Figure 4. Structures fabricated via the inverted deposition configuration. (a) A bio-inspired “beehive.” (b) Conical structure with large overhangs and small base fabricated with zero support material. (c) Twisted conical structure. (d) Load bearing arch. (e) Fully cured inverted arch supporting a 1 kg weight.
Alternatively, this printing technique can be configured to fabricate structures horizontally, effectively enabling production of 90⁰ overhangs with zero support material (Figure 5a). By reorienting the extrusion nozzle, the zero-support horizontal beams could be fabricated such that layers are deposited parallel to the build plate similar to conventional DIW printing. The rapid photopolymerization affords rigidity to the structure, allowing it to resist the increasing bending moment imparted by the cumulative weight of the horizontal beam. To further demonstrate the capabilities of these unstructured/alternative build orientations, we deposited conductive ink paths on the surface of a horizontally printed beam to create a functional 3D printed structure to sense deflection (Figure 5b, Video 3). The results of normalized resistance over time for the 50 mm horizontal beam sensor subjected to cyclic deflection three times at δ = 0.4, 0.8, and 1.2, 1.6, and 2.0 mm are presented in Figure 5c.