Tunable Silicone/Epoxy Hybrid Resins for the Fabrication of Functionally Graded Materials Applied to Flying Devices

The multi-material structures found in soft robot bodies, from stretchable elastomers to hard connectors, can display highly distinct physicochemical properties, challenging the engineering of robust interfaces required for long-term performance in real-world scenarios. A novel family of hybrid resins combining platinum-catalyzed silicones with epoxy resins cured by acid anhydrides was recently reported ^[1]. These hybrids enabled the additive manufacturing of functional multi-material bodies exhibiting five orders of magnitude of elasticity (from 20 kPa to ~2 GPa) with strong interfaces (from 1 to 3 kJ m^-2), by adjusting the composition of the hybrid resins. The excellent control of ink rheological behavior via nanoclay addition allowed for direct-ink-writing, enabling seamless control of topology and mechanical properties with sub-millimeter resolution in three dimensions.<br/>In this work, the significance of this new class of hybrids is further demonstrated via the fabrication of membranes for flying devices. Two types of devices were manufactured: (i) a bird-inspired folding wing made of an elastic membrane with anisotropic deformation bonded on a 3D-printed bone structure made in PLA; (ii) an insect-inspired flapping wing for micro-air vehicles. For the first device, the formulation of the hybrids was modified through the addition of cellulose-based fillers to increase the interfacial toughness between the hybrids and PLA. In the second case, adjustments in the fabrication strategy were made to successfully manufacture light-weight thin wings (&lt;50 μm).<br/><br/>[1] V. S. Joseph, T. Calais, T. Stalin, S. Jain, N. K. Thanigaivel, N. D. Sanandiya, P. Valdivia y Alvarado, <i>Applied Materials Today</i> <b>2021</b>, <i>22</i>, 100979.