A Helical Microrobot with an Optimized Propeller-Shape for Propulsion in Viscoelastic Biological Media
Cyber Valley Research Group, Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
Micro, Nano, and Molecular Systems Group, Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany
Bionaut Labs Ltd., Los Angeles, CA 90034, USA
Author to whom correspondence should be addressed.
Robotics 2019, 8(4), 87; https://doi.org/10.3390/robotics8040087
Received: 5 September 2019 / Revised: 25 September 2019 / Accepted: 8 October 2019 / Published: 15 October 2019
(This article belongs to the Section Medical Robotics and Service Robotics)
One major challenge for microrobots is to penetrate and effectively move through viscoelastic biological tissues. Most existing microrobots can only propel in viscous liquids. Recent advances demonstrate that sub-micron robots can actively penetrate nanoporous biological tissue, such as the vitreous of the eye. However, it is still difficult to propel a micron-sized device through dense biological tissue. Here, we report that a special twisted helical shape together with a high aspect ratio in cross-section permit a microrobot with a diameter of hundreds-of-micrometers to move through mouse liver tissue. The helical microrobot is driven by a rotating magnetic field and localized by ultrasound imaging inside the tissue. The twisted ribbon is made of molybdenum and a sharp tip is chemically etched to generate a higher pressure at the edge of the propeller to break the biopolymeric network of the dense tissue.