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Shape reprogramming of 3D printed ionogels by solvent exchange with deep eutectic solvents

Polymer Journal volume 55, pages 1211–1223 (2023)Cite this article

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Abstract

Extrusion-based 3D printing, such as direct ink writing (DIW), is an emerging technique used to fabricate soft materials for advanced applications. For example, ionogels with sufficient stretchabilities and long-term stabilities have been printed for use as wearable sensors to monitor human activities. However, DIW printing of geometrically complex structures is challenging without supporting materials. Additionally, most ionogels exhibit insufficient mechanical toughness. We present a simple strategy with which to prepare 3D printable and tough ionogels that can be adjusted to any topography. The ink for 3D printing is a dispersion of cellulose nanocrystals (CNCs) in an aqueous solution of polyvinyl alcohol (PVA). After printing, the ink underwent a freeze‒thaw process to form soft but stretchable hydrogels via crystallization of the PVA. Hydrogels with planar geometries were then reconfigured into the desired 3D shapes. Finally, the water in the hydrogels was replaced by a deep eutectic solvent (DES) composed of choline chloride (ChCl) and glycerol. The solvent exchange process induced PVA crystallization to form ionogels with higher mechanical toughnesses than common hydrogels. We then implemented this simple method to prepare wearable sensors that adapted to the irregular surfaces of human bodies. This work provides a shape-reprogramming strategy for expanding the design space of wearable sensors.

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Acknowledgements

We thank the National Science and Technology Council in Taiwan for financial support (109-2636-E-006-005, 110-2222-E-006-009-MY3, and 111-2314-B-006-046). We also appreciate the support of the Higher Education Sprout Project, Ministry of Education to the Headquarters of University Advancement at National Cheng Kung University (NCKU).

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  1. These authors contributed equally: Hung-Yue Tsai, Hao-Jing Hsu

Authors and Affiliations

  1. Department of Chemical Engineering, National Cheng Kung University, Tainan, 70101, Taiwan

    Hung-Yue Tsai, Hao-Jing Hsu & Sheng-Sheng Yu

  2. Core Facility Center, National Cheng Kung University, Tainan, 70101, Taiwan

    Sheng-Sheng Yu

  3. Program on Smart and Sustainable Manufacturing, Academy of Innovative Semiconductor and Sustainable Manufacturing, National Cheng Kung University, Tainan, 70101, Taiwan

    Sheng-Sheng Yu

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  1. Hung-Yue Tsai
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Tsai, HY., Hsu, HJ. & Yu, SS. Shape reprogramming of 3D printed ionogels by solvent exchange with deep eutectic solvents. Polym J 55, 1211–1223 (2023). https://doi.org/10.1038/s41428-023-00814-4

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