Optical chiral microrobot for out-of-plane rotation

Optical microrobots (OPTOBOTs) have garnered significant interest, particularly in the medical field, due to their potential for precise cell manipulation in various biological studies and microsurgical applications. Previously described OPTOBOTs demonstrate multiple degrees of freedom, yet improvements are needed, especially in achieving reliable out-of-plane rotation. Here, we propose an OPTOBOT design based on chirality that enables full-cycle out-of-plane rotations using optical tweezers. The OPTOBOT has an arrow-like structure with two handles aligned on the same axis, maintaining its horizontal orientation and facilitating controlled movement. Additionally, the OPTOBOT's tail is a chiral helix, which induces repetitive out-of-plane rotations around its longer axis when targeted by a laser beam that is due to broken axial parity. Finite element analysis is employed to design the OPTOBOT and assess its capacity to generate mono-directional high optical torque. Experimental results confirm various actuation modes, supporting future integration of OPTOBOTs in complex micromanipulation tasks.