Low-voltage driven anticounterfeiting textile display based on alternating current electroluminescent fibers

Abstract

Wearable textile displays have attracted increasing attention for next-generation information interaction because of their inherent flexibility and skin conformity. However, conventional wearable textile display devices usually require high driving voltages, which pose serious safety risks and greatly limit its practical application in wearable scenarios. Therefore, it is urgent to develop low-voltage-driven textile devices for wearable applications. In this work, a low-voltage driving strategy is developed by introducing a highly transparent high-dielectric solution into the emissive layer and compounding with BaTiO₃. In addition, a low-voltage-driven dynamic textile anti-counterfeiting device was fabricated using multicolor luminescent fibers. The fabricated multicolor fiber exhibits excellent flexibility, with negligible luminance attenuation after 10,000 bending cycles. In addition, it can be successfully lit up at a driving voltage of 45 V, and a luminance of 90 cd·m⁻² can be achieved at a driving electric field of 4 V/μm, demonstrating favorable optoelectronic performance and reliable anti-counterfeiting capability. Under dual-mode excitation by an electric field and ultraviolet light, the device can achieve reversible switching between blue and orange light emission, thus exhibiting both low-voltage driving characteristics and excellent anti-counterfeiting performance. These results indicate that the developed multicolor alternating-current electroluminescent fiber has promising application potential in wearable anti-counterfeiting textile devices.

Wearable textile displays have emerged as a promising platform for next-generation information interaction due to their inherent flexibility and skin conformity, but conventional devices typically require high driving voltages, which introduce safety risks and hinder their applicability. Here, the authors produce a low-voltage-driven anti-counterfeiting device using multicolor luminescent fibers, demonstrating negligible luminance attenuation after 10,000 bending cycles, a luminance of 90 cd·m⁻² at a driving electric field of 4 V/μm and reversible colour switching.

Introduction

Textile displays are an innovative outcome of the deep integration of flexible electronics and textile technology^1–4. As core components of next-generation smart wearable systems, textile displays not only enable intuitive visual interaction and information presentation in everyday textiles, but also promote the transformation of the textile industry toward intelligence and multifunctionality. To meet the stringent requirements for flexibility and conformability in wearable scenarios, display architectures have undergone continuous evolution, progressing from rigid bulk materials to flexible films and further to fiber-shaped devices^5–8. Owing to their unique compatibility with textile structures and excellent mechanical adaptability, fiber-based wearable displays have shown broad application prospects in consumer electronics, healthcare, and information security. The applications for fiber light sources have been expanding in photomedicine and optical sensors^9–12. Li et al. developed a multifunctional fiber-optic theranostic probe for closed-loop tumor photothermal therapy by co-immobilizing absorption spectrally separate agents, exhibiting the excellent therapeutic efficacy and biocompatibility of the probe⁹. In addition, fiber optic sensors have attracted considerable attention for their unique intrinsic advantages, including lightweight, long sensing length, remote detection, high sensitivity, high selectivity, immunity to electromagnetic interference, and so on^11,12.

At present, textile display devices are mainly developed based on display technologies such as organic light-emitting diodes (OLEDs), quantum dots (QDs), alternating-current electroluminescence (ACEL), and electrophoretic displays (EPDs)^13–16. The fiber-based LED, OLED, QLED, and PLEC devices rely on complex fabrication routes such as thermal evaporation, photolithography, and welding, which are limited to small-scale preparation, as shown in Table S1. For textile-based OLEDs, Choi et al. fabricated a textile display with luminance of 12,748 cd/m² and current efficiency of 23.8 cd/A¹⁷. Furthermore, Lee et al. deposited the passivated phosphorescent OLED fibers on rectangular ITO/PET substrates to realize matrix-addressable textiles with high luminance (∼4300 cd/m² at 5 V)¹⁸. For textile QLED displays, Lee et al. realized waterproof woven fiber QLEDs with peak luminance of 463 cd/m², 482 cd/m², and 188 cd/m² for red, green, and blue light¹⁹. Then, Yang et al. achieved high-luminance (6325 cd/m²) addressable devices stable over 500 bends based on ultrathin metal MoO₃/Au electrodes, while interfacial delamination degrades long-term stability²⁰. For textile-based perovskite fiber LEDs, Ren et al. prepared stretchable, woven full-color fiber-PLEDs via the dip-coating method²¹. The perovskite fiber LEDs exhibited narrow EL peaks, decent red/green/blue multicolor luminance, PDMS-enabled waterproof capability, high EQE of 15.2%, and sustained stable light emission under 100% tensile strain. However, the above technologies suffer from the challenges including insufficient flexibility, complicated fabrication methods, and limited area and size for mass production. Compared with these technologies, ACEL has become one of the most competitive candidates in the field of textile displays because of its simple structure, excellent flexibility, and suitability for large-area fabrication²². Moreover, the ACEL textile display possesses superior softness, mechanical compliance, air permeability, and moisture permeability, which are critical properties for long-term wearable applications. The ACEL fiber-based display overcomes the poor wearability and durability limitations of traditional fiber light-emitting devices, demonstrating prominent application prospects in wearable textile electronics²³. The ACEL emissive layer can be uniformly coated onto the surface of fiber electrodes through a dip-coating process, and large-area pixelated luminous textiles can be successfully constructed by weaving ACEL luminescent fibers with transparent conductive fibers²⁴. In addition, through structural design or the incorporation of color-conversion materials, researchers have realized multicolor and even full-color textile displays, further expanding the application scenarios of ACEL textile display devices^25–27. However, as an important development direction of flexible displays, wearable ACEL textile displays still face two core challenges, namely operational safety and luminescent performance, among which operational safety, especially the safety risks associated with the driving voltage, has become a key bottleneck restricting their large-scale commercial application²⁸. A high driving voltage not only increases device energy consumption, but may also lead to potential safety hazards such as skin irritation and electric shock, thereby seriously reducing the practicality of wearable textile display devices^28–30.

Currently, waterborne polyurethane (WPU) is a widely used matrix material in wearable textile displays^31–33. However, its low dielectric constant results in insufficient electroluminescent brightness and a relatively high driving voltage³⁴, which not only compromises display performance but also introduces safety risks, making WPU-based devices difficult to satisfy the stringent safety requirements for wearable applications. In recent years, extensive efforts have been devoted worldwide to low-voltage driving technologies for ACEL devices, and significant progress has been achieved through the design of high-dielectric-constant materials, the development of novel electrodes, and the optimization of printing or spraying processes. For example, Li et al. introduced propylene carbonate (PC), a small molecule with a high dielectric constant, into the polyurethane acrylate/4-acryloylmorpholine (PUA/ACMO) polymer matrix, thereby preparing uniform and transparent inks. By combining screen printing with a one-step photopolymerization process, the driving electric field was reduced to 0.33 V/μm, and a luminance of 100 cd/m² was achieved at 1 V/μm. The underlying mechanism is that the homogeneous high-dielectric system can uniformly enhance the electric field and reduce light scattering, thereby allowing a greater proportion of the effective voltage to act on the phosphors³⁵. Hu et al. fabricated textile-based ACEL devices with a BaTiO₃/PVDF-HFP high-dielectric dielectric layer using an all-spray process, which significantly reduced the driving voltage. The resulting device achieved a luminance of up to 338.6 cd/m² at 188 V. This improvement is attributed to the precise control of film thickness by the spray process, the enhanced electric-field concentration effect, the intimate interfacial contact that reduces interfacial loss, and the uniform dispersion of functional particles that avoids electric-field distortion³⁶. Chen’s group replaced indium tin oxide (ITO) with chemical-vapor-deposited graphene as a flexible transparent electrode to construct ACEL devices, achieving a low turn-on voltage of 80 V and a luminance of 1140 cd/m² at 480 V. These advantages mainly arise from the low sheet resistance, high optical transmittance, and excellent flexibility of graphene, which effectively reduce the electrode voltage drop and improve emission uniformity³⁷. Although the above approaches are effective in reducing the driving voltage, they are all mainly applicable to planar devices, and there is still no mature strategy for effectively reducing the driving voltage of textile display devices.

Considering the structural compatibility between the device and the textile substrate, this work adopts a strategy of reducing the driving voltage by increasing the dielectric constant of the emissive layer. A highly transparent high-dielectric solution (HTDS) was used to replace conventional waterborne polyurethane as the matrix material, and BaTiO₃ was further introduced for synergistic optimization, with the aim of simultaneously improving the dielectric properties and luminescent performance of the device, thereby significantly lowering the driving voltage and substantially enhancing the luminance^38,39. To endow the device with anti-counterfeiting functionality, blue phosphor (ZnS: Cu) and orange phosphor (ZnS: Mn) were blended, and multicolor luminescent fibers (MCFs) were fabricated through a low-cost dip-coating process. The resulting fibers emit stable blue light under electric-field excitation and bright orange light under 360 nm ultraviolet excitation, thereby enabling dual-mode dynamic anti-counterfeiting^40,41. Performance tests show that the fabricated multicolor fiber device exhibits a turn-on voltage as low as 45 V and a luminance of 90 cd·m⁻² at 4 V/μm, while still maintaining excellent luminescent stability after 10,000 bending cycles. This work overcomes the high-voltage bottleneck of conventional ACEL textile displays and integrates low-voltage driving with multifunctional anti-counterfeiting capability, thereby providing a new technical strategy for the development of safe, flexible, and high-performance wearable smart textiles.

Results and discussion

Preparation of MCF display

The AC textile display based on the MCF achieves the dual mode driving (EL and PL) by precisely regulating the component ratio of the MCF display layer, which providing a richer information and multi-functional anti-counterfeiting for AC textile, as presented in Fig. 1. The coaxial flexible ACEL fibers were fabricated through a brief and easy dip-coating method. For textile display, it is important to achieve the inner fiber display with excellent flexibility and luminance. Hence, each functional layer of ACEL fiber possessed decent flexibility in our fiber device, such as inner electrode layer, dielectric layer, display layer, outer electrode layer, and encapsulation layer. As shown in Fig. 1, the inner electrode adopted an Ag electrode with ideal conductivity and excellent mechanical stability. The dielectric layer can fill the gaps between the electrode and the display layer, prevent short circuits caused by direct contact between the upper and lower electrodes, and ensure the stable operation of the device under alternating current driving. The WPU exhibits moderate dielectric constant (3–8), high volume resistivity (10¹²–10¹⁴ Ω·cm), and a good elongation at break (> 200%)⁴², which is an ideal dielectric layer.

Fig. 1. Schematic illustration of the fabrication protocol of the MCF.

To meet the demands of full-color and alternating current (AC)-driven optical fiber displays, blue phosphor ZnS: Cu, orange phosphor ZnS: Mn, BaTiO₃, and high-transparency high-dielectric solution (HTDS) were blended into a composite slurry to construct a single-layer stacked display layer. The solution exhibits a visible-light transmittance of ~95% and a relative dielectric constant of ~25, which simultaneously enhances device brightness and reduces the operating voltage. The dual-color phosphors endow the fiber display layer with multi-color emission. To ensure favorable display performance, highly transparent and conductive flexible PEDOT: PSS was adopted as the outer electrode, and its conductivity was further promoted by methanol treatment. Moreover, PDMS elastomer was utilized for device encapsulation to improve the stability of ACEL fiber displays, benefiting from its high transmittance, flexibility, and hydrophobicity⁴⁶. All functional layers were fabricated via a fully solution-processed dip-coating route, enabling the scalable production of fiber-based ACEL display devices.

Structure and morphology of MCF display

To achieve the fiber multicolor display, we mixed blue (ZnS: Cu) and orange (ZnS: Mn) phosphors to fabricate a single-layer emitting layer, as shown in Fig. 2a. In the composite emitting layer, the ZnS: Cu phosphors emit blue light under the electric field due to intrinsic heterojunctions within its crystal structure⁴³. However, the orange phosphor ZnS: Mn requires a relatively high electric field for activation. Therefore, the MCF emits blue light under electric field excitation. In addition, since the content of the orange phosphor is relatively higher than the blue phosphor in the composite display layer, the multicolor fiber emits orange light under UV light. As a result, the fiber achieves the blue and orange state switching under electric field and ultraviolet light switching, exhibiting excellent AC optical performance.

Fig. 2. The structure and morphology of MCF display.

a The luminescence mechanism of the fiber display. b The simulation of electric field distribution of the cross-section of CFD. c The cross-sectional SEM image of MCFB₁O₂. (Blue circle is ZnS: Cu, orange circle is ZnS: Mn). d The SEM image of MCFB₁O₂ (e) The cross-sectional fluorescence image of MCFB₁O₂ under the bright field image and dark field image. f The fluorescence image of MCFB₁O₂ under the bright field image and dark field image.

Compared with the single-strand inner core conductive layer, the twisted dual-strand conductive layer possessed superior bending and tensile performance, which is suited for flexible textile anti-counterfeiting applications. However, stress concentration occurs in the curved double-strand structure, which may destroy the device, as shown in Fig. S1a. Single-strand conductive layer exhibits uniform stress distribution during the bending process, but its bending and tensile performance are relatively lower. To balance the stress distribution and bending performance, we coated a dielectric layer (BTO) on dual-strand core conductive layer (Fig. S1b). This fabricated method significantly enhances bending performance compared with single-strand threads, while achieving more uniform stress distribution under deformation compared with uncoated dual-strand structures. In addition, a critical challenge with dual-strand conductive fiber is electric field non-uniformity across different cross-sections due to their spiral geometry, as presented in Fig. 2b. Based on the formula for human eye resolution, when the spacing between fiber protrusions is 0.1 mm, a uniform visual effect can be achieved at an observation distance of 0.344 m⁴⁴. Further increasing the electric field intensity can effectively improve the uniformity in periodic display, realizing the continuous display of fibers under close-range observation. Longitudinal side-view (Fig. S2) demonstrates that increasing the twisted density of the dual-strand conductive fiber can improve electric field homogeneity along the fiber axis. Therefore, we combine high-twisted density dual-strand cores with optimized dielectric coating layer. This enhancement of the helical structure can promote the uniform distribution of electric field and improve mechanical durability, meeting the requirements for electrical performance and textile flexibility in anti-counterfeiting applications.

The cross-sectional SEM images of MCFB (The fiber based on pure ZnS: Cu blue light powder) and MCFO (The fiber based on pure ZnS: Mn orange light powder) is exhibited in Fig. S3, where the particles size of ZnS: Cu and ZnS: Mn is about 20 µm and 5 µm, respectively. Additionally, the cross-sectional SEM image of MCFB₁O₂ is presented in Fig. 2c. The diameter of MCF is 1 mm, with the outer PDMS layer is nearly 100 µm in thickness. SEM images further reveal that both ZnS: Cu and ZnS: Mn particles coexist in the fiber display layer without obvious agglomeration, indicating that these particles can achieve uniform dispersion during the fiber preparation process. The horizontal SEM image of the MCFB₁O₂ is presented in Fig. 2d, where the fiber exhibits a glossy surface. This indicates that after PDMS coating, the device effectively enhances surface flatness.

Then, to investigate the luminescence property and morphology of MCF, fluorescence microscopy has been tested in bright and dark fields. The entire blue fiber MCFB exhibits uniform and stable blue fluorescent emission, which indicates that the phosphor ZnS: Cu can be well dispersed in the display layer, as exhibited in Fig. S4. In addition, we also tested the cross-sectional area of the MCF. The relatively consistent distribution of fluorescence intensity indicates that the preparation process of MCF would not affect the optical performance of the device. After mixing the orange phosphor, the sectional fluorescence microscopy of composite MCFB₁O₂ exhibits the blue and orange light emitting under UV light, indicating that the orange phosphors are also well-dispersed in the display layer, as shown in Fig. 2e, f. Besides, the luminous distribution of the orange light is consistent with the content of orange phosphor. The fluorescence microscopic results further indicate that the interfaces between various functional layers of the fiber display devices are tightly bonded, which is beneficial to driving the MCF.

The optoelectronic performance of MCF display

To investigate the optoelectronic performance of the MCF display, we have tested the photoluminescence (PL) spectra, electroluminescence (EL) spectra, and luminance. Figure 3a was the photograph of the different concentrations of phosphor under visual and UV light. As the orange phosphor content increases, the color of MCF gradually changes from blue to orange light. Each functional layer of the MCFs is sequentially coated by a simple and efficient dip-coating method, and this process has the capability to realize the mass production of luminescent fibers. At present, we have successfully prepared a roll of orange and blue display fibers, as shown in Fig. 3b. It is expected that scalable preparation can be achieved by further optimizing the equipment and processes.

Fig. 3. The optoelectronic properties of the MCF.

a The photographs of the MCF with different ratios of ZnS: Mn under visible and UV light. Scale bar: 1 cm. b The photographs of the MCFB₁O₂ under visible and UV light. Scale bar: 1 cm. c The PL spectrum of the MCF at different ratios of blue and orange phosphor. d The CIE color coordinates corresponding to the ACEL fiber with different composite phosphors. e Optical transmittance spectrum of the HTDS film. Scale bar: 1 cm. f Stress-strain curve of the ACEL fiber display for mechanical flexibility evaluation. Scale bar: 2 cm. g Electroluminescent (EL) luminance of MCFs with different matrix materials as a function of applied electric field. h Driving voltage characteristics of MCFs with different matrix materials.

For PL spectra, the pure blue and orange fiber exhibits the single fluorescence emission peaks in 480 nm and 580 nm, respectively, as shown in Fig. 3c, d. With the increase in the content of orange phosphor, the fluorescence emission peak shows a double peak at 480 nm and 580 nm. As the proportion of orange phosphor increases, the intensity of the emission peak at 580 nm gradually increases. Besides, the CIE coordinates of the blue fiber and orange fiber are (0.164, 0.300) and (0.455, 0.433) under the UV light, respectively. Under different mixing ratios of the two composite phosphors, their CIE coordinates show a nearly linear change from pure blue light to pure orange light, which is consistent with the photographs of MCF. It is worth noting that the fiber emits white light under the ratio of 1:1, which indicates the precise controllability of the mixed phosphor in color regulation and provides a basis for the multicolor design of the fiber display layer.

To systematically evaluate the performance of the high-transparency high-dielectric solution (HTDS) as the matrix material for MCF displays, we systematically characterized its optical, mechanical, and electroluminescent properties, as presented in Fig. 3e–h. Figure 3e shows the optical transmittance spectrum of the HTDS film. The HTDS matrix exhibits an ultrahigh transmittance of over 90% across the wavelength range (400–1200 nm), with the inset photograph further confirming its excellent optical clarity, which effectively minimizes optical loss and ensures high light output efficiency in the fiber display device. The ACEL fabric display can withstand a tensile strain of approximately 30%, which demonstrates the adequate intrinsic stretchability and mechanical properties of the full functional device, as shown in Fig. 3f. Besides, the ACEL fibre exhibits a fracture stress of nearly 150 MPa at a tensile strain of 33%, which ensures that the device resists structural failure under tensile deformations. Then, the Figure S5 presents the stress–strain curve of the HTDS film to assess its mechanical flexibility. The HTDS matrix demonstrates a maximum elongation of over 500% (5 times its original length) and a tensile strength of ~0.55 MPa, verifying its outstanding stretchability and mechanical robustness, which are essential for wearable fiber displays that require repeated bending and stretching. Figure 3g compares the electroluminescent (EL) luminance of MCFs based on different matrix materials (HTDS/BTO, HTDS, WPU/BTO, WPU) as a function of applied electric field. At the same electric field, the HTDS/BTO composite matrix delivers the highest luminance, followed by HTDS, WPU/BTO, and WPU, which confirms that the high dielectric constant and excellent dielectric properties of HTDS, when synergized with BTO ceramic filler, effectively enhance the EL performance of the device. Figure 3h illustrates the driving voltage characteristics of MCFs with different matrix materials. The driving voltage of the device is 65 V for the WPU matrix, 58 V for the WPU/BTO composite matrix, 54 V for the HTDS matrix, and only 45 V for the HTDS/BTO composite matrix. This result demonstrates that the introduction of HTDS and BTO can significantly reduce the operating voltage of the fiber display, which is critical for achieving low-voltage, safe, and stable operation in wearable electronic applications. While an operating threshold voltage of 45 V may still present potential biological risks to the human body, we have successfully demonstrated a monumental reduction in driving voltage compared to conventional 200 V ACEL textile display devices. Consequently, this work serves as an instrumental intermediary stage to develop wearable textile displays with lower, inherently safe operating voltages.

The electroluminescence spectrum would determine the color effect of the fabric display. Although the mix ratio of blue and orange phosphor is different within the luminescent layer, all of devices exhibited consistent blue electroluminescent emission at 460 nm under alternating current excitation, as present in Fig. 4a. The relative luminance intensity decreases as the orange phosphor content increases. Then, we further investigated the EL luminance performance of MCF under different driving voltages, as shown in Fig. 4b. The luminance of all MCFs increases with the increase of electric field, indicating that the electric field strength can effectively regulate the luminance and promote the recombination of carriers. In addition, the luminance of the MCF increased with the proportion of ZnS: Cu in phosphor mixture, demonstrating that the blue phosphor contributes more significantly to the luminance of the MCF. The luminance of MCFB₁O₂ reaches 90 cd·m⁻² under a driving electric field of 4 V/μm, exhibiting acceptable optoelectronic performance.

Fig. 4. The electroluminescence performance of the MCF.

a The EL spectrum of the MCF at different ratios of blue and orange phosphor. b The EL luminance of the MCF under different electric field intensities. c The CIE color coordinates corresponding to the ACEL fiber of MCFB₁O₂ under the EL and PL state. d Effect of observation angle on the brightness variation of ACEL fiber and the corresponding optical image. Scale bar: 2 mm. e Comparison of luminance, driving voltage and FoM of the MCF^{24,45,47–51}.

The CIE coordinates of the MCFB₁O₂ are (0.1943, 0.1993) and (0.3930, 0.3674) for the blue state originating from electroluminescent emission (under alternating current driving) and orange states originating from photoluminescent emission (under UV light), as present in Fig. 4c and Figure S6. Compared to other mix ratios of MCF, the long-distance between the blue (electroluminescent emission) and orange state is beneficial for the application of MCFB₁O₂ in AC devices. Since the enhanced color contrast is desirable for AC application in textile displays, we selected MCFB₁O₂ as the AC fiber to ensure the AC performance of MCF.

For phosphors ZnS: Cu and ZnS: Mn, the electric field intensity and driving frequency would affect the injection efficiency of electrons and holes. Then, to further explore the effect of the electric field on the performance of the MCF, we explore the EL spectrum and CIE color coordinates. The EL spectrum of the MCFB₁O₂ under different electric field intensities is present in Fig. S7. The results indicate that as the electric field intensity increases, the EL intensity increases significantly while the central emissive wavelength remains consistent. Besides, Fig. S8 characterize the driving frequency response of the MCFB₁O₂. The EL intensity increases with an increase of driving frequency under the same driving electric field intensity, reaching a maximum value at 40 kHz. Meanwhile, a blue shift in the central wavelength of the emission spectrum can be observed with the increase of alternating current driving frequency, from 495 nm at 1 kHz to 455 nm at 40 kHz. The CIE color coordinates of the MCFB₁O₂ are (0.3169, 0.3339) and (0.2315, 0.2345) for the 1 kHz and 40 kHz driving frequency. Considering the EL intensity and emissive wavelength, we choose 40 kHz as the driving frequency in the subsequent experiments.

A large viewing angle can ensure that observers can clearly see the accurate colors and stable brightness of the screen from different angles, thereby effectively enhancing the application effect and user experience of the device. The luminance of the MCF is almost unaffected by changing the viewing angle in 360°, which confirms the excellent luminous uniformity of the prepared ACEL fibers, as shown in Fig. 4d. Compared with planar display exhibiting significant angular dependence, the fabric display has a wider viewing angle and shows significant advantages in wearable and outdoor displays⁴⁵. A comprehensive comparison of our MCF with other works is presented in Fig. 4e, illustrating that our device has a lower driving electric field of 4 V/μm and acceptable luminance of 70 nit. The Figure of Merit (FOM) is defined as FOM = L/E, where L is luminance and E is driving electric field, and the FOM directly quantifies the luminance output per unit driving electric field. Although some reported works exhibit advantages in single performance dimensions, our device exhibits a favorable balance between driving electric field and luminance, and a relatively high level in the FOM metric, demonstrating competitive electric field utilization efficiency. In terms of devices, our fiber display exhibits good cyclic stability, a high AC performance, and dual-mode (EL and PL) emission switching, which is suitable for wearable anti-counterfeiting applications in the textile industry.

The stability and biocompatibility of the ACEL fiber display

To investigate the stability and biocompatibility of ACEL fiber display, the mechanical stability, long-term stability, 85 °C/85% RH aging experiment, and in vitro biocompatibility were test. The mechanical stability of MCF under bending deformation is prominent for wearable textile displays. To measure the mechanical stability, we have built the in-situ measure system which combines with the electrically controlled displacement stage and screen luminance meter. An electric bending apparatus was employed to repeatedly flex the MCF in order to systematically evaluate its cyclic stability. The test was conducted under a constant electric field of 2.4 V/µm, with the initial measured luminance set as the baseline. The relative luminance was measured and recorded after every 1000 bending cycles. As shown in Figs. S9, S10, the luminance of the device exhibited a gradual decline with increasing bending cycles, characterized as follows: after 3000 cycles, the relative luminance was 98.9%; after 6000 cycles, it decreased to 97.57%. Ultimately, even after 10,000 bending cycles, the relative luminance remained above 91.1%, with an attenuation strictly below 10%. This result fully demonstrates that the MCF can maintain excellent electroluminescent performance under rigorous mechanical deformation, exhibiting outstanding cyclic stability and mechanical durability. This provides critical assurance for its application in wearable devices that require frequent bending.

Furthermore, the long-term stability of the device benefits from its well-designed structure. The outermost PDMS encapsulation layer, as a hydrophobic material, not only effectively isolates moisture and oxygen, protecting the internal functional layers-particularly the PEDOT: PSS electrode—from erosion, but also enhances the overall mechanical robustness of the fiber. Thanks for this protection, the MCF can operate continuously and emit light stably for over 24 h even in underwater environments, as shown in Fig. S11. This significantly expands its potential for applications in wearable underwater displays and lighting. To evaluate the long-term stability of PDMS-encapsulated ACEL fiber display device, the accelerated aging experiments (85 °C/ 85%) was test for 7 consecutive days, as shown in Fig. S12. Even after one week of continuous high-temperature and high-humidity aging, the ACEL fiber device still retains approximately 80% of its initial luminescence intensity. The attenuation of the aging period verifies that the PDMS encapsulation layer can endow the fiber display with favorable anti-aging stability under hot and humid harsh environments.

To investigated the long-term stability of ACEL fiber display, the relative luminance of ACEL fiber display was tested everyday under the driving electric fields of 1.6, 2.4 and 3.6 V/μm, as shown in Fig. S13. The ACEL display retained over 90% of their original relative luminance after 7 days, illustrated that the fiber display possesses long-term stability under the different driving condition. Then, the long-term stability of ACEL fiber was test under maintain EL state and infrared thermal camera image, as shown in Fig. S14, S15. Within the first 3 hours of sustained EL operation, the relative luminance of the ACEL fiber maintains above 95% of the initial value, showing negligible luminance attenuation. Even after 6 h of uninterrupted driving, the device still retains over 83% of its original luminance. After 13 h of continuous operation, the luminance of the fiber display declines to ~50% of the initial value, demonstrating the long-term stability and practical usability of ACEL fiber display. Besides, the surface temperature of the fiber display device was test by infrared thermal camera during long-term continuous operation. The surface temperature of fiber display device rose from an initial 26.3 °C to 29 °C within 30 s, with a mere temperature increment of 2.7 °C. After 6 hours of continuous illumination, the temperature of the fiber display remained stable at approximately 29 °C. This result demonstrates the ideal thermal stability of the device, eliminating potential risks such as high-temperature burns or reduced wearing comfort.

For a wearable device, the textile displays close contact with the skin is inevitable. To investigate the biocompatibility of wearable textile displays, the in vitro cell experiment and cell staining experiment have test, as shown in Figure S16 and Table S2. The result demonstrated that the HTDS and ACEL textile display possess favorable cytocompatibility and negligible cytotoxicity.

Potential application of the MCF display

MCF exhibits significant potential for application in high-security textile anti-counterfeiting due to its unique dual-mode (PL and EL) emission switching combined with exceptional flexibility. The long distance between the blue (EL state) and orange state (PL state) of MCFB₁O₂ is conducive to the AC application. In ambient light, the encryption information remains invisible, ensuring the information’s confidentiality. Through the synergistic effect of multifunctional AC, the information privacy and difficulty in replication of AC devices can be further enhanced. As an application example, MCFB₁O₂ is woven together into a wool sweater to form a multicolor textile, exhibited in Fig. 5a. The textile was woven by combining the traditional yarn fiber with display fiber, and through the design of specific weaving patterns, realizing dual-mode anti-counterfeiting applications in wearable fabrics.

Fig. 5. The AC application based on the MCF.

a Schematic illustration of the AC textile display MCF fabricated by sewing technology. b The AC application based on the MCF. Scale bar: 1 cm. c The wearable MCF for AC application. Scale bar: 1 cm.

To extend the MCF in AC applications, we have fabricated a multifunctional AC device that can realize multimode display under the switching of electric field and UV light. For AC textile, we woven the number “5” pattern with MCF in the number “8” pattern, and the other two places were woven with pure blue fiber, as shown in Fig. 5b. The AC textile can achieve the blue number “8” pattern under the alternating current electric field driving and the blue number “5” pattern under the UV light. Meanwhile, the logo “WTU” was fabricated by blue fiber “WT” and MCF “U”. The logo appears entirely blue “WTU” pattern under the alternating current electric field driving, while it appears the blue “WT” pattern and the white-yellow “U” pattern under UV light. Consequently, dual-mode MCF demonstrates the excellent AC capabilities, effectively hiding confidential information. In daily life, the movement of human joints causes repeated bending and stretching of wearable textiles. Therefore, the flexibility of the fibers is an important factor in ensuring both wearing comfort and device stability. As shown in Fig. 5b, the MCF is integrated onto the fabric through sewing technology, which benefits from the flexibility of the fiber. The MCF’s excellent conformability ensures contact with the skin, thereby enhancing the robustness and user convenience of the wearable anti-counterfeiting device.

Furthermore, we fabricated a wearable AC textile and wore it on the dorsal hand joint, as exhibited in Fig. 5c. The ACEL’s intrinsic luminance of PL-only mode is remarkably higher than EL-only mode, and the luminance of the ACEL fiber under the dual mode is entirely governed by the PL mechanism. Therefore, the luminescent signal of the combined EL + PL mode is dominated by the PL signal. Then, the AC textile presents the blue number “8” pattern under the alternating current electric field driving and blue number “5” pattern under the UV light, demonstrating its excellent anti-counterfeiting performance and robust EL performance under mechanical stress. In addition, Fig. S17 demonstrating the AC textile based on MCFB₁O₂ remained blue emission under different states of deformation (twisting, bending), indicating that its optoelectronic performance is stable under various mechanical deformations. The integration of dual-mode emission within a single fiber provides a solution for wearable textile anti-counterfeiting technology, which can simultaneously enhance both the privacy protection capability and the level of information encryption.

Conclusion

In conclusion, this study successfully developed a low-voltage-driven alternating-current electroluminescent (ACEL) textile anti-counterfeiting display device based on a highly transparent high-dielectric solution (HTDS)/barium titanate (BTO) composite dielectric system, offering an effective strategy for integrating wearable flexible optoelectronics with information security technologies. The results show that the introduction of high-dielectric HTDS and BTO nanoparticles into the luminescent fiber system significantly improves the internal electric-field distribution and dielectric properties of the device, thereby reducing the driving voltage to 45 V. This value is substantially lower than that of conventional waterborne polyurethane (WPU)-based devices, enabling high-performance flexible luminescent display while improving operational safety for wearable applications. The fabricated multicolor luminescent fiber (MCF) device exhibits excellent mechanical flexibility and stability, with nearly negligible luminance decay after 10,000 bending cycles, and achieves a high luminance of 90 cd·m⁻² at an electric field of only 4 V/μm, demonstrating its reliability for wearable use. In addition, by combining electric-field excitation with ultraviolet-responsive behavior, the fiber device realizes reversible switching between blue electroluminescence and orange emission, thereby establishing highly distinguishable dynamic anti-counterfeiting characteristics. This multifunctional anti-counterfeiting capability overcomes the limitations of conventional static anti-counterfeiting strategies and demonstrates strong potential for applications in high-end wearable textiles, smart garments, and information encryption.

Experimental

Materials

The conductive substrate was silver-coated sewing thread (800D, Dongguan Shengxin Special Rope Webbing Co., Ltd.), hereafter referred to as Ag-coated thread. The polymer matrix was a waterborne polyurethane (WPU, Macklin Biochemical Technology Co., Ltd.) solution (60 wt%). Propylene carbonate (PC) was purchased from Energy Chemical. 1-Hydroxycyclohexyl phenyl ketone (photoinitiator 184) and 4-acryloylmorpholine (ACMO) were obtained from Macklin Biochemical Co., Ltd. Polyurethane acrylate (RJ4247, PUA) was supplied by RYOJI Chemical. The dielectric material comprised barium titanate nanoparticles (BaTiO₃ NPs, Macklin Biochemical Technology Co., Ltd.). The luminescent layers of ACEL phosphors of ZnS: Cu and ZnS: Mn are purchased from Shanghai Keyan Phosphor Technology Co., Ltd.). The external electrode was formed using a solution consisting of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS, Niche Fine Technology Co., Ltd.), isopropanol (IPA, Sinopharm Chemical Reagent Co., Ltd.), and dimethyl sulfoxide (DMSO, Shanghai Aladdin Biochemical Technology Co., Ltd.). PDMS (Polydimethylsiloxane) elastomer (Sylgard 184) was purchased from Dow Corning Inc. All reagents were used as received and were not further purified.

Dielectric layer preparation

The dielectric layer coating solution was prepared by mixing BaTiO₃ NPs with the 60 wt% WPU solution at a mass ratio of 1:3 (NPs: WPU). The Ag-coated thread was immersed into the dielectric solution, withdrawn through a cylindrical mold (0.3 mm inner diameter) at a controlled speed to control coating thickness, and subsequently air-dried under ambient conditions for 30 min.

Preparation of luminescent layers

The photoinitiator 184 (1-hydroxycyclohexyl phenyl ketone), ACMO (acryloyl morpholine), PC (propylene carbonate), and PUA (polyurethane acrylate RJ4247) are stirred and mixed in a predetermined ratio, followed by standing for defoaming to obtain the base solution for the luminescent layer. ZnS: Cu, ZnS: Mn, and BaTiO₃ phosphor powders are blended according to a predefined mass ratio. The mixed ACEL phosphors are uniformly dispersed into the luminescent layer base solution to form the coating solution for the luminescent layer. A pre-coated dielectric layer on a silver-plated wire is immersed into the luminescent layer solution, withdrawn at a controlled speed through a cylindrical mold, and subsequently cured under a UV lamp for 30 min.

Preparation of external electrode

The external electrode coating solution was prepared by blending DMSO, IPA, and PEDOT: PSS in optimized mass ratios. The Ag-coated thread with pre-deposited dielectric and luminescent layers was immersed into the external electrode solution, carefully withdrawn, and evenly coated using the cylindrical mold, then air-dried under ambient conditions for 10 min.

The electric field and mechanical simulation of the ACEL fiber display

All steady-state simulations were performed using COMSOL Multiphysics, including 2D electric field simulation and 3D mechanical simulation. The 2D electric field simulation was conducted with the Electric Currents interface and stationary solver, using two cross-sectional models to investigate the effects of twin-stranded electrode structure and helical turn number on electric field distribution. The 3D mechanical simulation was performed with the Solid Mechanics interface and stationary solver, to analyze the tensile performance and stress distribution of single/twin-stranded fibers, as well as the optimization effect of the dielectric buffer layer. The physical parameters of the materials in COMSOL Multiphysics were used as listed in Tables S3 and S4.

Characterization

Cross-sectional fluorescence images of the device were acquired using a fluorescence microscope (BX53F2, OLYMPUS). Scanning electron microscopy (SEM) was performed on a Hitachi SU 5000 with an accelerating voltage of 10.0 kV. The ACEL device was driven by a voltage signal generated from an arbitrary waveform generator (SIGLENT SDG1032X) and amplified via a high-voltage amplifier (Pintech HA-820A). ACEL fiber luminance was characterized using a screen luminance meter (Sanpometer SM218E), while spectral data acquisition employed a fiber-optic spectrometer (Ideaoptics PG2000 Pro). The surface temperature of fiber display device was test by the thermal imaging camera (Uni-Trend Technology (China), UTi260B + ). The accelerated aging experiments for textile display devices were performed using an environmental chamber (YGDSJ800-40, Shenzhen Yutai Test Equipment Co., Ltd.) at 85 °C / 85% RH. Bending stability of the fiber display device was evaluated under cyclic mechanical deformation using a custom-built motorized stretching stage (SNOWIT). Finite element analysis of the device’s three-layer structure, performed in COMSOL Multiphysics software, simulated the electric field distribution.

Author contributions

G. Liu conceived the idea, designed the research, analyzed the data, and wrote the manuscript, supervised, and managed the research. Y. Yang participated in the experiments, figure revision, and manuscript writing. Z. Xue participated in the experiments. Z. Qiu, R. He and M. Hu revised the manuscript. M. Tang supervised and managed the research. K. Liu supervised and managed the research. All authors discussed the results and contributed to the writing and revision of the manuscript. All authors approved the final version of the manuscript.

Peer review

Peer review information

Communications Chemistry thanks Yongmin Jeon and Young Woo Kim for their contribution to the peer review of this work. A peer review file is available.

Funding

This work was supported by the Natural Science Foundation of Hubei Province (2026AFB286), the Scientific Research Project from the Education Department of Hubei Province (Q20251628), National Key Research and Development Program (2021YFB3801000), Innovative Research Groups of Hubei Province (2022CFA038).

Data availability

All data are available in the Article or its Supplementary Information. Supplementary data relevant for this publication are provided with this paper.

Competing interests

The authors declare no competing interests.

Supplementary information

The online version contains supplementary material available at https://doi.org/10.1038/s42004-026-02214-0.