A Helical Microrobot with an Optimized Propeller-Shape for Propulsion in Viscoelastic Biological Media

Dandan Li,Tian Qiu,Moonkwang Jeong,Tingting Yu,Eran Oren

doi:10.3390/robotics8040087

Dandan Li, Tian Qiu + Show 3 more

Open Access

https://doi.org/10.3390/robotics8040087

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Abstract

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.

Highlights

Micro-/nano-robotics hold great potential in biomedical applications [1]
Leaving the linear viscoelastic (LVE) plateau at a strain of 20–100% suggests that irreversible deformation of the gel occurs, i.e., the gel network starts to break down
Helical structures are commonly used as propulsion units for micro-/nano-robotics

Summary

Introduction

Micro-/nano-robotics hold great potential in biomedical applications [1] They are minimally invasive, leaving minimal, or even no, surgical footprint. They can be wirelessly driven and controlled, which should enable a number of medical applications, including drug delivery, and in vivo sensing and stimulation, especially if they can be navigated into tissues. They may enable new surgical procedures that treat non-surgical diseases, such as infection or immune responses at the cellular level. The helical nanorobots have a diameter of ~500 nm, which is similar to the mesh size of the biopolymer network in the vitreous of the eye, they can propel

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