By BizLED Bureau
September 24, 2015: In the near future, our clothes will light up, even change color. Thanks to a new technology developed by a team of researchers from Fudan University, Shanghai, China, and the University of California at Los Angeles, the United States. In an article published in the journal Nature Photonics , they talk about a concept of light fiber that is so thin and flexible that it could be integrated into a fabric.
On the other hand, with the demand for wearable electronics like devices for monitoring fitness and health are picking up, the industry feels the need for flexible light-emitting devices and materials.
Researchers were, therefore, keen to develop fabrics that can integrate light-emitting devices. But, fabric is not a suitable light-emitting material. However, some scientists have found a way and have directly integrated light-emitting devices into fabrics by using a new technology called polymer light-emitting electrochemical cells (PLECs).
PLECs are composed of two metal electrodes connected to a thin organic layer that acts as a semiconductor. PLECs have many benefits as mobile ions are incorporated into the semiconductor. They have high efficiency in converting electrons to photons, low operating voltage, and high power efficiency. PLECs also do not require the use of metals and they can be used on rough surfaces, too. These properties make PLEDs suitable for large-scale manufacturing.
These fiber-shaped PLECs have a coaxial structure with four layers. Using a solution-based processing, a steel wire, which acts as the base of this fiber, is dip-coated with a thin layer of ZnO nanoparticles. This layer has two key functions: protecting the light-emitting layer that’s applied next; and decreasing the leakage of the current, thus enhancing current efficiency.
Next, the electroluminescent polymer layer is deposited onto the wire using dip-coating. Finally, a sheet of aligned carbon nanotubes is wrapped around the bundle using a dry-drawn form of spinnable carbon nanotubes. Because the carbon nanotubes were highly aligned, they provided the fiber with high electrical conductivities. Imaging revealed that the fibers had a uniform diameter and a smooth outer surface.
The scientists who created these fibers determined the lifetime of the devices. They found that the fibers gradually light up over a 21-minute period and gradually dim over a four-hour period; in these studies, the light emitted by the fibers was blue. The fiber lit up when a voltage of 5.6V was applied and reached a peak intensity at 13V. When the fiber is pre-charged, it displays a rapid turn-on response that is similar to conventional LEDs.
The researchers discovered that the fibers slowly light up and takes about 21 minutes to do so. They then slowly dim over 4 hours. It was also found that the fibers emit blue light, but the researchers believe that other colors can be displayed as well. When a voltage of 5.6V is applied that reach 13V, the fibers light up. If the fibers are bent, they maintain their brightness of about 90%. percent and no obvious damage was observed.
The researchers concluded that the light-emitting fibers can be woven into fabrics without compromising any luminescence. Hence, these fabrics can be used develop wearable electronics and other fabric-based electronics.
Source: Nature Photonics
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