Fig 1. Soft robotic sperm switches between planar to helical flagellar propulsion under the influence of controlled magnetic fields.

(a) Scanning electron microscopy images of the robotic sperm indicate similar morphology to that of biological sperm cells. The robotic sperm consists of a magnetic head and a flexible flagellum, and is fabricated using polystyrene. Magnetic particles are impeded into the head to provide magnetization (M). (b) Planar flagellar propulsion is achieved by applying in-plane uniform field (B) along direction of motion with a sinusoidally varying orthogonal component. (c) Wobbling of the head of the robotic sperm is achieved by applying out-of-plane field.