Hae-Ryung Lee

Seoul National University

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Jeong‐Yun Sun

Seoul National University

Young‐Chang Joo

Seoul National University

Seungmin Lim

Kangwon National University

Kyu Hwan Oh

Seoul National University

Chan Jin Park

Seoul National University

Hyunjae Yoo

Seoul National University

Jonghyun Ha

Ajou University

Taek Dong Chung

Seoul National University

Ho‐Young Kim

Seoul National University

Keunhwan Park

Gachon University

Cooperative Institutions

Seoul National University

Seoul Institute

University of Seoul

Government of the Republic of Korea

Samsung (South Korea)

Advanced Institute of Convergence Technology

Technical University of Denmark

University of Illinois Urbana-Champaign

Pohang University of Science and Technology

Seoul National University of Science and Technology

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Ion-to-ion amplification through an open-junction ionic diode

Proceedings of the National Academy of Sciences (2019)

Seungmin Lim Hyunjae Yoo Min-Ah Oh Seok Hee Han Hae-Ryung Lee

As biological signals are mainly based on ion transport, the differences in signal carriers have become a major issue for the intimate communication between electrical devices and biological areas. In this respect, an ionic device which can directly interpret ionic signals from biological systems needs to be designed. Particularly, it is also required to amplify the ionic signals for effective signal processing, since the amount of ions acquired from biological systems is very small. Here, we report the signal amplification in ionic systems as well as sensing through the modified design of polyelectrolyte hydrogel-based ionic diodes. By designing an open-junction structure, ionic signals from the external environment can be directly transmitted to an ionic diode. Moreover, the minute ionic signals injected into the devices can also be amplified to a large amount of ions. The signal transduction mechanism of the ion-to-ion amplification is suggested and clearly verified by revealing the generation of breakdown ionic currents during an ion injection. Subsequently, various methods for enhancing the amplification are suggested.

SIGNAL (programming language)

10.1073/pnas.1903900116

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Citations (55)

Columnar grown copper films on polyimides strained beyond 100%

Scientific Reports (2015)

Jeong‐Yun Sun Hae-Ryung Lee Kyu Hwan Oh

Abstract Many flexible electronic devices contain metal films on polymer substrates to satisfy requirements for both electrical conductivity and mechanical durability. Despite numerous trials to date, the stretchability of metal interconnects remains an issue. In this paper, we have demonstrated a stretchable metal interconnect through control of the texture of a copper film with columnar grown grains on a polyimide (PI) substrate. The columnar grown copper films (CGC films) were deposited by regulating radio frequency (RF) sputtering powers. CGC films were able to sustain their electrical conductivity at strains above 100%. Instead of ultimate electrical discontinuity by channel crack propagation, CGC films maintained their conductivity by forming ligament structures, or a ‘conductive net,’ through trapped micro-cracks. XRD, AFM and in situ SEM analysis were used to investigate these stretchable conductors.

10.1038/srep13791

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Citations (11)

Plant cell-like tip-growing polymer precipitate with structurally embedded multistimuli sensing ability

Proceedings of the National Academy of Sciences (2023)

Chan Jin Park Jonghyun Ha Hae-Ryung Lee Keunhwan Park Jeong‐Yun Sun

Soft systems that respond to external stimuli, such as heat, magnetic field, and light, find applications in a range of fields including soft robotics, energy harvesting, and biomedicine. However, most of the existing systems exhibit nondirectional, nastic movement as they can neither grow nor sense the direction of stimuli. In this regard, artificial systems are outperformed by organisms capable of directional growth in response to the sense of stimuli or tropic growth. Inspired by tropic growth schemes of plant cells and fungal hyphae, here we report an artificial multistimuli-responsive tropic tip-growing system based on nonsolvent-induced phase separation of polymer solution, where polymer precipitates as its solvent dissolves into surrounding nonsolvent. We provide a theoretical framework to predict the size and velocity of growing precipitates and demonstrate its capability of sensing the directions of gravity, mechanical contact, and light and adjusting its growing direction in response. Exploiting the embedded physical intelligence of sensing and responding to external stimuli, our soft material system achieves multiple tasks including printing 3D structures in a confined space, bypassing mechanical obstacles, and shielded transport of liquids within water.

Soft Robotics

10.1073/pnas.2211416120

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Citations (2)