Embedded 3D Printing of Silicone for Soft Actuator with Stiffness Gradient and Programmable Workspace

Soft pneumatic actuators can accomplish various customizable deformation/motion through the distribution of cavities and gradients in stiffness. However, traditional manufacturing methods, say molding, struggle to produce soft actuators with both complex cavities and desirable stiffness distributions. Regular 3D printing methods usually need extra printheads for support materials to fabricate soft actuators with cavities. In addition, the printing quality and fidelity of the whole structure cannot be uniform due to the effect of gravity, especially for a soft actuator with overhang features. To fabricate a soft actuator of uniform fidelity but desirable stiffness distributions, we propose an embedded 3D printing approach with only one active mixing printhead. By adjusting the mixing ratio of the dual-component silicone, we can achieve designated stiffness gradients, ranging from 30.2 kPa to 198 kPa. With this approach, we successfully fabricate soft pneumatic actuators with overhang features, which exhibit programmable elongation and radial expansion. Additionally, we fabricate soft bending actuators which can achieve programmable workspaces due to their predetermined stiffness distribution.