The study on pH gradient control in solution for driving bacteria

Medical applications are the most impactful areas of microrobotics, such as targeting tumoral lesions for therapeutic purposes, minimally invasive surgery (MIS) and highly localized drug delivery. However, miniaturization of the power source with an effective onboard controllable propulsion system has prevented the implementation of such mobile robots. Flagellated chemotactic bacteria can be used as an effective integrated propulsion system for microrobots. In this paper, we study the pH gradients control in solution for driving bacteria. The swimming property of flagellar bacteria and mechanism of forming the pH gradient field in solution are discussed. By experiments, we found that the pH gradient field distribution in solution is mainly related to the electrode shape. And the input voltage value can control the stable time of the pH gradient field, while it has no effect on the distribution of the field. The electric potential distribution is analyzed by simulation with COMSOL Multiphysics. The simulation results are consistent with the experiment results, which indicate that the bacteria movement can be controlled by the electrodes’ shape and the input voltage.