Liquid-in-liquid 3D printing was first presented in a BMW funded MIT project.

Although the project initially seemed limited in scope the possibilities of 3D printing within a liquid medium opens new opportunities in terms of escaping gravitational pull and thus producing parts that require a more volumetric approach, such as biological structures and organs. As reported by ScienceMag, liquid in liquid bioprinting is exactly what a team of researchers from a number of academic and research institutions in Shenzhen demonstrated in a paper titled “Freeform, Reconfigurable Embedded Printing of All-Aqueous 3D Architectures“.

Replicating complicated body parts and blood vessels is a major challenge. That’s because these vascularized tissues are hard to build up in traditional solid layer-by-layer 3D printing without constructing supporting scaffolding that can later prove impossible to remove.

One potential solution is thus replacing these support structures with liquid—a specially designed fluid matrix into which liquid designs could be injected before the “ink” is set and the matrix is drained away. But past attempts to make such aqueous structures have literally collapsed, as their surfaces shrink and their structures crumple into useless blobs.

Researchers from China turned to water-loving, or hydrophilic, liquid polymers that create a stable membrane where they meet, thanks to the attraction of their hydrogen bonds. The researchers say various polymer combinations could work; they used a polyethylene oxide matrix and an ink made of a long carbohydrate molecule called dextran. They pumped their ink into the matrix with an injection nozzle that can move through the liquid and even suck up and rewrite lines that have already been drawn. The resulting liquid structures can hold their shape for as long as 10 days before they begin to merge.

Using their new method, the researchers printed an assortment of complex shapes—including tornadoesque whirls, single and double helices (above), branched treelike shapes, and even one that resembles a goldfish. Once printing is finished, the shapes are set by adding polyvinyl alcohol to the inky portion of the structure. That means, the scientists say, that complex 3D printed tissues made by including living cells in the ink could soon be within our grasp.

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