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[세미나: 8월 6일(화), 오후 1시 30분] Prof. Junsoo Kim, Northwestern University 

Title

Fracture-resistant soft materials by network topology engineering

Speaker

Prof. Junsoo Kim, Assistant professor in Mechanical Engineering at Northwestern University 

* Education

-  Sep. 2017 - May. 2022 Ph.D. in Materials Science & Mechanical Engineering, Harvard University

• Thesis Title: Fracture of Highly Entangled Polymer Networks

• Advisor: Prof. Zhigang Suo 

- Sep. 2011 - Aug. 2013 M.S. in Mechanical & Aerospace Engineering, Seoul National University

• Thesis Title: Probing the role of self-wettability in a deformable polymeric membrane 

with multiscale apertures

• Advisor: Prof. Kahp-Yang Suh

- Mar. 2007 - Feb. 2011 B.S. in Mechanical and Aerospace Engineering, emphasis in Acoustics (Cum laude), Seoul National University

* Professional Experience

- Jul. 2023 – present Assistant professor in Mechanical Engineering, Northwestern University

- Jun. 2022 – Jun. 2023 Postdoctoral researcher in Materials Science & Mechanical Engineering, Harvard University 

* Principal Investigator: Prof. Zhigang Suo 

- Sep. 2017 - May. 2022 Ph.D. candidate in Materials Science & Mechanical Engineering, Harvard University

* Advisor: Prof. Zhigang Suo

- Mar. 2014 - Aug. 2017 Researcher, Electronics and Telecommunications Research Institute

* Principal Investigator: Dr. Seung Eon Moon

- Sep. 2013 - Feb. 2014 Researcher, Global Frontier Center for Multiscale Energy System at Seoul National University

* Principal Investigator: Prof. Mansoo Choi

- Sep. 2011 - Aug. 2013 M.S. Candidate in Department of Mechanical Engineering, Seoul National University 

* Advisor: Prof. Kahp-Yang Suh

| Date | Tuesday, August 6th , 2024

| Time | 13:30 ~ 

| Venue | 33동 125호(WCU 다목적실)

[Abstract]

Soft materials, also called elastomers and gels, are used in high-volume applications such as tires as well as in emerging biomedical devices. However, they break easily. The waste tires and their debris pollute the environment, and the low fracture resistance of soft materials makes their use in biomedical applications impractical. In this talk, I will discuss how the network topology of polymer networks affects fracture properties such as toughness and fatigue resistance. We have shown that entanglements stiffen the polymer network but do not embrittle it [1]. Consequently, a polymer network in which entanglements outnumber crosslinks achieves both high modulus and toughness, overcoming long-standing modulus-toughness conflict. This principle is based on the network structure, not chemistry, so it can be applied to various material systems and fabrication processes.[2] Also, we have shown that the fatigue threshold of rubbers can be greatly improved by deconcentrating the stress at the crack tip by designing the molecular structure of filled rubbers [3]. The measured fatigue threshold is about 1,000 J/m2, which is a significant improvement given that it has been about 100 J/m2 since the first measurement in the 1960s.

[1] J. Kim*, G. Zhang*, M. Shi, Z. Suo†, “Fracture, fatigue, and friction of polymers in which entanglements greatly outnumber cross-links", Science, 374(6564), 212-216 (2021)

[2] G. Nian*, J. Kim*, X. Bao, Z. Suo†, “Making Highly Elastic and Tough Hydrogels from Doughs", Advanced Materials, 34(50), 2206577 (2022)

[3] J. Steck*, J. Kim*, Y. Kutsovsky†, Z. Suo†, “Multiscale stress deconcentration amplifies fatigue resistance of rubber", Nature, 624, 303-308 (2023)

| Host | 선정윤 교수(02-880-1714)