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DGIST developed the world’s first electronic skin with a mesh structure that allows for long-term attachment with no discomfort

  • 조회. 1012
  • 등록일. 2022.10.09
  • 작성자. External Relations Team

 - A research team led by Professor Lee Sungwon from DGIST succeeded in developing the world’s first mesh (nanomesh) structured electronic skin device (organic field-effect transistor) 

- An electronic skin device comprising only a mesh (nanomesh) structure that can measure and process bio-signals for a prolonged period indicates a big step toward integrated systems for electronic skin devices. 

 

 The research team led by professor Lee Sungwon from the Department of physics and chemistry at DGIST (President Kuk Yang) succeeded in developing the worlds first ultrathin and breathable nanomesh (mesh) organic field-effect transistor (OFET) that can be applied to electronic skin devices. Nanomesh OFET, in combination with various sensors, is expected to enable direct measurement of physiological data from the skin surface and optimize data processing.

 Electronic skin refers to electronic wearable devices worn on the skin to collect biosignals, such as temperature, heart rate, electromyogram, and blood pressure, and transfer the data. Owing to the recent increase in interest in smart healthcare systems with wearable devices, related technologies are being actively developed. A soft sensor that can attach to smooth and constantly moving skin surfaces is required to accurately measure physiological signals using a real-time health care system. As a result, most electronic devices worn on the skin surface have been manufactured using substrates with flat surfaces such as plastic and rubber.

 However, long-term attachment of substrate with flat surface structure and low liquid and vapor permeability to biological skin can cause unexpected diseases to occur (such as atopy, metabolic disorders, among others).  Hence, it is necessary for electronic devices that come in contact with biological tissues to achieve high permeability to ensure long-term use. Accordingly, research on polymer nanofiber-based nanomesh devices with good permeability has been attracting considerable attention. 

 The research team led by Lee Sungwon at DGIST developed an ultra-thin nanomesh OFET that causes almost no discomfort for the users and can be combined with various sensors. In particular, the developed OFET device showed consistent functions even when folded or curved, with almost no performance degradations, even in severe environments such as ³1,000 deformations and high humidity.

 Manufacturing nanomesh transistors was difficult owing to the rough surface and lack of mechanical robustness and thermal and chemical stability. Professor Lee Sungwons team solved these problems simultaneously by using a material called Parylene C[1]as a biocompatible coating. In addition, the conventional vacuum deposition method[2] was used for simpler processing instead of synthesizing or high-temperature processing.

 Professor Lee Sungwon from the Department of physics and chemistry at DGIST said, We have successfully developed a nanomesh organic field-effect transistor for the first time and demonstrated an integrated active-matrix tactile sensor. The development of transistors was essential for building a complex circuit, and now with the nanomesh electronic skin device, long-term measurement and processing of physiological data in real time is possible.

 This research has been published in Advanced Functional Materials, a well-known international academic journal in the field of Nanoscience & Nanotechnology.

 

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Summary of Research Outcomes

All-nanofiber-based Substrate-less, Extremely Conformal, and Breathable Organic Field Effect Transistor for Biomedical Applications

Gihyeok Gwon, Hyeokjoo Choi, Jihoon Bae, Nora Asyikin Binti Zulkifli, Wooseong Jeong, Seungsun Yoo, Dong Choon Hyun, and Sungwon Lee

(Advanced Functional Materials, online published on 06.26, 2022)

 

   Nanomesh-based electronic devices have been attracting considerable attention as they enable conformal contact with a complex surface, with outstanding flexibility and vapor permeability. However, building a complex electronic device based on nanomesh structure has been limited in practical utilization owing to the relatively inferior mechanical properties and difficulties in processing. For such nanofiber-based devices to achieve system-level applications, integrations with organic field-effect transistor (OFET) devices and various sensors are requireda key factor of a nanomesh-based integrated system. This research demonstrated, for the first time, a biocompatible, ultra-thin (~1.5 μm), ultra-light (1.85 g/m2) nanomesh-based OFET with excellent mechanical durability that can make conformal contact with curved skin. The developed OFET showed excellent electrical properties with an on/off ratio of 3.02 × 104 ±0.9 × 104, mobility of 0.05 ±0.02 cm2V-1s-1, subthreshold slope of 1.7 ±0.2 V/Decade, and threshold voltage of 6 ±0.5 V. Crack initiation mechanism was investigated through simulation using the COSMOL program to understand the deformations of nanomesh transistor. Moreover, an integrated active-matrix tactile sensor was successfully demonstrated, suggesting a potential application in the field of biomedical electronics.

 

 

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Q&A Research Outcomes

Q. What is different about this achievement?

Existing transistor devices built as switches for electronic skin devices were inappropriate because they were manufactured with flat substrates and could cause unexpected diseases with long-term use. In this study, we developed the worlds first nanomesh-based OFET with high permeability and built a system that can collect biosignals in the long term.

Q. Where can this achievement be applied?

Applications of nanomesh-based electronic devices were limited in terms of building complex electronic devices owing to a lack of development in transistors. However, with this research, integration with electronic skin devices that require long-term use and construction of complex circuits has become possible.

Q. How much time and what other tasks remain until commercialization?

New nanomesh structured devices are continuously being developed, with various studies in progress. However, a nanomesh energy storage device is yet to be developed, and external power is still required. With the development of nanomesh-based energy storage devices, an integrated electronic device composed only of nanomesh will be available for commercialization in near future.

Q. How did you start your study?

We started this research to develop wearable electronic devices that can measure and process biosignals. We plan to develop more electronic devices in the future.

Q. What is the significance of this study?

Many studies have been conducted with recently developed nanomesh-based devices that have excellent permeability, enabling long-term use on the human body. However, due to rough surfaces, building complex circuits and practical applications were limited. In this study, we demonstrated, for the first time, a nanomesh-based OFET that can make conformal contact with the human skin, suggesting that implementing complex circuits by integrating various nanomesh devices will soon be possible, indicating a potential application in the field of biomedical electronics. 

Q. What is the goal you wish to achieve?

Our research team aimed to develop a single integrated telemedicine system. We plan to build 1) a platform that can diagnose health without external power by developing a flexible and wearable energy storage device that can store energy obtained using an energy harvester, and 2) a sensor that can measure and transmit physiological signal data using the stored energy.

 

 

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Description of Figures

[Figure 1] Nanomesh-based Organic Field-Effect Transistor

 Nanomesh-based OFET is manufactured using the conventional vacuum deposition method in a relatively simple process. This device is ultra-thin (~1.5 ) and ultra-light (1.85 g/m2), has excellent permeability, and is appropriate for long-term measurement and processing of physiological signs.

 

[Figure 2] Integrated active-matrix tactile sensor

 Integrated tactile sensors of various sizes were demonstrated. Electrical and mechanical properties were excellent and implementing complex circuits in combination with various sensors appears possible.

 

 

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For more information, contact:
Lee, Sungwon
Department of Physics and chemistry
Daegu Gyeongbuk Institute of Science and Technology (DGIST)
E-mail: swlee@dgist.ac.kr

Associated Links
Research Paper on Advanced Functional Materials
https://doi.org/10.1002/adfm.202204645

Journal Reference
Gihyeok Gwon,Hyeokjoo Choi,Jihoon Bae,Nora Asyikin Binti Zulkifli,Wooseong Jeong,Seungsun Yoo,Dong Choon Hyun,Sungwon Lee, "An All-Nanofiber-Based Substrate-Less, Extremely Conformal, and Breathable Organic Field Effect Transistor for Biomedical Applications", online published on 06.26,2022.