Design and Numerical Modeling of an On-Board Chemical Release Module for Motion Control of Bacteria-Propelled Swimming Micro-Robots

On/off motion control of bacteria-propelled synthetic bodies was previously achieved using a chemical switching technique. A chemical agent (CuSO₄) directly binds to the rotor of the flagellar motor inhibiting it. When desired, a second chemical agent (EDTA) is introduced, which binds to the CuSO₄ molecules, freeing the motor and allowing the bacteria to resume its motion [1]. To facilitate localized delivery of the control agents and reduce the diffusion time, we propose an on-board chemical release scheme for the first time. The proposed microfluidic motion control module contains two sets of optomechanically responsive nanocomposite paraffin wax micro-valves which can be independently actuated. To demonstrate the feasibility of the concept, a transient two-dimensional mass transfer numerical model is developed and the transient concentration profiles of the diffused chemicals at different locations on the robot body is studied. The results of this work provide crucial information required to determine the number, size, and location of the required micro-valves.