Controlling the Water Diffusion Inside Smart 4D-Printed HBC by Functional Channels

Abstract

Hydromorph Biocomposites (HBCs) are self-shaping materials whose motions are actuated by moisture-induced swelling of natural fibers and designed through a multilayered bioinspired material architecture. Their reactivity, i.e., kinetic of actuation, is relatively slow and is currently limited by the moisture transport. Porosities are commonly assumed to be a defect in composite materials that results in reduced mechanical performance. However, in biological structures porosities within the tissue architecture provide essential functions (lightness, moisture transport, and actuation). Inspired by biological mesostructures, a 3D-printing process is applied to precisely define the architecture of an HBC that incorporates functional porosities, i.e., channels. The purpose is to improve the moisture-induced actuation reactivity without compromising any other functional performance. First, 3D-printed wood fiber-reinforced biocomposites are designed with various channel content (from 0% to 10%), size (from 0.5 to 3.0 mm), and distribution patterns across the samples. Immersed in water, these novel HBCs with tailored channel structures fasten the water transport by triggering capillary transport. The presented results demonstrate that implementing functional channels in the mesostructure of 4D-printed HBC bilayers makes it possible to achieve an eight-fold improvement in the speed of shape-change transformation while enabling new capabilities to functionally tune the morphing performance of HBCs.