3D printing resin enables simultaneous printing of solid and dissolvable objects

Elaborate multipart objects, like this chain, can be 3D printed all at once using a new vat polymerization technique. Photo Credit: American Chemical Society

One-pot recipes – which are meals made entirely in one cooking vessel, start to finish – make preparing meals quick and easy. Researchers in California have developed an approach they say can do the same for additive manufacturing.

Supported in part by funding from the U.S. Department of Energy, the research team – composed of scientists with University of California Santa Barbara and Lawrence Livermore National Laboratory, in Livermore, Calif. – have demonstrated a new resin that simultaneously creates solid objects and dissolvable structural supports, depending on what type of light the resin is exposed to. The approach could increase the applications for 3D-printed objects, including tissue engineering scaffolds, joints, and hinges.

The problem the team tried to solve centres around vat polymerization, which is a 3D printing process that uses a vat or container of liquid photopolymer resin and selectively cures it with light, layer by layer, to build a 3D object. This 3D printing method is typically fast and inexpensive but it has downsides, including the fact that intricate items created with vat polymerization usually require supports such as temporary scaffolds, which get attached when the original object is dipped into a second batch of resin; and this second step adds time and expense to the process because of the extra resin and extra effort required to remove the temporary supports.

The California researchers have developed a one-pot method of vat polymerization by formulating a single resin that hardens into permanent and dissolvable materials when exposed to ultraviolet (UV) and visible light, respectively. They also created a special 3D printer that emits both types of light, allowing the researchers to print an object and its supports simultaneously.

The researchers mixed different components, including acrylate/methacrylate and epoxy monomers, as well as photoreactive substances that absorb both visible and UV light, to create their one-pot resin. During initial tests with the photoreactive substance, they observed that under visible light the acrylate monomers solidified and formed dissolvable, anhydride-based support materials. Under UV light, but not visible light, the epoxy monomers hardened into the permanent portion of the object.

To dissolve the support material, the researchers added the objects to a sodium hydroxide solution at room temperature, and the permanent object was revealed within 15 minutes. Importantly, the researchers note that the anhydride-based scaffolds degraded into nontoxic compounds.

In subsequent demonstrations of the new approach, the team created increasingly complex structures: a checkerboard pattern, a cross, interlocking rings (pictured), a ball in a cage, and two balls in a helix. These objects would be challenging to fabricate with layer-based vat polymerization printing methods, the researchers noted, as they’re not structurally supported by previous layers. “We’ve demonstrated a base-degradable thermoset to pattern print supports in a one-pot formulation along with the primary structural material,” said team member Maxim Shusteff, a group leader at Lawrence Livermore National Laboratory. “This approach provides a robust method for the dual-wavelength patterning of sacrificial thermoset supports, broadening the range of accessible 3D printable materials and geometries.”