Fig. 8: Functional single and multi-material prints.

a Cross section view of the designed pneu-net actuator in CAD. b Cross-sectional cut of the printed pneu-net actuator highlighting common building blocks used during fabrication such as bridges and thin walls. These soft, thin features begin to deform under gravity when the part is dissected though some shape distortion at the edges is the result of the extruder toolpath. c 3D printed silicone pneu-net design. Two of them attached into a housing and turned into a soft robotic gripper. Open position achieved at vacuum ∆P = −7.93 kPa. Normal stance position (d) ∆P = 0 kPa. Actuated position (e) ∆P = 10.5 kPa. f Soft robotic gripper lifting a cherry at ∆P = 21.4 kPa. g Multi-material 3D printed hand design. Palm is printed with silicone and fingers printed with foam material. Corresponding Shore hardnesses in 00 scale are 57 and 51. h Density control by changing print material. Cube on the left printed with only silicone material possessing ⍴ = 0.96 ± 0.03 g ml⁻¹ and cube on the right printed with only foam (10 wt%) material possessing ⍴ = 0.71 ± 0.05 g ml⁻¹. We used food grade anti wear hydraulic fluid as the medium. i Optical image of the foam region under microscope to highlight cell structures between layers. j Transition layer from foam to silicone after material change command. Small bubbles interfered the silicone layer, since the mixed material residency time is 25 s in the mixing chamber. k Silicone to silicone layer interface. l Time-lapse of the buoyancy control with a pre-programmed multi-material cube.