Multi-Responsive 3D Printed Nanocellulose-Based Hydrogels Programmable in Space and Time

Stimuli-responsive materials are desirable for a variety of functional applications, that range from biomedical devices, sensors and actuators to adaptive surfaces and deployable structures. However, as the natural environment offers multiple stimuli at the same time, current solutions often lack multi-responsiveness and display poor control over their properties over time. Here, I will introduce a new multi-stimuli-responsive material platform, realized via additive manufacturing, that can be precisely programmable to morph both in space and time. In my talk, I will highlight the fabrication steps that led to the development of composite inks for Direct Ink Writing (DIW), formed by double-network hydrogel matrices, reinforced by a high content of cellulose nanofibers and nanocrystals. Thus, I will display how the alignment of the reinforcing particles, induced by intense shear forces during DIW, provides composites with a highly anisotropic microstructure, key to tune the stiffness as well as the swelling/shrinking behavior of printed actuators [1, 2]. Additionally, I will highlight how the reversible shape-morphing capability of bilayer systems, as well as their activity in time, as a fourth dimension, can be tailored through processing parameters and geometrical design [3], in response to multiple stimuli scenarios, such as simultaneous variations in humidity, temperature, pH, and ion concentration. Finally, I will show how the performance of multi-responsive hydrogels can be leveraged to design and fabricate, by additive manufacturing, mechanically versatile architectures and mechanical sensors with outputs structured through the Boolean logic and logic gates, paving the way to multi-logic stimuli-responsive materials.<br/><br/>References<br/>[1] Siqueira, G., Kokkinis, D., Libanori, R., Hausmann, M. K., Gladman, A. S., Neels, A., Tingaut, P., Zimmermann, T., Lewis, J. A., & Studart, A. R. (2017). Cellulose Nanocrystal Inks for 3D Printing of Textured Cellular Architectures. Advanced Functional Materials, 27(12). https://doi.org/10.1002/adfm.201604619<br/>[2] Champeau, M., Heinze, D. A., Viana, T. N., de Souza, E. R., Chinellato, A. C., & Titotto, S. (2020). 4D Printing of Hydrogels: A Review. Advanced Functional Materials 30(31). https://doi.org/10.1002/adfm.201910606<br/>[3] Kotikian, A., Mcmahan, C., Davidson, E. C., Muhammad, J. M., Weeks, R. D., Daraio, C., & Lewis, J. A. (2019). Untethered soft robotic matter with passive control of shape morphing and propulsion. Sci. Robot (4). https://doi.org/10.1126/scirobotics.aax7044