Multifunctional Filter Membranes Based on Self-Assembled Core–Shell Biodegradable Nanofibers for Persistent Electrostatic Filtration through the Triboelectric Effect

Abstract

The massive production of polymer-based respiratory masks during the COVID-19 pandemic has rekindled the issue of environmental pollution from nonrecyclable plastic waste. To mitigate this problem, conventional filters should be redesigned with improved filtration performance over the entire operational life while also being naturally degradable at the end. Herein, we developed a functional and biodegradable polymeric filter membrane consisting of a polybutylene adipate terephthalate (PBAT) matrix blended with cetyltrimethyl­ammonium bromide (CTAB) and montmorillonite (MMT) clay, whose surface properties have been modified through cation exchange reactions for good miscibility with PBAT in an organic solvent. Particularly, the spontaneous evolution of a partial core–shell structure (i.e., PBAT core encased by CTAB-MMT shell) during the electrospinning process amplified the triboelectric effect as well as the antibacterial/antiviral activity that was not observed in naive PBAT. Unlike the conventional face mask filter that relies on the electrostatic adsorption mechanism, which deteriorates over time and/or due to external environmental factors, the PBAT@CTAB-MMT nanofiber membrane (NFM)-based filter continuously retains electrostatic charges on the surface due to the triboelectric effect of CTAB-MMT. As a result, the PBAT@CTAB-MMT NFM-based filter showed high filtration efficiencies (98.3%, PM0.3) even at a low differential pressure of 40 Pa or less over its lifetime. Altogether, we not only propose an effective and practical solution to improve the performance of filter membranes while minimizing their environmental footprint but also provide valuable insight into the synergetic functionalities of organic–inorganic hybrid materials for applications beyond filter membranes.

Electrospun nanofibers for medical face mask with protection capabilities against viruses: State of the art and perspective for industrial scale-up

“…After sterilization procedure, the residual contaminant that adhered the fibers surface were easily removed by means of water immersion and further air blowing, thus making it reusable. It is important to note that these biodegradable TENG showed comparable and in some cases higher QF values to those reported for other inorganic polymer based devices ( Table 4 ) as well as a better biodegradation rate when they are either buried in composting soil or exposed to optimal degradation condition [ 259 , 260 ]. In view of their importance for innovative biomedical application, many of these biodegradable polymers are available on the market nowadays and can be easily dissolved into solution to be used for scalable manufacturing process [ 128 , 262 , 263 ].…”

“…12 (a) A picture for the charge-trapping mechanism of HPFM electrospun membrane; (b) surface potential variation as function of time obtained for the HPFM system, FEP electret nanofibrous membrane, and PTFE electret nanofibrous membrane; (c) thermally stimulating discharge current spectra (left) and corresponding KPFM images measured for the nanofibers of FFM, PFM, and HPFM (right); adapted with permission from [ 258 ]. (d) Filter efficiency evaluation obtained or the PBAT/CTAB/MMT and PBAT triboelectric membranes; (e) a comparison between the Inactivation rates of both influenza virus (left) and Coronavirus (right) obtained for PBAT/CTAB, PBAT, and PBAT/CTAB/MMT; adapted with permission from [ 260 ]. (f) A picture of a face mask made of electrospun piezoelectric PLLA nanofibers showing SEM images for the combined effect in PM capturing due to mechanical sieving and piezoelectrically enhanced electrostatic adsorption; (g) decontamination of the PLLA air filter from P. aeruginosa (gram-negative) and S. aureus (gram-positive) bacteria via ultrasound stimulation; adapted with permission from [ 259 ].…”

“…The smart face mask designed by Yujang Cho et al . based on biodegradable polybutylene adipate terephthalate (PBAT) electrospun filter, functionalized with ecofriendly nanoclay mineral montmorillonite (MMT), and cetyltrimethylammonium bromide (CTAB) surfactant, provided higher filtration performance for PM 0.3 , compared to commercial face mask [ 260 ] ( Fig. 12 d).…”

Bioelectrets in Electrospun Bimodal Poly(lactic acid) Fibers: Realization of Multiple Mechanisms for Efficient and Long-Term Filtration of Fine PMs

“…By decreasing the fiber diameter, the physical interception efficiency and the air permeability could be significantly elevated. 22,23 To capture particles below PM 0.3 and deactivate viruses, an elevated surface potential of PLA fibrous membranes is needed for pollutant removal utilizing electrostatic adsorption between the fibers and PMs. 24,25 The potential utilization of HABE as an electret material could seamlessly integrate the strengths of physical interception and electrostatic trapping, which will effectively capture contaminants such as PM 0.3−10 .…”

“…Typically, the limited physical interception of the fibrous membrane intercepts the larger particles above PM 0.3 . By decreasing the fiber diameter, the physical interception efficiency and the air permeability could be significantly elevated. , To capture particles below PM 0.3 and deactivate viruses, an elevated surface potential of PLA fibrous membranes is needed for pollutant removal utilizing electrostatic adsorption between the fibers and PMs. , The potential utilization of HABE as an electret material could seamlessly integrate the strengths of physical interception and electrostatic trapping, which will effectively capture contaminants such as PM 0.3–10 . The electrospinning process produces dipole orientation of PLA with electrostatic fields, and deep charge traps may occur at the HABE–PLA interfaces, facilitating the electrostatic adsorption of PMs .…”