Associate Professor, School of Mechanical & Aerospace Engineering, Nanyang Technological University, Singapore

Biography: Dr. Lin Li received his PhD degree in Polymer Science in 1989 from Kyoto University, Japan. During the period from 1989 to 1999, he worked as a R&D scientist, research fellow, and senior scientist at several industrial and academic laboratories in Japan and Canada. He did his postdoctoral research in the group of Professor Mitchell A Winnik in Department of Chemistry, University of Toronto, Canada. In August 1999, he joined as Associate Professor at the School of Mechanical & Aerospace Engineering, Nanyang Technological University, Singapore. His recent research interests and activities include (i) synthesis of nanocarriers for drug & gene delivery, (ii) development of advanced polymer nanocomposites, (iii) rheological studies of polymer gels and hydrogels, (iv) 3D printing with hydrogels, (v) 4D printing with smart materials, etc. To date, he has authored and co-authored 205 journal papers. His journal papers have garnered more than 7,000 citations (Web of Science) with a Hirsch-index of 46 (Web of Science).

Speech Title: Synthesis of A Highly Stretchable and Self-healing Double Network Hydrogel

Aims: We aim to develop highly stretchable and self-healing double betwork (DN) hydrogels for special applications.

Methods: We used a polysaccharide, κ-carrageenan, to make a physical and thermoreversible network to synthesize a κ-carrageenan/PAAm DN hydrogel by means of one-pot method.

Results: We have synthesized a stretchable DN hydrogel with excellent recoverable, self-healing and 3D printable properties by combining an ionically crosslinked κ-carrageenan network with a covalently crosslinked PAAm network. Because of thermoreversible feature of the sol-gel transition of the κ-carrageenan, the stiffness and toughness of the DN hydrogel even with a notch could be respectively recovered to 91 % and 84 % by heating at 90 oC for 20 min. The thermoreversible sol-gel transition is also responsible for the self-healing property of the DN hydrogel, where the cut surfaces could be healed via the gel-sol-gel transition in a heating-cooling cycle, and the self-healed DN hydrogel exhibited a high self-healing efficiency (99.2% in conductivity). More importantly, the warm pre-gel solution of κ-carrageenan/AAm was sucessfully used as an ink of a 3D printer to print the hydrogel into complex 3D structures, and the printed DN hydrogel samples demonstrated the high mechanical strength after UV-exposure. Furthermore, the κ-carrageenan/PAAm DN hydrogel possesses a strain sensitivity, which endows our DN hydrogel to be used as wearable strain sensor to effectively monitor and distinguish multifarious motions of a human body.

Conclusions: This study has for the first time demonstrated that the κ-carrageenan/PAAm DN hydrogel is not only stretchable and recoverable, but also self-healing, 3D-printable and strain-sensitive.