Design of Magnetic Tumbling Microrobots for Complex Environments and Biomedical Applications

Chenghao Bi, Purdue University

Abstract

The mobility and biomedical applications of a microscale magnetic tumbling (µTUM) robot capable of traversing complex terrains in dry and wet environments is explored. Roughly 800 x 400 x 100 µm in size, the robot is fabricated using standard photolithography techniques and consists of a rectangular polymeric body with embedded NdFeB particles. Static force analysis and dynamic modeling of its motion characteristics are performed with experimental verification. Techniques for simulating the intermittent, non-contact behavior of tumbling locomotion are used to find an optimized design for the microrobot, reducing time and resources spent on physical fabrication. When subject to a magnetic field as low as 3 mT, the microrobot is able to translate at speeds of over 30 body lengths/s (24 mm/s) in dry conditions and up to 8 body lengths/s (6.8 mm/s) in wet conditions. It can climb inclined planes up to 60◦ in wet conditions and up to 45◦ in dry conditions. Maximum open loop straightline trajectory errors of less than 4% and 2% of the traversal distance in the vertical and horizontal directions, respectively, were also observed. Full two-dimensional directional control of the microrobot was shown through the traversal of a P-shaped trajectory. The microrobot's real-time position can be accurately tracked through visual occlusions using ultrasound imaging. When applied as a coating, a fluorescein payload was found to diffuse over a two hour time period from the microrobot. Cytotoxicity tests also demonstrated that the microrobot's SU-8 body is biocompatible with murine fibroblasts. The microrobot's capabilities make it promising for targeted drug delivery and other in vivo biomedical applications.

Degree

M.Sc.

Advisors

Cappelleri, Purdue University.

Subject Area

Atmospheric sciences|Design|Electromagnetics|Immunology|Medical imaging|Oncology|Physics|Robotics|Therapy

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