When this device gets jammed it must be a sorry sight. Technology Review reports on a machine that prints sheets of living tissue, using skin cells as “ink”:
The system, which lays down cells with the same fluid-based inkjet technology used in many printers, could print large swathes of living tissue directly onto the injuries of soldiers wounded on the battlefield. Covering burns and related wounds is of critical importance because, the scientists note, “any loss of full-thickness skin of more than 4 cm in diameter will not heal by itself.”
Tests on mice revealed advanced healing by both the second and third week of recovery, with complete closure and formation of scar tissue by week three in treated (but not untreated) subjects. The printer has two heads, one of which ejects skin cells mixed with fibrinogen (a blood coagulant) and type I collagen (the main component of the connective tissue in scars). The other head ejects thrombin (another coagulant).
Like the components of quick-setting resins which must be kept separate until mixing causes a chemical reaction that hardens the resin, the products of the two print heads mix to immediately form fibrin, yet a third protein involved in the clotting of blood. The whole confection is topped by a layer of keratinocytes (i.e. skin cells), which are also printed.