Three-dimensional soft structures are difficult to fabricate without any supporting materials in additive manufacturing due to their extremely low stiffness against gravity. This study presents the feasibility of a conceptual 3D printing method that enables a hydrostatic condition and eventually achieves support-free fabrication, named hydrostatic 3D printing (H3P). Hydrostatic 3D printing utilizes low one-photon polymerization (LOPP) to realize polymerization under the polymer resin surface, as opposed to surface polymerization in stereolithography (SLA). The cured part inside of the resin is then automatically supported by the hydrostatic pressure. A preliminary study was designed to observe LOPP of a UV curable silicone material at a wavelength of 365 nm. A single-spot curing and a continuous printing were both investigated under different light intensities and exposure times. The equivalent exposure time for LOPP in a continuous printing was found to be much shorter than a stationary single-spot curing due to a non-linear intensity distribution. Initial results have demonstrated the feasibility of hydrostatic printing using LOPP while also revealing the challenges of hydrostatic 3D printing.
