Ordinarily, commonly used fused deposition modelling (FDM)-type printers create items by extruding successive layers of molten plastic. Once the layers of deposited plastic have cooled and fused together, they form a hardened solid object.
Sometimes, though – due to a flaw in the printer or the programming – not enough plastic is extruded. This is known as under-extrusion, and it results in the finished product being full of small gaps.
MIT Media Lab grad student Jack Forman decided to put that error to use, creating a program that causes off-the-shelf, inexpensive FDM printers to under-extrude in a precise and controlled "glob-stretch" pattern – the latter is made up of tiny polymer plastic pillars linked together by thin polymer strands.