Performance Estimation and Ex Vivo Validation of Untethered Magnetic Robots in Soft Tissue

Area of Science:

• Biomedical Engineering
• Robotics
• Soft Matter Physics

Background:

• Untethered magnetic robots (UMRs) require synchronized rotation for navigation in soft tissues.
• The step-out frequency limits propulsion efficiency and control stability.
• Brain tissue's viscoelastic properties pose challenges for UMR control.

Purpose of the Study:

• To develop an empirical model for predicting the step-out frequency of UMRs in ex vivo brain tissue.
• To establish a relationship between robot geometry, tissue viscoelasticity, and magnetic synchronization limits.
• To support the clinical translation of magnetic microrobots for brain interventions.

Main Methods:

• Utilized Buckingham Pi dimensional analysis to derive dimensionless groups.
• Developed an empirical model based on robot geometry and tissue viscoelasticity.
• Experimentally validated the model using spiral-type UMRs in gelatin phantoms.

Main Results:

• Step-out frequency decreases exponentially with increasing tissue stiffness.
• Observed frequencies ranging from ~30 Hz (400 Pa) to <1 Hz (1600 Pa).
• The model allows rapid estimation of UMR performance limits.

Conclusions:

• The developed model accurately predicts UMR step-out frequency in brain-like viscoelastic media.
• This framework facilitates efficient design and parameter optimization for UMRs.
• Enables better evaluation of magnetic microrobot capabilities for neurosurgery.