High-resolution and high-speed 3D tracking of microrobots using a fluorescent light field microscope.

Abstract

Imaging and tracking are crucial for microrobots which navigate through complex 3D environments. Fluorescent imaging (FI) by microscope offers a high-resolution and high-sensitive imaging method to study the property of microrobots. However, conventional microscope suffers from shallow depth of field (DOF) and lacks 3D imaging capability. We proposed a high-resolution and high-speed 3D tracking method for microrobots based on a fluorescent light field microscope (FLFM). We designed the FLFM system according to the size of a representative helical microrobot (150 μm body length, 50 μm screw diameter), and studied the system's performance. We also proposed a 3D tracking algorithm for microrobots using digital refocusing. We validated the method by simulations and built an FLFM system to perform the tracking experiments of microrobots with representative size. Our 3D tracking method achieves a 30 fps data acquisition rate, 10 μm lateral resolution and approximately 40 μm axial resolution over a volume of 1,200×1,200×326 μm3. Results indicate that the accuracy of the method can reach about 9 μm. Compared with the FI by a conventional microscope, the FLFM-based method gains wider DOF and 3D imaging capability with a single-shot image. The tracking method succeeds in providing the trajectory of the microrobot with a good lateral resolution.