Programmable cellulose nanocomposite for 4D printing of bioinspired robotic matter

Abstract

This interdisciplinary research combines materials science, bioinspired design, and additive manufacturing to develop programmable and printable nanocellulose-based composites with the potential to shape-morphing in response to changes in humidity and temperature. In this project, thermoresponsive double-network hydrogel inks of poly(N-isopropylacrylamide) (PNIPAM) and sodium alginate, reinforced with cellulose nanocrystals (CNC) and nanofibers (CNF) will be synthesised for prototyping, via 3D/4D printing, robotic matter bioinspired in plant movements. The incorporation of CNC and CNF increases the mechanical strength and stiffness of hydrogel matrices, optimizes the control of rheological properties, and enables the modelling of mechanical and structural characteristics, due to the anisotropic and hygroscopic nature of nanocellulose. Moreover, the alignment of the nanocelluloses during extrusion printing dictates the swelling direction of the hydrogels, allowing the control of shape transformations. This possibility to program the behaviour of the structures after the printing process opens doors for applications in 4D printing of actuators and autonomous soft robots. To date, most of the soft robots are dependent on pneumatic and electric forces, which limit their autonomy and range of applications. In this sense, this project aims to contribute to the innovative area of robotic matter, which comprehends the use of responsive materials and the design of adaptable structures, through the development of nanocomposites with embodied intelligence. Therefore, it is expected that the results obtained will expand the knowledge about the use of nanocellulose-based inks as robotic matter for a new generation of autonomous and sustainable soft robots.