Hierarchically heterogeneous interface structuring strategy for microenvironment-regulating and self-decontaminating biodegradable meta-membranes

Abstract

Precise functionalization of heterogeneous interfaces in nanofibers is essential for advanced personal protective membranes. Here, we demonstrate a hierarchically heterogeneous interface structuring (HHIS) strategy to fabricate microenvironment-regulating and self-decontaminating meta-membranes (MRSD-PLA) by embedding zeolitic imidazolate framework-8 (ZIF-8) nanocrystals within poly(lactic acid) (PLA) fibers and anchoring F-TiO₂ nanoblocks on their surfaces, creating an electronegativity contrast that directs electron migration and charge redistribution. ZIF-8 of porosity and electroactivity could enable charge capture/storage and trans-membrane transport (water vapor transmission rate: 4018 g·m⁻²·d⁻¹; air permeability > 60 mm·s⁻¹ at 100 Pa). Combined with the hydrophobicity and self-cleaning capability from F-TiO₂, a sustained charge migration establishes a closed-loop capture-storage-regeneration cycle. This results in self-powered sensitive monitoring and a high PM_0.3 filtration efficiency of 99.3% yet a low pressure drop of 51.9 Pa (quality factor: 0.11 Pa⁻¹). Moreover, MRSD-PLA inhibit bacterial growth and balance robust mechanical strength with biodegradability, showcasing great potential for high-performance personal protection.

The authors developed biodegradable meta-membranes that regulate the skin microenvironment, self-decontaminate, and maintain high air purification efficiency even under humidity were developed, offering a sustainable solution for personal protective equipment.

Introduction

Multifunctional personal protective equipment is of critical importance for healthcare, aerospace, and specialized operations^1,2. However, conventional protective materials often fail to integrate high protective performance, physiological comfort, and environmental sustainability. For instance, most high-efficiency barriers rely on high-basis-weight nonwovens or dense coatings, which severely restricts air and moisture permeability^3,4. Similarly, electret materials experience significant charge decay in high-humidity environments, leading to a substantial decline in filtration efficiency⁵. Furthermore, the massive disposal of single-use protective gear poses escalating ecological threats. To address these interconnected challenges, developing advanced intelligent protective materials with multifunctional capabilities has become a critical focus in materials science and engineering.

A stable human microenvironment at the skin‒textile interface, characterized by moisture-thermal balance and cleanliness, is critical for the wearing comfort, health safety, and functional efficacy of protective membranes^6,7. While dense structures can provide barrier properties against pollutants, they often severely restrict air permeability and moisture transport, compromising microenvironmental stability^2,8. Conversely, porous breathable membranes, which are often inherently hydrophilic and possess low-surface roughness, are prone to liquid penetration and pollutant adhesion, lacking self-cleaning capability⁹. In this context, nanofiber membranes offer a promising platform for simultaneous microenvironment regulation and hydrophobic self-cleaning, owing to their high specific surface area, tunable porosity, and facile surface modifiability. Their interconnected porous networks facilitate efficient transport of moisture vapor and air¹⁰. Through precise control of porosity and pore size distribution, they can effectively manage metabolic heat and moisture, thus contributing to maintain moisture-thermal balance at the skin surface. However, the performance limitations of single-component nanofiber membranes hinder their ability to meet the multiple demands of complex application scenarios¹¹.

Recently, nanofiber-based heterogeneous interface engineering has become a pivotal strategy for enhancing the performance of multifunctional nanocomposites. Nanofibers serve as ideal structural scaffolds for constructing hierarchical heterogeneous interfaces with distinct component gradients, controllable microtopography, and tunable electronic structures^12,13. These interfaces are engineered by precisely regulating the interactions, geometry, and chemical environments of components within the fiber core, at its surface, or between adjacent fibers^14,15, offering valuable insights for the design of advanced protective membranes¹⁶. For example, interfaces between metal-organic frameworks (MOFs) and polymers leverage MOF porosity for enhanced molecular transport and utilize coordination interactions for charge storage^17,18. Similarly, surface modification of metal oxides at fibers can introduce tailored functionalities at the interfaces^19,20. However, current studies predominantly focus on single-component systems or isolated interface designs, lacking a systematic strategy to construct truly hierarchical heterogeneous architectures. The absence of multiscale and hierarchical organization leads to an inefficient allocation of functionalities, such as microenvironment regulation, self-decontamination, and high-performance protection, across different interfacial levels^21,22, which in turn compromises functional synergy and limits performance in challenging protection scenarios.

Herein, we disclose a hierarchically heterogeneous interface structuring (HHIS) strategy for fabricating microenvironment-regulating and self-decontamination poly(lactic acid) (MRSD-PLA) meta-membranes, thereby removing the classic trade-off between structural integrity and functional performance in personal protective membranes. These MRSD-PLA meta-membranes exhibit a hierarchical structure with integrated functionality, arising from the multiscale organization and interfacial coupling of distinct phases. Using biodegradable PLA as the structural scaffold, our HHIS strategy involves embedding highly porous and electroactive zeolitic imidazolate framework-8 (ZIF-8) nanocrystals within the individual fibers. ZIF-8 composed of zinc ions coordinated with 2-methylimidazole ligands features a robust microporous framework. The ordered channels enable directional transport of small molecules (e.g., water vapor and air), allowing for effective regulation of temperature and humidity across the membranes. Furthermore, we anchor low-surface-energy and photocatalytically active fluorinated titanium dioxide (F-TiO₂) nanoblocks at PLA fiber surfaces. This fluorinated modification introduces hydrophobicity and strong electronegativity, enabling self-decontamination and creating deep charge traps. More importantly, modulation of the electronic structure at the heterogeneous interfaces between ZIF-8 and F-TiO₂ induces directed electron migration and spatial charge redistribution. This establishes a continuous “capture‒storage‒regeneration” charge cycling mechanism. Consequently, the MRSD-PLA membranes demonstrate enhanced filtration efficiency against cross-scale pollutants such as particulate matter (PM) and pathogens, showing long-term stability even under high-humidity conditions. Collectively, this effort provides a theoretical foundation and a technical paradigm for developing hierarchically structured meta-membranes for environment-adaptive personal protection.

Results

Synthesis of MRSD-PLA meta-membranes

For medical surgical gowns and space suits, multifunctional protective membranes must simultaneously achieve high barrier performance, breathable comfort, and mechanical stability while incorporating additional properties to meet specialized environmental demands²³. To address these challenges, we employ a HHIS strategy to fabricate microenvironment-regulating and self-decontaminating meta-membranes (MRSD-PLA). These membranes are designed to overcome the performance degradation commonly exhibited by traditional materials under complex conditions by integrating multiple functionalities, including isolation protection, moisture-wicking permeability, self-cleaning, and signal acquisition. The core architecture of MRSD-PLA fiber consists of biodegradable PLA nanofibers serving as the structural scaffold. ZIF-8 nanocrystals with high porosity and electrochemical activity were embedded into individual PLA fibers via electrospinning. This creates ordered molecular transport channels that enable the directional diffusion of air and water vapor, thereby dynamically regulating the skin microenvironment (Fig. 1a). Moreover, the abundant coordinatively unsaturated sites in ZIF-8 serve as efficient electron traps for charge storage. Simultaneously, F-TiO₂ nanoblocks with low-surface energy and high electronegativity were anchored onto the fiber surface via electrospray, enabling hydrophobic self-cleaning and creating effective charge traps. When interfacial charges dissipate under external stimuli, the heterogeneous structure drives the directional migration of stored charges from ZIF-8 to the interface, which promptly replenishes the depleted surface charges²⁴. This establishes a closed-loop “capture-storage-regeneration” cycle that maintains stable electrostatic fields. Consequently, this HHIS approach significantly enhances the environmental adaptability and service reliability of the membranes, effectively suppressing performance degradation under extreme conditions.

Fig. 1. Synthetic routes and application scenarios of MRSD-PLA.

a Constructing heterogeneous interfaces within nanofibers via electrospinning-electrospray. b Microenvironment regulation and environmentally adaptive multifunctional integration for personal protection.

The MRSD-PLA membranes leverage their hierarchical interface structure to enable unidirectional transport of sweat vapor and metabolic heat outward, while their hydrophobically functionalized surface blocks liquid contaminants (Fig. 1b). These selectively designed mass and heat transfer channels ensure microenvironmental stability at the skin interface without compromising protection. Owing to the abundant charges stored in ZIF-8 nanocrystals and the deep charge traps created by F-TiO₂ nanoblocks²⁵, the membranes facilitate continuous electrostatic interception, effectively capturing pathogen-laden aerosols and submicron particles via strong electrostatic interactions. Even under high-humidity conditions, they maintain high surface potential along with stable dynamic charge retention and regeneration capabilities, thereby substantially mitigating the impact of environmental humidity fluctuations on protective efficacy.

We fabricated MRSD-PLA meta-membranes with hierarchically heterogeneous interface structures through internal structural regulation and surface functionalization of nanofibers. The inherent piezoelectric-triboelectric properties of the heterogeneous nanofibers enable real-time responses to mechanical motions, converting these stimuli into quantifiable electrical signals for continuous monitoring of the physiological status of the wearer²⁶. Furthermore, through the structural integration of nanocrystal-mediated charge storage, a mechanically stable PLA scaffold, and photocatalytically active hydrophobic nanoblocks, MRSD-PLA membranes achieve self-cleaning and antibacterial functionality while balancing mechanical strength during use and biodegradability after disposal. The meta-membranes not only overcome the inherent trade-off between protective efficacy and wearing comfort but also establish a design paradigm that advances personal protective materials toward intelligent, sustainable, and scenario-adaptive systems.

Fiber diameter distribution and pore architecture regulate the air permeability, moisture vapor transmission, and purification performance of the membrane²⁷. While composition dictates the physicochemical characteristics, crystal structure and heterogeneous interfaces primarily control mechanical stability and spatial charge redistribution. A clear elucidation of these structure-property relationships is therefore crucial for advancing the design of membranes that effectively regulate human microenvironments and enhance protection²⁸.

ZIF-8 nanocrystals were synthesized by coordinating Zn²⁺ with 2-methylimidazole ligands, forming a porous crystalline framework with well-defined channels (Fig. 2a). The short-chain linkers and precise coordination geometry afford a high surface area for gas adsorption and efficient molecular transport. Additionally, abundant coordinatively unsaturated Zn²⁺ sites act as electron traps for charge storage, establishing continuous conduction networks throughout the frameworks. Moreover, covalent grafting of fluorinated functional groups onto the TiO₂ surface significantly reduced its surface energy, enhancing hydrophobicity (Fig. 2b and Supplementary Fig. 1), whereas the high electronegativity of fluorine created deep-level charge traps. This fluorination treatment selectively modifies the surface chemistry without compromising the bulk crystallinity of TiO₂, allowing significant improvements in wetting behavior and surface electronic properties.

Fig. 2. Structural features of MRSD-PLA.

Synthetic routes and microstructure of a ZIF-8 nanocrystals and b F-TiO₂ nanoblocks. SEM images of c P-PLA, d MRSD-PLA2, e MRSD-PLA4, and f MRSD-PLA6. FTIR spectra of MRSD-PLA in the ranges of g 4000−650 cm⁻¹, h 1500−1300 cm⁻¹, i 1250−1150 cm⁻¹ and j 1160−1020 cm⁻¹. k XRD patterns of MRSD-PLA. l Nitrogen adsorption-desorption isotherms of ZIF-8 and MRSD-PLA. m, n Stress−strain curves and tensile strength of MRSD-PLA.

Scanning electron microscopy (SEM) images revealed the microscopic morphology of the components. ZIF-8 nanocrystals possessed a well-defined rhombic dodecahedral morphology and were closely packed through intercrystalline interactions, facilitating continuous gas transport channels. F-TiO₂ nanoblocks consisted of aggregated nanoparticles (30−50 nm), whose disordered stacking created micro/nanoscale pores and surface textures. Using an electrospinning-electrospray technique, we fabricated membranes with anchored F-TiO₂ at mass fractions of 0%, 2%, 4%, and 6%, with corresponding ZIF-8 mass fractions of 25%, 22.2%, and 20% (Fig. 2c–f). The incorporation of ZIF-8 increased the conductivity of the spinning solution, promoting polymer chain stretching and fiber refinement (Supplementary Figs. 2 and 3). Control experiments on the PLA@ZIF-8 membrane (without F-TiO₂) revealed that embedded ZIF-8 primarily enhanced charge storage and the water vapor transmission rate (WVTR). In contrast, the synergistic combination with surface-anchored F-TiO₂ nanoblocks was crucial for achieving superior hydrophobicity, the highest surface potential, and optimal filtration efficiency through the formation of hierarchical heterogeneous interfaces. Elemental mapping confirmed the uniform distribution of carbon (C), nitrogen (N), zinc (Zn), and fluorine (F) (Supplementary Fig. 4a). The mass fractions of F-TiO₂ in the composite membranes were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), with measured values in good agreement with nominal loadings, affirming the reliability of the electrospray process (Supplementary Fig. 4b, c).

The Fourier-transform infrared (FTIR) spectra in Fig. 2g–j reveal the characteristic functional groups of MRSD-PLA. P-PLA exhibited a C = O stretching vibration peak at 1750 cm⁻¹, along with characteristic C−O absorption peaks at 1180 cm⁻¹ and 1080 cm⁻¹. Following the incorporation of ZIF-8 and F-TiO₂, the MRSD-PLA spectra exhibited asymmetric stretching vibrations of aromatic and aliphatic C−H bonds from the imidazole ring at 3135 cm⁻¹ and 2928 cm⁻¹, respectively. The absorption peak at 1480 cm⁻¹ corresponded to C = N stretching in the imidazole ring, while the peak at 1383 cm⁻¹ was attributed to vibrations involving interfacial −CH₃ and O−O groups. The introduced nanoparticles perturb the electron cloud distribution in PLA chains, effectively reducing the force constants of relevant chemical bonds and consequently causing a red shift in the absorption peaks. The interfacial composition and bonding between ZIF‑8, F‑TiO₂, and PLA were further elucidated by X‑ray photoelectron spectroscopy (XPS) (Supplementary Fig. 4d–o). X-ray diffraction (XRD) analysis was employed to verify the successful incorporation of ZIF-8 within the PLA matrix and to elucidate its role as a nucleating agent modulating PLA crystallization (Fig. 2k). Specifically, P-PLA displayed a broad, weak diffraction peak, indicating low crystallinity typical of processed PLA. In contrast, the MRSD-PLA membranes exhibited sharp peaks at 7.3°, 10.5°, and 12.8°, respectively, assigned to the (011), (002), and (112) planes of ZIF-8 nanocrystals²⁹. Moreover, ZIF-8 acts as a nucleating agent to promote the crystallization of PLA, as indicated by the increased intensity of prominent peaks³⁰.

The nitrogen adsorption-desorption isotherms indicated that the specific surface areas of MRSD-PLA2, MRSD-PLA4, and MRSD-PLA6 were 168, 185, and 209 m²·g⁻¹ (Fig. 2l), which were significantly higher than that of the P-PLA membrane (18 m²·g⁻¹). This substantial increase arises from the synergistic effects of embedded ZIF-8 nanocrystals (providing intrinsic micropores) and anchored F-TiO₂ nanoblocks (creating nanoscale surface roughness). Together, they establish a multiscale porous network, where micropores mainly originate from ZIF-8, mesopores from inter-nanoblock spaces and fiber textures, and macropores from interfiber voids. This hierarchical porosity directly enhances gas adsorption capacity and facilitates efficient vapor/gas transport. The mechanical performance of MRSD-PLA under tensile loading is shown in Fig. 2m, n. Compared with P-PLA, MRSD-PLA demonstrated higher tensile strength and elastic modulus in both horizontal and vertical sampling orientations (Supplementary Fig. 5). Within the continuous PLA nanofiber matrix, ZIF-8 nanocrystals act as reinforcing agents to suppress crack propagation, while the F-TiO₂ nanoblocks enhance interfacial adhesion through heterogeneous structure formation³¹.

Microenvironment regulation

Heterogeneous composite fiber membranes with hierarchical roughness were fabricated by embedding ZIF-8 nanocrystals within PLA nanofibers and anchoring low-surface-energy F-TiO₂ nanoblocks at fiber surfaces. The resulting hydrophobic surface traps air in its grooves and pores, causing water droplets to contact mainly the trapped air and surface protrusions, thereby drastically reducing the solid–liquid contact area³². By leveraging the HHIS strategy, the water contact angle (WCA) of MRSD-PLA6 increased to 137.4° (Fig. 3a), substantially higher than that of P-PLA. MRSD-PLA membranes form interconnected microscale and nanoscale pores through random fiber stacking, enabling gas permeation via mass transfer driven by molecular thermal motion and concentration gradients (Fig. 3b). The micro-nano protrusions of low-surface-energy F-TiO₂ enhance hydrophobicity and suppress water spreading, which prevents clogging of fiber interstices and ZIF-8 micropores, ensuring efficient gas and vapor transport. Furthermore, these heterogeneous interfaces increase the specific surface area, offering abundant sites for adsorption and diffusion while promoting water evaporation at the fiber surfaces³³. This structure effectively inhibits moisture accumulation and heat retention at the interface, thereby improving overall moisture permeability. Water vapor permeability tests confirmed that the hierarchical pore structure of MRSD-PLA6 enables water vapor to undergo Fickian diffusion (concentration-gradient-driven), facilitating coupled transport of water vapor and heat³⁴. Owing to the concerted regulation of chemical composition and microstructure, condensed water droplets remain suspended on the surface for extended periods without penetration, demonstrating excellent water resistance and air permeability (Fig. 3c).

Fig. 3. Water vapor permeability and air breathability of MRSD-PLA.

a Water contact angle of MRSD-PLA. b Multiscale structural and functional evolution of MRSD-PLA. c Water vapor permeability test of MRSD-PLA6. d Time-resolved wetting dynamics and droplet detachment behavior of MRSD-PLA6. e Liquid repellency performance of MRSD-PLA6. f Self-cleaning process of MRSD-PLA6 under sand-water mixture contamination. g Comparison of WVTR between MRSD-PLA6 and commercial counterparts. h Schematic illustration of the waterproof and breathable mechanisms. i Air permeability of MRSD-PLA. j Schematic illustration of gas and vapor transport pathways in MRSD-PLA.

The MRSD-PLA6 maintained a high WCA over extended periods, demonstrating superior wetting resistance and stability against time-dependent degradation (Fig. 3d). Furthermore, its engineered hydrophobicity reduces liquid water retention on the membrane surface, facilitating easy removal with minimal residue. Hydrostatic pressure testing revealed that the MRSD-PLA6 resisted 116 mm H₂O, significantly higher than the 84 mm H₂O for the P-PLA. Wicking tests indicated a wicking height of 36 mm for P-PLA, while MRSD-PLA6 reached 20 mm (Supplementary Fig. 6). These anti-wetting characteristics collectively enable MRSD-PLA to consistently repel various liquids (including water and bodily fluids), providing a reliable barrier for personal protective equipment (Fig. 3e). The self-cleaning mechanism arises because the adhesion force between particles and the hydrophobic surface is weaker than the cohesive force within water droplets (Fig. 3f). Consequently, rolling water droplets can carry away surface contaminants. This process is governed by the interplay of tuned wettability and heterogeneous interfaces, which promotes rapid contaminant detachment from the fiber surfaces².

The macroscopic properties of nanofiber membranes, including air permeability, moisture vapor transmission, and mechanical performance, directly influence the comfort, durability, and application scope of textile-integrated products. The MRSD-PLA6 exhibited a WVTR of 4018 g·m⁻²·d⁻¹ (measured at 25 °C, 90% RH), significantly surpassing that of most commercial protective materials (Fig. 3g). This value exceeds the established threshold of 2000 g·m⁻²·d⁻¹ specified in derived from protective clothing standards, ensuring adequate moisture dissipation during perspiration. The incorporation of ZIF-8 and F-TiO₂ does not increase resistance to water vapor transmission but instead facilitates the development of heterogeneous structured fibers with optimized pore morphology, thereby enhancing vapor diffusion efficiency (Fig. 3h). Air permeability, a key indicator for evaluating energy exchange and cellular metabolic environments, is critical for reducing the risks of skin inflammation and thermal stress³⁵. Consistent with this requirement, MRSD-PLA membranes demonstrated efficient gas transport owing to their high specific surface area, high porosity, and interconnected networks, achieving air permeability values above 60 mm·s⁻¹. In contrast, P-PLA exhibited an air permeability of only 46.8 mm·s⁻¹ due to its dense structure and limited porosity (Fig. 3i). The highly porous structure of ZIF-8 and the resulting heterogeneous interfaces provide abundant nanoscale transport pathways for gases and vapor, including diffusion along fiber surfaces and heterogeneous boundaries, through intrinsic ZIF-8 channels, and through interparticle spaces among F-TiO₂ nanoblocks (Fig. 3j and Supplementary Fig. 7).

Passive signal acquisition

The surface potential of MRSD-PLA6 reached 5.8 kV, representing a 75.7% increase over P-PLA (Fig. 4a). Crucially, the low-surface energy and hierarchically rough structure of MRSD-PLA6 effectively suppress carrier migration and markedly mitigate environmental charge dissipation³⁶, enabling the membrane to maintain high potential stability for over 90 days. In contrast, P-PLA exhibited significant charge decay due to water infiltration-induced ion conduction and dipole relaxation. The surface-enriched, highly electronegative fluorine-containing groups attract and localize interfacial carriers. This restricts their migration, leading to the formation of a stable polarized interface that enhances the interfacial dielectric properties. Consequently, MRSD-PLA membranes achieve a high relative dielectric constant and energy storage density while maintaining low dielectric loss. At 10³Hz, the relative dielectric constant of MRSD-PLA6 reached 1.72, which is 1.24 times that of P-PLA (Fig. 4b). The occasional deviations of data points from the fitting curve are attributed to the inherent heterogeneity in charge trap distribution and interfacial polarization across the hierarchical composite fibers (Fig. 4c). Electrostatic adsorption experiments further demonstrated that the enhanced electrostatic interactions overcame the kinetic barriers of particles in airflow, enabling MRSD-PLA6 to efficient capture fine particles (inset of Fig. 4c).

Fig. 4. Mechanisms of directed electron migration and charge redistribution in MRSD-PLA.

a Surface potential decay of MRSD-PLA after 90 days, 24 h of high humidity, and humidity cycling. b Relative dielectric constants of MRSD-PLA. c Correlation between surface potential and relative dielectric constants of MRSD-PLA. The inset shows the electrostatic adsorption assessment of MRSD-PLA6. d Surface electrostatic potential distribution of PLA molecular chains before and after polarization. e Schematic illustration of spatial charge modulation in nanofibers via HHIS Strategy. f Simulated potential distribution during the contact-separation cycle. g Schematic of electron trajectories across heterogeneous interfaces. Electrical output performance of MRSD-PLA, including h open-circuit voltage, i short-circuit current and j transferred charge. k Open-circuit voltage of MRSD-PLA6 under different humidity gradients. l Output stability of open-circuit voltage in MRSD-PLA6 over 500 s cycling. l₁–l₄ Open-circuit voltage fluctuations at different time intervals during cycling.

During high-voltage electrospinning, the external electric field aligns PLA molecular dipoles, enhancing the overall dipole moment (Fig. 4d). The embedded electroactive ZIF-8 nanocrystals adsorb and stabilize free charges through coordination polarization and π-electron delocalization, suppressing charge dissipation. Simultaneously, the high electronegativity of F-TiO₂ nanoblocks confines surface charges via interfacial dipole-dipole interactions. Owing to energy band differences, charge traps form at the two heterogeneous interfaces (ZIF‑8/PLA and F‑TiO₂/PLA)³⁷. These traps capture triboelectrically or polarization-generated free charges, significantly extending charge lifetime and enhancing surface electrostatic accumulation (Fig. 4e). The combined stabilization of internal charges, external charge confinement, and cooperative dipole alignment thus enhances the surface activity of MRSD-PLA, yielding superior electrostatic performance for applications like air purification.

The heterogeneous structured fibers in MRSD-PLA establish localized charge-transfer channels that significantly enhance the conversion efficiency of mechanical to electrical energy by facilitating interfacial charge separation and migration. COMSOL simulations reveal that during contact-separation cycles, enhanced surface polarization and charge storage lead to the accumulation of opposite charges at the interfaces^19,38. The subsequent release of these separated charges generates a substantial electrical output (Fig. 4f). The surface roughness from F-TiO₂ increases the contact area for friction, and its substantial electronegativity difference enhances charge separation. Whereas, the electroactivity of ZIF-8 facilitates charge transfer through polarization effects, increasing the charge yield per triboelectric event. Furthermore, favorable energy band alignment at the heterogeneous interfaces reduces the energy barrier for interfacial charge transfer, accelerating the directional transmission of triboelectric signals (Fig. 4g).

The triboelectric output was measured in a contact-separation mode between the meta-membranes and an external counter electrode (Supplementary Fig. 8). The electrical output performance of MRSD-PLA with different F-TiO₂ loadings is shown in Fig. 4h–j. Specifically, MRSD-PLA6 exhibited an open-circuit voltage of 22.3 V, a short-circuit current of 67.5 nA, and a transferred charge of 8.2 nC, representing improvements of 248%, 224%, and 925% over P-PLA. Charges predominantly accumulate at the interfaces between the nanomaterials and PLA fibers, which act as efficient sites for charge separation³⁹. The well-matched energy levels of ZIF-8 and F-TiO₂ generate interfacial electric fields that promote the separation of triboelectric charges and suppress electron recombination. Consequently, the complementary functions of F-TiO₂ in charge separation and ZIF-8 in charge storage/transfer synergistically enhance the triboelectric output⁴⁰. Even under high humidity, the micro-nano rough structures trap air to form a barrier that prevents direct contact between water molecules and charge storage sites, thereby maintaining stable charge transfer during contact electrification. MRSD-PLA6 exhibited only 10.3% voltage attenuation under gradient humidity conditions (Fig. 4k), effectively mitigating the charge neutralization and performance degradation common in P-PLA. The spatial charge redistribution induced by heterogeneous interfaces drives directional electron migration, which enables continuous conversion of mechanical to electrical energy over repeated cycles⁴¹. MRSD-PLA6 maintained a stable voltage output over 500 seconds of continuous operation (Fig. 4l), highlighting its substantial promise for applications in long-term energy storage, signal transmission, and real-time physiological monitoring.

Air purification

Efficient filtration of aerosols, droplet nuclei, and pathogen-laden particles (0.3–5 μm) is critical for constructing high-performance bidirectional protective systems⁴². Capitalizing on the excellent surface electroactivity, water resistance, and air permeability of MRSD-PLA membranes, we systematically evaluated their air purification performance under various operating conditions. MRSD-PLA with heterogeneous interface structures exhibited high filtration efficiency for the most penetrating PM_0.3 across varying flow rates (Fig. 5a, b). Notably, at 10 L·min⁻¹, MRSD-PLA maintained a PM_0.3 filtration efficiency exceeding 99.1% with a pressure drop of only 51.9 Pa, demonstrating high purification efficiency and low energy consumption. At 85 L·min⁻¹, P-PLA showed a significant decrease in filtration efficiency to 71.3%, accompanied by a pressure drop exceeding 400 Pa, while MRSD-PLA exhibited only a slight decrease in efficiency and a limited increase in flow resistance (Supplementary Figs. 9 and 10).

Fig. 5. Air filtration performance and mechanisms of MRSD-PLA.

Plots of a PM_0.3 filtration efficiency, b pressure drop, and c quality factor of MRSD-PLA at varying airflow capacity. PM_2.5 filtration efficiency of MRSD-PLA6 d before and e after water washing. f Long-term stability of PM_2.5 filtration efficiency for MRSD-PLA6 after water washing. The inset shows SEM image after filtration. g PM_2.5 filtration efficiency under 90% RH for 24 h. h PM_2.5 filtration efficiency under humidity cycling conditions i pore size distribution and j porosity of MRSD-PLA. k Schematic illustration of electrostatic interactions and the functional mechanism in MRSD-PLA. l Schematic illustration of dynamic charge balance induced by heterogeneous interface structuring.

As the flow rate increases, the two membranes exhibit markedly distinct performance trends. This divergence is fundamentally due to the synergistic enhancement of structural stability, charge retention, and mass transfer efficiency in MRSD-PLA, achieved by embedding ZIF-8 and anchoring F-TiO₂. For P-PLA, elevated flow rates generate an aerodynamic drag force on PM that exceeds its limited electrostatic adsorption capacity, leading to submicron particle penetration⁴³. Concurrently, its relatively weak fiber network undergoes compaction under high-velocity airflow, reducing effective porosity and resulting in pore constriction, thereby significantly increasing air resistance. In contrast, the ZIF-8 nanocrystals embedded within the fibers introduce abundant nanopores and a high specific surface area. These features enhance physical interception mechanisms, including size exclusion and surface adsorption, while providing stable charge storage sites that maintain superior electrostatic capture (Supplementary Fig. 11). The surface-anchored F-TiO₂ nanoblocks leverage their high electronegativity and crystalline-amorphous interfaces to form deep charge traps on the fiber surfaces. These traps sustain a robust electrostatic field through continuous charge collection and storage, which enables effective PM capture. Furthermore, the multiscale structural modulation of both the fiber interior and surface significantly enhances mechanical strength. This enables the membranes to resist deformation under high flow rates, maintain an interconnected porous structure, and suppress pressure drop increase. This structural superiority was further confirmed by higher quality factor (QF) values (Fig. 5c). Notably, MRSD-PLA6 demonstrates a superior balance of high filtration efficiency and low pressure drop compared to conventional high-efficiency filtration media such as N95 melt-blown layers and fiberglass filters (Supplementary Table 1).

We fabricated nanofiber membranes with heterogeneous interface structures via the HHIS strategy, modulating their surface wettability to systematically investigate how water washing affects PM filtration efficiency. Before washing, MRSD-PLA6 maintained a 95% filtration efficiency for PM_2.5 at 85 L·min⁻¹ through combined physical interception (e.g., inertial impaction, Brownian diffusion) and electrostatic adsorption (deep charge traps, heterogeneous interfaces), whereas P-PLA, lacking such design, exhibited only 88.2% efficiency (Fig. 5d). After 30 minutes of water immersion and drying, MRSD-PLA6 retained a PM_2.5 filtration efficiency of 89.1% (from 98.6%), whereas the efficiency dropped sharply to 65.4% of P-PLA (Fig. 5e). Furthermore, the F-TiO₂ nanoblocks remained stably anchored owing to strong interfacial adhesion, demonstrating excellent structural robustness, environmental tolerance, and reusability without observable detachment, as confirmed by SEM after repeated washing cycles (Supplementary Fig. 12a, b). Negligible F-TiO₂ mass loss was confirmed by inductively coupled plasma-mass spectrometry (ICP-MS) via quantifying Ti release during successive washes (Supplementary Fig. 12c). More importantly, owing to stable charge storage and structural recovery mechanisms, MRSD-PLA6 maintained stable PM_2.5 filtration over extended periods (Fig. 5f). The performance stability can be explained by three mechanisms: (1) Strong hydrophobic groups reconfigure the hydration structure at the solid‑liquid interface, inhibiting charge dissipation from water ionization and enhancing interfacial charge retention; (2) Under external disturbances, the heterojunction electric field drives stored charges from ZIF‑8 to the interface, promptly compensating for transient surface loss and establishing a closed‑loop “capture‑storage‑regeneration” cycle that sustains the electrostatic field^7,44; (3) The Martindale abrasion test indicates that the F-TiO₂ nanoblocks exhibit excellent adhesion stability under frictional conditions, which ensures the safety and long-term functionality of the membrane material (Supplementary Figs. 13 and 14).

After 24-h exposure to 90% RH and multiple humidity cycles, MRSD-PLA6 retained a PM_2.5 filtration efficiency above 85.3% while maintaining a pressure drop below 78.3 Pa (Fig. 5g, h and Supplementary Fig. 14). Notably, the fluorinated interface suppresses water-mediated charge shielding through three synergistic effects: forming a hydrophobic barrier to reduce direct water contact, modulating the interfacial hydration structure to inhibit ion conduction, and synergizing with heterogeneous charge traps to enhance charge confinement. Collectively, these effects ensure stable surface potential and filtration performance under high humidity. The exceptional water vapor permeability of MRSD-PLA membranes arises from Knudsen and surface diffusion mechanisms within their hierarchical pore network. The pore size distribution indicated a substantial fraction of mesopores (Fig. 5i). Given that the mean free path of water vapor (~110 nm) exceeds these pore diameters, mass transfer is significantly enhanced by Knudsen diffusion, a regime dominated by molecule-wall collisions. Concurrently, the high specific surface area, predominantly from microporous ZIF-8, facilitates the adsorption and subsequent surface diffusion of water molecules (Fig. 5j).

Under challenging conditions, ZIF-8 nanocrystals within the heterogeneous fibers stabilize free charges through their electroactivity, while F-TiO₂ nanoblocks leverage their strong electronegativity to confine surface charges via interfacial dipole effects. The heterogeneous interfaces create charge traps through band alignment differences. Together, these mechanisms establish a persistent electrostatic field that actively captures submicron and nanoparticles. Meanwhile, the microporous structure of ZIF-8 forms nanoscale capture channels within the fibers, and F-TiO₂ nanoblocks create micro-nano rough structures on the surfaces. These constitute a multilevel physical capture network that integrates interception, inertial impaction, and diffusion, enabling efficient filtration across particle sizes. As discrete embeddings within PLA fibers, ZIF-8 nanocrystals avoid clogging internal micropores and interfiber macropores while maintaining continuous airflow pathways, thereby reducing bypass losses. The low-surface energy of F-TiO₂ nanoblocks inhibits pore adhesion from water adsorption, while their surface micro-nano structure induces an air slip effect that reduces viscous resistance at the airflow-fiber interface⁴⁵. This synergy enables MRSD-PLA to achieve filtration performance and stability superior to systems relying on either mechanism alone (Fig. 5k, l).

Self-decontamination and biodegradability

The warm, humid microenvironment formed on the skin surface during prolonged activity facilitates bacterial proliferation⁴⁶. Microorganisms thrive on metabolizing in sweat, rapidly proliferating, disrupting the physiological barrier of the skin, and potentially inducing inflammation or infection. This underscores the critical demand for materials that can simultaneously regulate the microenvironment and actively decontaminate. The antibacterial properties of MRSD-PLA against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were evaluated using the plate counting method (Fig. 6a). P-PLA itself showed a modest reduction in bacterial viability, likely due to its inherent low-surface energy. MRSD-PLA demonstrated high inactivation efficiency against both strains, and their antibacterial performance improved notably with increasing F-TiO₂ nanoblocks content. Specifically, MRSD-PLA6 achieved a bacterial inhibition rate of 90.3%, significantly higher than that of P-PLA (Fig. 6b).

Fig. 6. Antibacterial mechanisms and compost degradation behavior of MRSD-PLA.

a Antibacterial performance of MRSD-PLA. Blank represents the control group. b Antibacterial efficiency of MRSD-PLA. c Schematic illustration of the multi-mechanism antibacterial activity of MRSD-PLA. d Molecular-level antibacterial mechanism of MRSD-PLA. e MRSD-PLA toxicity test on L929 cells. f Dead/live staining results of L929 cells after co-culture with P-PLA, MRSD-PLA6, and the control group for a certain period of time. g Compost degradation behavior of MRSD-PLA6 after soil burial.

Through micro-nano structural characterization and molecular-level analysis, the multi-mechanism antibacterial activity of MRSD-PLA with heterogeneous interfaces was further elucidated (Fig. 6c). The Zn²⁺ coordination sites in ZIF-8 and surface hydroxyl groups on F-TiO₂ act synergistically to enhance reactions between photogenerated charge carriers and adsorbed O₂/H₂O molecules on the material surface⁴⁷. This generates highly oxidative free radicals, primarily reactive oxygen species (ROS). The ROS penetrate bacterial cell membranes, degrade nucleic acids and proteins, disrupt cellular integrity, and ultimately cause metabolic dysfunction leading to bacterial death. Furthermore, the strong electrostatic attraction at the heterogeneous interface firmly adsorbs bacteria onto the fiber surfaces, prolonging their exposure to ROS and thereby enhancing bactericidal efficacy⁴⁸. Moreover, electrostatic interactions can disrupt the electrochemical potential balance across bacterial membranes, inhibit active nutrient transport and key enzymatic activities, thereby effectively hindering bacterial proliferation (Fig. 6d)⁴⁹. Antibacterial tests under dark conditions and with ROS scavengers confirmed that ROS and electrostatic adsorption act synergistically to enhance the antimicrobial performance (Supplementary Fig. 15a). Adequate biosafety was demonstrated by low Zn2+ release levels and favorable cytotoxicity profiles (Fig. 6e, f and Supplementary Fig. 15b), in line with previously reported PLA membranes⁵⁰.

Biodegradable materials can be progressively broken down by microorganisms in natural environments such as soil and compost, ultimately mineralizing into carbon dioxide and water (Supplementary Fig. 16). To assess the degradation behavior of membranes with heterogeneous interfaces, P-PLA and MRSD-PLA6 were subjected to burial experiments in moist soil at 40 °C, simulating warm, humid natural conditions to accelerate polymer chain scission through enhanced microbial metabolism and enzymatic activity^14,51. After 84 days, both membranes underwent significant degradation and lost structural integrity (Fig. 6g), directly demonstrating their biodegradability and the potential of the HHIS strategy to regulate the environmental lifecycle of such materials. SEM images revealed abundant colonization by microorganisms capable of secreting PLA-degrading enzymes on the membrane surfaces (Supplementary Fig. 17). These enzymes mediate hydrolysis that cleaves the PLA chains into small, environmentally benign molecules⁵².

In vitro biodegradation kinetics showed that the membranes exhibited significant fiber fracture and embrittlement within 14 days, followed by extensive structural disintegration by day 28, and further fragmentation into millimeter-sized fragments between days 42 and 56 (Supplementary Fig. 18). Quantitative analysis confirmed their biodegradability, with mass loss exceeding 75% over 84 days. Although interfacial modifications in MRSD-PLA6 partially suppressed initial microbial attachment, the inherent biodegradability of PLA ultimately dominated the degradation process under prolonged environmental exposure. This demonstrates that the HHIS strategy enables dual regulation of material performance and degradability. During service, the heterogeneous interfaces formed by ZIF-8 and F-TiO₂ synergistically maintain mechanical integrity and functional stability^53,54. After disposal, the material undergoes orderly degradation via microbial enzymatic hydrolysis, achieving functional integration from efficient protection to minimal environmental impact^55,56. Thus, the HHIS strategy establishes a sustainable paradigm for designing high-performance yet biodegradable disposable protective equipment.

Discussion

In summary, meta-membranes with combined adaptive microenvironment regulation and self-decontamination are realized through a strategy of hierarchically structured heterogeneous interfaces. The embedding of highly electroactive, porous ZIF-8 nanocrystals within the fibers creates efficient molecular transport pathways. MRSD-PLA membranes exhibit high moisture permeability (4018 g·m⁻²·d⁻¹) and air breathability (> 60 mm·s⁻¹), facilitating rapid sweat and heat dissipation for real-time microenvironment regulation. The synergy between internal embedding and surface modification constructs heterogeneous fiber interfaces. This architecture generates micro-nano roughness and deep charge traps, promoting directional electron transfer and spatial charge redistribution. Thus, performance degradation under fluctuating environments is effectively mitigated. Even under high-humidity, MRSD-PLA membranes maintain a stable surface potential, reliable electrical signal transmission, and high PM filtration efficiency. The hierarchical structures synergistically inhibit bacterial proliferation through multiple mechanisms while balancing in-use mechanical strength with post-disposal biodegradability. This work establishes a generalizable paradigm for the rational design of next-generation, high-performance personal protective membranes.

Methods

Materials

Poly(lactic acid) (PLA) with a molecular weight of 1.63 × 10⁵g·mol⁻¹ was procured from Total Corbion PLA Co., Ltd., Thailand. Non-woven cellulose fabrics (60 g·m⁻²) were bought by Sateri Fiber Co., Ltd., China. N,N-dimethylformamide (DMF, >98.0%) and dichloromethane (DCM, >98.0%) were supplied by Sinopharm Chemical Reagent Co., Ltd. (China). Zinc acetate dihydrate (C₄H₁₀O₆Zn, >98.0%), 2-methylimidazole ( > 98.0%), titanium(IV) isopropoxide (TTIP, >97.0%), isopropyl alcohol (IPA, ≥ 99.5%), ethanol (EtOH, ≥99.8%), and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES, 97.0%) were obtained from Macklin Biochemical Co., Ltd.

Synthesis of ZIF-8 nanocrystals

ZIF-8 nanocrystals were synthesized via a microwave-assisted method. Briefly, zinc acetate dihydrate (0.55 g) and 2-methylimidazole (4.1 g) were separately dissolved in deionized water (60 mL). The combined solution was reacted in a microwave reactor at 140 °C for 10 min. The resulting solid product was collected by centrifugation, vacuum-dried at 80 °C for 12 h, and obtained as highly electroactive and porous ZIF-8 nanocrystals.

Synthesis of F-TiO2 nanoblocks

Fluorinated TiO₂ (F-TiO₂) nanoblocks were prepared as follows. First, TiO₂ was synthesized by hydrolyzing a mixture of titanium(IV) isopropoxide (TTIP, 10 mL) and isopropyl alcohol (IPA, 40 mL) in a 1:1 (v/v) water/IPA solution under stirring. The mixture was reacted in a microwave reactor at 180 °C for 1 h. The resulting precipitate was collected by centrifugation, vacuum-dried at 80 °C for 6 h, and then calcined at 500 °C for 1 h to obtain anatase-phase TiO₂. Subsequently, the TiO₂ (2.0 g) was dispersed in a solution of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES, 5.0 g) in ethanol (45.0 g) for surface fluorination, affording F-TiO₂ nanoblocks with low-surface energy and high electronegativity.

Preparation of P-PLA nanofiber membranes

PLA granules (1.0 g) were dissolved in a mixed solvent of DMF and DCM (3:7, v/v) with continuous stirring for 12 h to form a homogeneous electrospinning solution. Electrospinning was conducted at an applied voltage of 30 kV and a feed rate of 1.0 mL·min⁻¹ for 1.5 h under ambient conditions (25 °C, 35 ± 5% RH). The resulting nanofiber membranes were vacuum-dried at 40 °C for 12 h to obtain the pristine PLA membrane, denoted as P-PLA.

Preparation of MRSD-PLA meta-membranes

The composite meta-membranes (MRSD-PLA) were fabricated via a combined electrospinning-electrospray process. First, a spinning solution was prepared by dissolving PLA (1.0 g) and dispersing ZIF-8 nanocrystals (0.4 g) in a DMF/DCM mixed solvent (3:7, v/v) under stirring. Separately, hydrophobic F-TiO₂ nanoblocks (0.2, 0.4, or 0.6 g) were ultrasonically dispersed in ethanol (10 mL) to form stable suspensions. The spinning solution was electrospun at 30 kV with a feed rate of 1.0 mL·min⁻¹. Simultaneously, the F-TiO₂ suspensions were electrosprayed onto the forming fibers at 30 kV with a feed rate of 1.0 mL·min⁻¹ for 15 min. The entire process was conducted under ambient conditions (25 °C, 35 ± 5% RH). After vacuum drying, the resulting membranes were designated as MRSD-PLA2, MRSD-PLA4, and MRSD-PLA6, corresponding to the increasing mass of F-TiO₂ used.

Moisture permeability and air breathability tests

Gas permeation properties were evaluated using a differential pressure method. A membrane sample with an effective area of 20 cm² was sealed between two chambers⁵⁶. The upstream chamber was filled with high-purity test gases at a constant pressure of 100 kPa, while the downstream chamber was evacuated and maintained under dynamic vacuum. The steady-state gas flux was quantified with a soap-film flowmeter, and permeability was calculated based on Fick’s law of diffusion. The WVTR was determined using the standard gravimetric cup method under controlled conditions (25 °C, 90 ± 2% RH). with a performance threshold of >2000 g·m⁻²·d⁻¹ referenced from industry standards (ISO 15496 and ASTM F1868). The membrane was securely sealed over a cup containing a desiccant (anhydrous calcium chloride) to create a constant humidity gradient. The mass change was periodically measured using a high-precision electronic balance. The WVTR was calculated from the steady-state mass change per unit time and normalized to the membrane area. For comparative analysis, the following commercial materials were tested: an activated carbon mask (Bao Weikang Co., China), a PurCotton® Everyday Non-medical Mask (Winner Medical Co., China), and a PurCotton® Cotton Facial Mask (Winner Medical Co., China).

Air purification performance evaluation

The filtration performance against PM was evaluated using a homemade testing system⁵⁵. The airflow rate was controlled at 10, 32, 65, and 85 L·min⁻¹ using a high-precision pump, corresponding to face velocities of 2.2, 6.9, 14.1, and 18.0 cm·s⁻¹ (Supplementary Table 2). Sodium chloride (NaCl) aerosol particles generated by a nebulizer served as the challenge aerosol. Filtration efficiency was measured simultaneously upstream and downstream using two laser particle counters, while the pressure drop across the membrane was monitored in real-time with differential pressure sensors. To evaluate washing durability, the membranes were immersed in deionized water to remove accumulated PM, dried via a standard protocol, and then re-tested. For high-humidity tests, the environmental humidity was controlled by the saturated salt solution method and monitored continuously with a digital sensor. All measurements were performed in triplicate at different locations on each sample to ensure representativeness, and results are reported as mean ± standard deviation.

Degradation behavior analysis

The biodegradation of membrane specimens was evaluated using a natural soil burial method. Samples (5 × 5 cm²) were buried at a depth of 5 cm in pots containing a standard test soil and placed in an outdoor environment to undergo natural weathering (e.g., solar radiation, precipitation). To sustain microbial activity, fresh soil was supplemented weekly. Degradation progression was monitored by regularly examining the surface morphology via optical microscopy, noting visual changes such as cracking, discoloration, or fragmentation.

Reporting summary

Further information on research design is available in the Nature Portfolio Reporting Summary linked to this article.

Author contributions

H.X. and X.J.H. conceived the idea and designed the experiments. S.-Z.W. and G.Y.Z. performed the experiments. X.-H.W., J.-L.G., Z.H., and Y.Z. contributed to materials characterizations. X.-P.L. and G.J.F. joined the discussion of the data and gave helpful suggestions. S.-Z.W. and H.X. wrote the manuscript. All authors participated in drafting the paper and gave approval to the final version of the manuscript.

Peer review

Peer review information

Nature Communications thanks Guo-Hong Tao, and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. A peer review file is available.

Data availability

The data supporting the findings of this study are included within the Article and its Supplementary Information. Source data are provided with this paper. Source Data file has been deposited in Figshare under accession code 10.6084/m9.figshare.30639503. Source data are provided with this paper.

Competing interests

The authors declare no competing interests.

Supplementary information

The online version contains supplementary material available at 10.1038/s41467-026-72873-z.