Researchers develop 3D printed creative ice structures, including an octopus

Researchers at Carnegie Mellon University (CMU), a private research institute in Pennsylvania, have developed a method for 3D printing tiny artistic ice structures. The high-speed, reproducible fabrication method turns the 3D printing process "inside out," according to an article published on the university's official website.

"Using our 3D ice process, we can fabricate microscale ice templates with smooth walls and branched structures with smooth transitions," said Akash Garg, co-author of the study, a mechanical engineering Ph.D. scholar at the university. "These can subsequently be used to fabricate microscale parts with well-defined internal voids."

Garg and Saigopalakrishna Yerneni, a postdoctoral associate in chemical engineering at CMU, collaborated on the study.

Water is considered an excellent choice for bioengineering applications because it is the most abundant substance on the planet's surface and the primary building block of all living organisms. Water's simple and rapid phase transition to ice opens up exciting possibilities for using it as an environmentally friendly structural material.

"It doesn't get any more biocompatible than water," said Garg.

How does it work?

The printed ice structures are used as sacrificial templates for "reverse molding" or inside-out 3D printing. The ice structures are immersed in a chilled structural material, such as resin, in liquid or gel form.

The water is removed after the material has been set or cured. The ice can be melted to evacuate the water for this purpose. Alternatively, ice can be sublimated by converting it to water vapor rather than liquid water. Because the ice can be easily sublimated, it can be removed easily after casting and solidifying the surrounding structural material.

A high-resolution 3D printing system is used to deposit water droplets onto a temperature-controlled platform at -35 C, which rapidly converts the water to ice.

The new process allows printing branched geometries with smooth surfaces and continuous variations in diameter with smooth transitions by modulating the ejection frequency of the water droplets and synchronizing it with stage movements.

The researchers demonstrated this by printing a tree, a helix around a pole, and even a one-and-a-half-millimeter tall octopus figurine out of ice. Because of the water's rapid phase change and the ice's strength, freeform 3D printing of ice structures was possible without the need for time-consuming layer-by-layer printing or support structures.

"Controlling so many parameters was challenging," explained Garg. "We gradually built up in complexity."

'Amazing accomplishment'

Experiments were carried out to determine the printing path, motion-stage speed, and droplet frequencies required to fabricate smooth ice structures with straight, inclined, branching, and hierarchical geometries in a reproducible manner.

Burak Ozdoganlar, the associate director of the Engineering Research Accelerator at CMU, who oversaw the study, called it "an amazing accomplishment that will bring exciting advances."

"We believe this approach has enormous potential to revolutionize tissue engineering and other fields, where miniature structures with complex channels are demanded, such as for microfluidics and soft-robotics."

In as little as a year, the 3D ice process could be used for engineering applications such as creating pneumatic channels for soft robotics. However, clinical application for tissue engineering will take longer.

The study was first published in Advanced Science.

Abstract:

Water is one of the most important elements for life on earth. Water's rapid phase-change ability along with its environmental and biological compatibility also makes it a unique structural material for 3D printing of ice structures reproducibly and accurately. This work introduces the freeform 3D ice printing (3D-ICE) process for high-speed and reproducible fabrication of ice structures with micro-scale resolution. Drop-on-demand deposition of water onto a −35 °C platform rapidly transforms water into ice. The dimension and geometry of the structures are critically controlled by droplet ejection frequency modulation and stage motions. The freeform approach obviates layer-by-layer construction and support structures, even for overhang geometries. Complex and overhang geometries, branched hierarchical structures with smooth transitions, circular cross-sections, smooth surfaces, and micro-scale features (as small as 50 µm) are demonstrated. As a sample application, the ice templates are used as sacrificial geometries to produce resin parts with well-defined internal features. This approach could bring exciting opportunities for microfluidics, biomedical devices, soft electronics, and art.