3D printing of mechanically tough and self-healing hydrogels with carbon nanotube fillers

Soo A Kim; Yeontaek Lee; Kijun Park; Jae Park; Soohwan An; Jinseok Oh; Minkyong Kang; Yurim Lee; Yejin Jo; Seung-Woo Cho; Jungmok Seo

doi:10.18063/ijb.765

3D printing of mechanically tough and self-healing hydrogels with carbon nanotube fillers

Int J Bioprint. 2023 May 31;9(5):765. doi: 10.18063/ijb.765. eCollection 2023.

Authors

Soo A Kim¹, Yeontaek Lee¹, Kijun Park¹, Jae Park^{1

2}, Soohwan An³, Jinseok Oh¹, Minkyong Kang¹, Yurim Lee¹, Yejin Jo¹, Seung-Woo Cho³, Jungmok Seo^{1

2}

Affiliations

¹ School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea.
² LYNK Solutec Inc., Seoul 03722, Republic of Korea.
³ Department of Biotechnology, Yonsei University, Seoul 03722, Republic of Korea.

Abstract

Hydrogels have the potential to play a crucial role in bioelectronics, as they share many properties with human tissues. However, to effectively bridge the gap between electronics and biological systems, hydrogels must possess multiple functionalities, including toughness, stretchability, self-healing ability, three-dimensional (3D) printability, and electrical conductivity. Fabricating such tough and self-healing materials has been reported, but it still remains a challenge to fulfill all of those features, and in particular, 3D printing of hydrogel is in the early stage of the research. In this paper, we present a 3D printable, tough, and self-healing multi-functional hydrogel in one platform made from a blend of poly(vinyl alcohol) (PVA), tannic acid (TA), and poly(acrylic acid) (PAA) hydrogel ink (PVA/TA/PAA hydrogel ink). Based on a reversible hydrogen-bond (H-bond)-based double network, the developed 3D printable hydrogel ink showed excellent printability via shear-thinning behavior, allowing high printing resolution (~100 μm) and successful fabrication of 3D-printed structure by layer-by-layer printing. Moreover, the PVA/TA/PAA hydrogel ink exhibited high toughness (tensile loading of up to ~45.6 kPa), stretchability (elongation of approximately 650%), tissue-like Young's modulus (~15 kPa), and self-healing ability within 5 min. Furthermore, carbon nanotube (CNT) fillers were successfully added to enhance the electrical conductivity of the hydrogel. We confirmed the practicality of the hydrogel inks for bioelectronics by demonstrating biocompatibility, tissue adhesiveness, and strain sensing ability through PVA/TA/PAA/CNT hydrogel ink.

Keywords: 3D Printing; Bioelectronics; Hydrogels; Nanofillers; Self-healing; Toughness.