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In the Internet of Things (IoT) environment, there is a growing demand for wearable display devices, which must not only be portable and functional, but also have low energy consumption. Electronic paper displays have the advantages of low power consumption and good outdoor display adaptability, and stand out among many display devices. Electrospun Nanofbers are known for their lightness, flexibility, and customizability. Wearable fibers that integrate electronic paper display technology have not yet been reported.
Recently, the team of Professors Deng Shaozhi and Yang Bairu of Sun Yat-sen University published a research result entitled "Ultra-Low Power Consumption Coaxial-Structured Electrophoretic Display Fibers with Stretchability and Environmental Adaptability" in Advanced Fiber Materials. The electrophoretic electronic paper display fiber (EPDF) proposed in this work consists of a PDMS (polydimethylsiloxane) fiber substrate, an electrophoretic microcapsule display layer, AgNWs internal and external electrodes, and an insulating PDMS package. Thanks to the bistable characteristics of the electrophoretic electronic paper display, the fiber device has low energy consumption and has the advantages of low cost, light weight, stretchability and strength (>1000 stretching cycles). It has a contrast ratio of 7.8 under ambient light and can realize information display on the surface of traditional clothing. It is expected to be used in outdoor wearables and Internet of Things displays.
The main point of this paper
Electrophoretic electronic paper is one of the most widely used reflective display devices. Its unique bistable property enables it to display patterns and information without continuous power supply, making it suitable for outdoor wearable displays.
The device uses PDMS fiber as the substrate, and uses the dip-coating method to sequentially prepare the AgNWs inner electrode, electrophoretic microcapsule display layer, AgNWs:HPMC outer electrode and insulating PDMS package to obtain a coaxial electrophoretic electronic paper display fiber (EPDF), as shown in Figure 1.
The intrinsically hydrophobic PDMS substrate becomes hydrophilic after surface treatment (ultraviolet ozone treatment and mechanical stretching). This is because the surface treatment produces dense microcracks and increases the surface roughness. AgNWs electrodes can be prepared on the surface by dip coating. The conductivity (20 Ω/mm) and robustness (>1500 stretching cycles) of the inner electrode are excellent, as shown in Figure 2.
The operating voltage of the EPDF device is a human safety voltage, and the best display state can be achieved when driven by a 30 V DC voltage. In addition, the team used different driving voltage waveforms to prove that the device has excellent bistability and fast black-white state switching speed (0.412 s from black to white and 0.391 s from white to black when driven by 30 V), as shown in Figure 3.
Under 30 V voltage drive, the stable reflectivity of EPDF is about (30.1±0.05) in the white state and about (3.8±0.1) in the black state, and the device contrast is about 7.8. The one-dimensional structure of EPDF shows consistent characteristics in all directions, and the contrast is almost unaffected by the viewing angle (7.5-7.8). The black and white states of EPDF are clearly visible to the naked eye, as shown in Figure 4.
EPDF can still maintain its function under strain greater than 50%. After 1000 stretching cycles, the device can still work normally, and the contrast remains above 6.5, proving that the device has excellent reliability. In addition, the water immersion experiment and infrared light irradiation experiment respectively demonstrated the washability and temperature regulation of EPDF. The researchers further wove EPDFs and traditional clothing together to form a seven-segment code that can display letters and numbers, demonstrating the application prospects of EPDF in the field of outdoor wearable displays, as shown in Figure 5.
In summary, low energy consumption is an ideal characteristic of wearable display devices. The team combined the electrophoretic electronic paper display with bistable characteristics with the fiber matrix to design and prepare an electrophoretic electronic paper display fiber device (EPDF). This coaxial fiber display device is a reflective display device that can achieve extremely low energy consumption outdoor display, and exhibits a uniform contrast ratio (about 7.8) that is independent of the viewing angle at a human safety voltage of 30 V, as well as excellent bistable. EPDF can be bent to cover the surface of the human body, and has the advantages of being stretchable and washable, which opens up new ideas for the development of wearable smart clothing for outdoor low-energy display.
Electrospinning Nanofibers Article Source:
https://link.springer.com/article/10.1007/s42765-024-00455-z
