Plant Mobile Robot Using <i>Mimosa pudica</i>

Abstract

Plants respond physically to external stimuli (such as light and electricity), and these stimuli-responsive physical behaviors facilitate plants being used as actuators for robotic systems. However, achieving robot mobility through plants remains challenging. Moreover, there is a lack of quantitative knowledge of the actuation characteristics of plants. In this study, to achieve the mobility of robots by plants, we employed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Mimosa pudica</i> as the target plant and investigated its actuation characteristics. Specifically, we focused on a specific part of the plant called the pinnule, which is a small leaf that exhibits the motions of closing and opening. The experimental results revealed that the average closing and opening times over the tested voltage were 4.5 s and 798 s, respectively. The measured force of the pinnule was up to 0.19 mN, which corresponded to a power density of 0.16 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> W/kg. We then designed and fabricated a mobile robot that could locomote on the water surface by exploiting the rowing movement of the pinnules. The experimental results indicated that the robot (mass 0.5 g) was able to move on the water surface in response to the voltage input, exhibiting speeds of up to 3.3 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> μm/s and a thrust force of up to 52.3 μN. These values were in good agreement with the model predictions. The results of this study further promote the integration of plants into robots, advancing the development of sustainable, environmentally friendly robotics.