3D printing has become one of the most promising methods to construct delicate 3D structures, especially with the development of the continuous 3D printing and the volumetric 3D printing. We have previously proposed a continuous DLP 3D printing strategy by employing a curing interface to reduce the adhesion between the cured resin and the curing interface, (Research, 2018, 2018, 479560). The designing of the curing interface is inspired by the slippery property of the pitcher plant's peristome surface. In addition to the low adhesion, resin refilling velocity is also high, where the strategy is not limited by the types of resins, even with high viscosity. From resin mixed with immiscible salt particles, where the viscosity is significantly increased, continuous 3D printing can also be conducted to prepare delicate structures, for example, the conical structure with arrays of micro-cavities along the sidewall (Nature Communicatons, 2020, 11, 521). Although effective in constructing fine structures, compared with fused deposition modeling (FDM) or 3D extruding-based printing, most UV-curing based 3D printing methods has low wet material utilization efficiencies. During the continuous 3D printing process, liquid resin inevitably adheres to the surface of the cured structure, whose amount will increase with the printing speed and viscosity. In addition, current UV projectors are LED-based, the “dark” region, i.e., the non-patterned region of a projected slice, is not really 100% “black” or 0 UV intensity. With the increase of the employed UV intensity, the afterglow of the “dark” region also becomes brighter and brighter, which may induce the UV curing of the non-patterned region. Accompanying with the residual resin on the cured structure surface, and the continuous irradiation of the resin under exciting light including the afterglow of the UV projector, extra curing or printing instability occurs which will decrease the 3D printing resolution.
Here, we propose a one-droplet 3D printing strategy to fabricate controllable 3D structures from a single droplet ascribing to the receding property of the three-phase contact line (TCL) of the resin droplet. The well-controlled dewetting force of liquid resin on the cured structure results in the minimization of liquid residue and the high wet and net material utilization efficiency in forming a droplet into a 3D structure. Besides, extra curing induced protruding or stepped sidewalls under high printing speed, which requires high UV intensity can be prevented. The critical is the free contact surface property of the droplet system with the introduction of the receding TCL, which increased the inner droplet liquid circulation and reduces the adhesion properties among the liquid resin, cured resin, and resin vat.
For more details, check out our paper recently published in Nature Communications:
Continuous 3D printing from one single droplet
Nature Communications, 2020, 11, 4685