A Centimeter-Scale Inspection Robot for Locomotion in Viscous Fluids

Nature has inspired many designs for micro-robot locomotion, particularly helical propulsion inspired by Escherichia coli and spermatozoa, which has found widespread applications in medical micro-robots for generating thrust at low Reynolds numbers. However, the design and fabrication of small robots for inspection tasks, especially in industrial settings filled with highly viscous liquids, remain challenging. In this paper, we propose a robot capable of locomotion in constrained environments filled with high-viscosity fluids. The robot is propelled by two helical propellers, enabling it to move effectively at low Reynolds numbers. The optimal parameters for the helical propellers are analyzed using Resistive Force Theory (RFT), and structures are designed and experimentally validated accordingly. Finite element analysis is employed to determine the suitable body for the robot. The robot prototype is fabricated using 3D printing. Finally, locomotion experiment was conducted to validate the feasibility of the robot moving in viscous liquid.