Saturday , March 6 2021

The new generation semiconductor research institute KIST develops electronic fiber that allows you to measure your heart rate with your fingertips



▲ Korea Institute of Science and Technology (KIST) Next Generation Semiconductor Research Institute Dr. 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 rolls the desired electrode structure. He has developed a technology that allows the manufacture of fibrous electronic devices such as photodiodes.
[기계신문] With the development of portable devices, E-textile technology, which combines light and comfortable fibers with smart electronic devices, is attracting attention as a new generation technology. In particular, a fiber electronic device that has electrical characteristics and maintains the characteristics inherent in a fiber is one of the key devices for implementing an electronic fiber.

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.

▲ A schematic diagram of a strategy to implement a photoelectric device to control signals from the human body by transferring CNT electrodes. The electrode is transferred by printing the electrode on the hydrogel and rolling the fiber on the electrode (left). The photodiode manufactured by the transfer process is inserted into the fiber and a schematic diagram is applied to the optical measurement of blood flow at the fingertip the actual characteristics of heart rate measurement (right)

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.

▲ (a) CNT electrode transfer process to implement a fibrous device developed by the research team, (b) A photo of the electrode of the desired size wrapped around the wire using technology developed by the research team

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.’

▲ When the fiber photodiode developed by the research team is inserted into a cloth with the LED element and worn like a glove, the fiber photodiode detects the intensity of the reflection of the LED light that changes according to the change in the amount of blood flowing from the fingertips and measuring the user’s pulse

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]

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