Investigation of Tip Extrusion as an Additive Manufacturing Strategy for Growing Robots.

This paper presents a new design for material extrusion as embeddable additive manufacturing technology for growing robots inspired by plant roots. The conceptual design is proposed and based on the deposition of thermoplastic material a complete layer at a time. To guide the design of the system, we first studied the thermal properties through approximated models considering PLA (poly-lactic acid) as feeding material. The final shape and constituent materials are then accordingly selected. We obtained a simple design that allows miniaturization and a fast assembly of the system, and we demonstrate the feasibility of the design by testing the assembled system. We also show the accuracy of our thermal prediction by comparing the thermal distribution obtained from FEM simulations with experimental data, obtaining a maximal error of similar to 8 degrees C. Preliminary experimental growth results are encouraging regarding the potentialities of this approach that can potentially achieve 0.15 divided by 0.30 mm/s of growth speed. Our results suggest that this strategy can be explored and exploited for enabling the growth from the tip of artificial systems enouncing robots' plasticity.