A preliminary study of a robotic probe for soil exploration inspired by plant root apexes

Plants are organisms characterized by an aerial part and a root system. Plants have developed directional growth responses to deal with the copious and rapid changes in their environment in order to compensate for their sessile nature. The process by which plant roots expand in soil involves water uptake through osmosis and imbibition, and an overall increase in size by cell division. Each root tip (apex) has sensors to get information from the environment, which is then transduced, processed, and used to direct the growth towards regions of the soil with the best minerals and water availability. This knowledge has inspired a novel concept of robotic system, leading to a first mechanical design and prototype of a steering tip inspired by plant apexes, based on a new actuation biologically inspired osmotic principle. A parametric model of the system geometry has been developed and presented here, in order to obtain an optimal size of the robotic system and to achieve the best compromise between steering performance and actuation times. First prototypes of the robotic apex have been fabricated by a 3D printer InVision si2, with a plastic material, including osmotic actuators, gravity and humidity sensors, and the electronics for sensory data acquisition and steering control.