Biodegradable and Flexible Wood-Gelatin Composites for Soft Actuating Systems

Compliant materials
are indispensable for
many emerging soft robotics
applications. Hence, concerns regarding sustainability and end-of-life
options for these materials are growing, given that they are predominantly
petroleum-based and non-recyclable. Despite efforts to explore alternative
bio-derived soft materials like gelatin, they frequently fall short
in delivering the mechanical performance required for soft actuating
systems. To address this issue, we reinforced a compliant and transparent
gelatin-glycerol matrix with structure-retained delignified wood,
resulting in a flexible and entirely biobased composite (DW-flex).
This DW-flex composite exhibits highly anisotropic mechanical behavior,
possessing higher strength and stiffness in the fiber direction and
high deformability perpendicular to it. Implementing a distinct anisotropy
in otherwise isotropic soft materials unlocks new possibilities for
more complex movement patterns. To demonstrate the capability and
potential of DW-flex, we built and modeled a fin ray-inspired gripper
finger, which deforms based on a twist-bending-coupled motion that
is tailorable by adjusting the fiber direction. Moreover, we designed
a demonstrator for a proof-of-concept suitable for gripping a soft
object with a complex shape, i.e., a strawberry. We show that this
composite is entirely biodegradable in soil, enabling more sustainable
approaches for soft actuators in robotics applications.