In general, in optoelectronic devices consisting of layers such as semiconductors, electrodes, and insulating films, the performance of the device varies greatly depending on the size and structure of the electrodes. To make a fibrous electronic device, it bends easily and the device must be formed on a thin wire, so that the size of the device cannot be made larger than the thickness of the wire in micrometer units, so that there is a limit to improving device performance.
However, it is recently an issue that a national research team has developed a technology that improves performance beyond these limits. Korea Institute of Science and Technology (KIST) Next Generation Semiconductor Research Institute Hyun-Jung Lee and Jeong-A Lim The research team produces the desired electrode by printing it with an inkjet printer and winds the wire of the electrode coated with a semiconductor on it, and coils the desired electrode structure. It has developed a technology that makes it possible to manufacture fiber electronic devices, such as diodes.
In 2019, the team of Dr. Hyun-Jung Lee developed a technology that printed carbon nanotube (CNT) ink on a hydrogel substrate, which is a water-containing polymer, and then transferred it to form an electrode on the desired surface.
The CNT electrode printed on the hydrogel is like floating in water and it is expected that if the fiber is rolled into it, it can be easily transferred to the surface of the fiber without damaging the structure of the electrode. . As a result of the research with Dr. The Jeong-ah Lim equipment, the real semiconductor layer and CNT A high-performance fibrous device was manufactured without damaging the electrode.
The fibrous transistor wrapped with the developed CNT electrode maintained a stable performance of over 80%, even when bent at a bending radius of 1.75 mm. In addition, by using the translucent properties of the CNT electrode, he was able to manufacture a fiber photodiode that can detect light by wrapping the electrode seal coated with a semiconductor layer that can generate current by absorbing light with a CNT electrode.
The manufactured fibrous photodiode can detect light in a wide range of visible light and has an excellent sensitivity that is not inferior to that of flat devices. When the fiber photodiode developed by the research team is inserted into a cloth with an LED element and worn like a glove, the fiber photodiode detects the reflection intensity of the LED light that changes according to the change in the amount of blood flowing from the fingertips to measure the user’s pulse.
Dr. Lim Jeong-ah, of KIST, explained: “The glove-type heart rate monitor replaces the caliper-type heart rate meter, so you can easily approach the person with a comfortable, soft feeling and have the ‘advantage of being able to to measure heart rate in real time anywhere and anytime.’
Dr. Hyun-Jung Lee said, “This research presents a new approach to electrode formation technology, which remains a task in the development of fiber devices, and can accelerate the development of fiber-optic electronic devices with circuits. complex, from improving the performance of fiber optoelectronic devices. I’m looking forward to “.
On the other hand, this research was carried out as a major KIST project under the support of the Ministry of Science and ICT, as well as a mid-level follow-up study by the National Research Foundation of Korea and an original nanomaterials. technological development project, and was published in the latest issue of the international academic journal ACS Nano.
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Reporter Oh Sang-mi [email protected]