Shimmery, biodegradable inks in a rainbow of hues can be squeezed from a syringe to form multicoloured sculptures — without the heating usually required for 3D printing.

Three-dimensional printing techniques have opened a world of opportunities for artistic expression, but most such methods use plastic ‘inks’ that can soften when heated during printing. Anne Arnold and her colleagues at the Pacific Northwest National Laboratory in Richland, Washington, refined a heat-free alternative using low-cost polymers purified from brown seaweed.

The team dissolved the algal polymers in water to form viscous liquids, which are then combined with a solution of calcium chloride. The positively charged calcium ions join together the negatively charged portions of various polymer strands, linking the polymers and turning the liquid inks into pliable gels that hold their shapes.

Pigments made of the mineral mica conferred lustrous colours to the colourless inks. Using a handheld syringe, the researchers ‘printed’ a 2D figure of a firefly and a 3D model of a brain.

A final application of calcium chloride solution maximized a printed piece’s longevity. But over time, the alga-based polymers will biodegrade, preventing discarded art from accumulating.