A study on plant root apex morphology as a model for soft robots moving in soil

Abstract

Plants use many strategies to move efficiently in soil, such as growth from the tip, tropic movements, and morphological changes. In this paper, we propose a method to translate morphological features of Zea mays roots into a new design of soft robots that will be able to move in soil. The method relies on image processing and curve fitting techniques to extract the profile of Z. mays primary root. We implemented an analytic translation of the root profile in a 3D model (CAD) to fabricate root-like probes by means of 3D printing technology. Then, we carried out a comparative analysis among the artificial root-like probe and probes with different tip shapes (cylindrical, conical, elliptical, and parabolic) and diameters (11, 9, 7, 5, and 3 mm). The results showed that the energy consumption and the penetration force of the bioinspired probe are better with respect to the other shapes for all the diameters of the developed probes. For 100 mm of penetration depth and 7 mm of probe diameter, the energy consumption of the bioinspired probe is 89% lesser with respect to the cylindrical probe and 26% lesser with respect to the conical probe. The penetration performance of the considered tip shapes was evaluated also by means of numerical simulations, obtaining a good agreement with the experimental results. Additional investigations on plant root morphology, movement strategies, and material properties can allow the development of innovative bioinspired solutions exploitable in challenging environments. This research can bring to breakthrough scenarios in different fields, such as exploration tasks, environmental monitoring, geotechnical studies, and medical applications.

Tissue growth constrains root organ outlines into an isometrically scalable shape

“…Three-dimensional root tip shapes have been previously shown to affect the penetration ability of roots into soil in wheat ( Colombi et al, 2017 ), or into a hard medium in Arabidopsis ( Roue et al, 2020 ). In addition, an engineering approach using soft robots suggested that plant root tip morphology governs the penetration stress and the efficient elongation in soil ( Mishra et al, 2018 ). Our simulations indicated that the mechanical force produced by the tissue growth was uniformly distributed on the surface of the catenary-curved root tips ( Fig.…”

Down to the root of vegetated soil: challenges and state-of-the-art

“…The stress transfer and pore water distribution, however, are nearly impossible to obtain experimentally. Meanwhile, there is an increasing need to fundamentally understand how roots grow, displace, and stabilize between soil particles, largely motivated by a growing interest in bio-inspired robotics [55,56]. With particle-scale modeling techniques, such as the discrete element method (DEM), mechanical interactions between particles and root branches can be simulated explicitly.…”

Organismal Design and Biomimetics: A Problem of Scale

“…Further developments led to PLANTOIDS, robotic systems inspired by plant roots for soil exploration and monitoring [128]. In this field, other examples are works by Tonazzini et al [130] nd Mishra et al [131] for the study and development of robotic probes with root-like morphologies able to better accomplish penetration tasks. In particular, the latter working group developed an artificial root-like shaped probe inspired by Zea mays roots using 3D printing technology, which is more efficient in terms of penetration force and energy consumption compared to standard shape probes [131].…”