materials.

Zein adsorbents with micro/nanofibrous membrane structure for removal of oils, organic dyes, and heavy metal ions in aqueous solution.

Developing multi-functional media for effectively removing different contaminants coexisted in wastewater system is highly desired. Herein, zein, a natural protein possessing abundant functional groups in molecule, is chosen to be fabricated into micro/nanofibrous membranes as adsorbents and separation media. Zein fibers with novel groove ribbon structures, which possess better structural characteristics, are designed for obtaining good adsorption performance. The adsorption performances of zein fiber membranes are evaluated. The results show that zein fiber membranes have the adsorption capacities up to 94 g/g for motor oil, 168 mg/g for Congo red, and 189 mg/g for Pb2+ ion for 1000 mg/L initial solution concentration, showing considerable competitiveness as compared with the reported adsorbents. The zein membrane with groove ribbon fiber morphology exhibits optimal adsorption capability and can be attractive multi-functional separation media.

Micro/nanofibrous nonwovens with high filtration performance and radiative heat dissipation property for personal protective face mask.

The COVID-19 pandemic and airborne particulate matter (PM) pollution have posed a great threat to human health. Personal protective face masks have become an indispensable protective equipment in our daily lives. However, wearing conventional face masks for a long time cause swelter and discomfort on the face. Introducing thermal comfort into personal protective face masks becomes desirable. Herein, face masks that show excellent filtration performance and radiative heat dissipation effect are successfully designed and prepared by electrospining Nylon-6 (PA) nanofibers onto polyethylene (PE) meltblown nonwovens. The resultant PE/PA nonwovens have high PM filtration efficiency (>99%) with a low pressure drop (<100 Pa). Moreover, taking the advantage of the property of PE, the designed face mask posses high mid-infrared (mid-IR) transmittance and brings about high radiative cooling power, resulting in effective heat dissipation performance. This face mask design may provides new insights into the development of thermal comfort materials for personal protection.

Multifunctional, Waterproof, and Breathable Nanofibrous Textiles Based on Fluorine-Free, All-Water-Based Coatings.

Developing environmentally benign, multifunctional waterproof and breathable membranes (WBMs) is of great importance but still faces enormous challenges. Here, an environmentally benign fluorine-free, ultraviolet (UV) blocking, and antibacterial WBM with a high level of waterproofness and breathability is developed on a large scale by combining electrospinning and step-by-step surface coating technology. Fluorine-free water-based alkylacrylates with long hydrocarbon chains were coated onto polyamide 6 fibrous membranes to construct robust hydrophobic surfaces. The subsequent titanium dioxide nanoparticle emulsion coating prominently decreased the maximum pore size, leading to higher water resistance, endowing the membranes with efficient UV-resistant and antibacterial properties. The resulting fibrous membranes possessed excellent waterproofness of 106.2 kPa, exceptional breathability of 10.3 kg m-2 d-1, a significant UV protection factor of 430.5, together with a definite bactericidal efficiency of 99.9%. We expect that this methodology for construction of environmentally benign and multifunctional WBMs will shed light on the material design, and the prepared membranes could implement their promising applications in covering materials, outdoor equipment, protective clothing, and high-altitude garments.