Fig. 1

3D Printing Biological Machines. a Schematic of 3D printing apparatus used to fabricate bio-bot skeletons using a biocompatible polymer. b Image of 3D printed bio-bot coupled to tissue engineered skeletal muscle. c Electrical and optical signals are used to drive contraction of the tissue engineered muscle, with each contraction corresponding to a “step” forward. External signals can thus be used to control bio-bots to walk on 2D substrates. The direction of walking can be dictated by either the geometry of the skeleton or the region of muscle stimulated. d Future work on bio-bots could involve incorporating multiple tissue types (such as muscle, vasculature, neurons) to create robots that can sense, process, and respond to dynamic environmental signals in real-time. Shown in this schematic is a bio-bot that senses a harmful chemical gradient, walks toward it, and secretes biological factors to neutralize the toxin. This is just one of many potential applications for bio-bots in future