Temperature-adjustable F-carbon nanofiber/carbon fiber nanocomposite fibrous masks with excellent comfortability and anti-pathogen functionality

Abstract

Wearing surgical masks remains the most effective protective measure against COVID-19 before mass vaccination, but insufficient comfortability and low antibacterial/antiviral activities accelerate the replacement frequency of surgical masks, resulting in large amounts of medical waste. To solve this problem, we report new nanofiber membrane masks with outstanding comfortability and anti-pathogen functionality prepared using fluorinated carbon nanofibers/carbon fiber (F-CNFs/CF). This was used to replace commercial polypropylene (PP) nonwovens as the core layer of face masks. The through-plane and in-plane thermal conductivity of commercial PP nonwovens were only 0.12 and 0.20 W/m K, but the F-CNFs/CF nanofiber membranes reached 0.62 and 5.23 W/m K, which represent enhancements of 380% and 2523%, respectively. The surface temperature of the PP surgical masks was 23.9 ℃ when the wearing time was 15 min, while the F-CNFs/CF nanocomposite fibrous masks reached 27.3 ℃, displaying stronger heat dissipation. Moreover, the F-CNFs/CF nanofiber membranes displayed excellent electrical conductivity and produced a high-temperature layer that killed viruses and bacteria in the masks. The surface temperature of the F-CNFs/CF nanocomposite fibrous masks reached 69.2 ℃ after being connected to a portable power source for 60 s. Their antibacterial rates were 97.9% and 98.6% against E. coli and S. aureus, respectively, after being connected to a portable power source for 30 min.

Keywords: Anti-pathogen functionality; COVID-19; Electrothermal conversion; Face masks; Wearing comfortability.

Graphical abstract

Fig. 1

Preparation process of the F-CNFs/CF nanofiber membranes.

Fig. 2

(a) FTIR spectra of the pure CNFs and acid-washed CNFs. (b) FTIR spectra of the pure CF, CF membrane, and CNFs/CF. (c) FTIR spectra of the F-CNFs/CF. (d) Full-scan XPS spectra of pristine CF, CNFs/CF, and F-CNFs/CF-4. (e) Enlargement of the Si spectrum. (e) N 1 s core-level spectra of pristine h-BN. (f) C 1 s core-level spectra of pristine CF. (g) C 1 s core-level spectra of CNFs/CF. (h) C 1 s core-level spectra of pristine F-CNFs/CF-4. (i) Hydrophilic test of CNFs/CF. (j) Hydrophilic test of F-CNFs/CF nanofiber membranes. (k) Contact angles of CF membrane and F-CNFs/CF nanofiber membranes.

Fig. 3

(a) Microstructure of commercial PP nonwovens; (a’) Fiber diameter distribution of commercial PP nonwoven; (a’’) Pore diameter distribution of commercial PP nonwovens. (b) Microstructure of the CF membrane; (b’) Fiber diameter distribution of the CF membrane; (b’’) Pore diameter distribution of the CF membrane; (c) and (c’) Microstructure of F-CNFs/CF-4 nanofiber membranes; (c’’) Pore diameter distribution of F-CNFs/CF-4 nanofiber membranes. (d) The PM_2.5 removal efficiency of commercial PP nonwovens, CF membrane, and F-CNFs/CF nanofiber membranes. (e) The air permeability of commercial PP nonwovens, CF membrane, and F-CNFs/CF nanofiber membranes. (f) The PM_2.5 removal efficiency of the F-CNFs/CF-4 nanofiber membranes after five recycling usages. (g) Tensile strength of commercial PP nonwovens, CF membrane, and F-CNFs/CF nanofiber membranes.

Fig. 4

(a) Thru-plane thermal conductivity of commercial PP nonwovens, CF membrane, and F-CNFs/CF nanofiber membranes. (b) In-plane thermal conductivity of commercial PP nonwovens, CF membrane, and F-CNFs/CF nanofiber membranes. (c) Surface morphology of CF membrane. (d) and (d’) Surface morphology of F-CNFs/CF-4 nanofiber membranes. (e) and (e’) Cross-section morphology of CF membrane. (e’’) Simplified model of CF membrane. (f) and (f’) Cross-section morphology of F-CNFs/CF-4 nanofiber membranes. (f’’) Simplified model of F-CNFs/CF-4 nanofiber membranes.

Fig. 5

(a) Schematic diagram of the structure of the F-CNFs/CF nanocomposite fibrous masks. (b) Thermal images of commercial PP surgical masks and F-CNFs/CF nanocomposite fibrous masks. (c) Surface temperatures of commercial PP surgical masks and F-CNFs/CF nanocomposite fibrous masks at different times.

Fig. 6

(a) The resistance of F-CNFs/CF-4 nanofiber membranes measured by a multimeter; (b) The resistance of F-CNFs/CF-4 nanofiber membranes measured by voltammetry; (c) Electrical conductivity of CF membrane and F-CNFs/CF-4 nanofiber membranes; (d) Transforming electricity into heat in the F-CNFs/CF nanocomposite fibrous masks by connecting them to a portable power source; (e) Surface temperature of F-CNFs/CF nanocomposite fibrous masks after connecting to a portable power source; (f) Schematic diagram of the antiviral principle of F-CNFs/CF nanocomposite fibrous masks.

Fig. 7

(a) Schematic diagram of antibacterial experiment of F-CNFs/CF nanocomposite fibrous masks; (b) Image of heated bacterial solution; (c) IR thermal images of the antibacterial experiment of F-CNFs/CF nanocomposite fibrous masks; (d) Images of the distributions of E. coli and S. aureus colonies on nutrient agar solid plates.

Fig. 8

(a) Temperature test and (b) data of F-CNFs/CF nanocomposite fibrous masks connected to a portable power source in a low-temperature environment. (c) IR thermal images of the F-CNFs/CF nanocomposite fibrous masks after connecting to a portable power source in a low-temperature environment. (d) Diagram of F-CNFs/CF nanocomposite fibrous mask resistance during electrothermal measurements. (e) Temperature of the F-CNFs/CF nanocomposite fibrous mask as a function of applied resistance. (f) IR thermal images of F-CNFs/CF nanocomposite fibrous masks at different resistance values.