Performance Estimation and Ex Vivo Validation of Untethered Magnetic Robots in Soft Tissue
11 affiliations
- 1RAM—Robotics and Mechatronics University of Twente Enschede The Netherlands
- 2Radboud University Medical Center Nijmegen The Netherlands
- 3Technical Medical Centre University of Twente Enschede The Netherlands
- 4Mesoscale Chemical Systems, MESA+ Institute University of Twente Enschede The Netherlands
- 5Department of Physics German University in Cairo New Cairo Egypt
- 6Department of Dentistry‐Regenerative Biomaterials Radboud University Medical Center Nijmegen The Netherlands
- 7LipoCoat B.V. Enschede The Netherlands
- 8Department of Molecules and Materials, Biointerface Chemistry Lab University of Twente Enschede The Netherlands
- 9Triticum Medical Ramat HaSharon Israel
- 10The Hebrew University of Jerusalem Rehovot Israel
- 11Department of Surgery, Division of Vascular and Transplant Surgery Radboud University Medical Center Nijmegen Nijmegen The Netherlands
Abstract
The navigation and control of untethered magnetic robots (UMRs) within soft brain tissue critically depend on their ability to maintain synchronized rotation under applied rotational magnetic fields. The fundamental upper limit of this magnetic synchronization, known as the step‐out frequency, directly affects propulsion efficiency and control stability. This study presents an empirical model for predicting the step‐out frequency of UMRs operating in ex vivo brain tissue with viscoelastic properties representative of the in vivo environment. Using Buckingham Pi dimensional analysis, we derive a compact set of dimensionless groups that capture the effects of robot geometry and tissue viscoelasticity, with magnetic torque used as the scaling basis. Experimental validation with spiral‐type UMRs in gelatin‐based phantoms shows that the step‐out frequency decreases exponentially, from approximately 30 Hz in low‐stiffness media (complex shear modulus ∼400 Pa) to below 1 Hz in high‐stiffness media (complex shear modulus ∼1600 Pa). The found relationship allows for rapid estimation of robot performance limits using a single calibration point, enabling efficient evaluation of robot design and actuation parameters. The resulting framework supports the clinical translation of magnetic microrobots for precise therapeutic and surgical interventions in brain tissue.
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BibTeX
@article{ligtenberg2026performance,
title = {{Performance Estimation and Ex Vivo Validation of Untethered Magnetic Robots in Soft Tissue}},
author = {Leendert‐Jan W. Ligtenberg and Thijs J. van der Burg and Stijn Y. Kolkman and Santiago Saavedra Castano and David Fernandez Rivas and Anke Klingner and Roger M. L. M. Lomme and Lucas S. Joziasse and Dorothee Wasserberg and H. Remco Liefers and Doron Ben Ami and Udi Sadeh and Oded Shoseyov and Giulio Dagnino and Pascal Jonkheijm and Jurgen J. Fütterer and Stefano Stramigioli and J. Frank W. Nijsen and Michiel C. Warlé and Islam S. M. Khalil},
journal = {Advanced Science},
year = {2026},
month = aug,
doi = {10.1002/advs.77011},
url = {https://doi.org/10.1002/advs.77011},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Performance Estimation and Ex Vivo Validation of Untethered Magnetic Robots in Soft Tissue
AU - Leendert‐Jan W. Ligtenberg
AU - Thijs J. van der Burg
AU - Stijn Y. Kolkman
AU - Santiago Saavedra Castano
AU - David Fernandez Rivas
AU - Anke Klingner
AU - Roger M. L. M. Lomme
AU - Lucas S. Joziasse
AU - Dorothee Wasserberg
AU - H. Remco Liefers
AU - Doron Ben Ami
AU - Udi Sadeh
AU - Oded Shoseyov
AU - Giulio Dagnino
AU - Pascal Jonkheijm
AU - Jurgen J. Fütterer
AU - Stefano Stramigioli
AU - J. Frank W. Nijsen
AU - Michiel C. Warlé
AU - Islam S. M. Khalil
PY - 2026
DA - 2026/08/14
JO - Advanced Science
DO - 10.1002/advs.77011
UR - https://doi.org/10.1002/advs.77011
AB - The navigation and control of untethered magnetic robots (UMRs) within soft brain tissue critically depend on their ability to maintain synchronized rotation under applied rotational magnetic fields. The fundamental upper limit of this magnetic synchronization, known as the step‐out frequency, directly affects propulsion efficiency and control stability. This study presents an empirical model for predicting the step‐out frequency of UMRs operating in ex vivo brain tissue with viscoelastic properties representative of the in vivo environment. Using Buckingham Pi dimensional analysis, we derive a compact set of dimensionless groups that capture the effects of robot geometry and tissue viscoelasticity, with magnetic torque used as the scaling basis. Experimental validation with spiral‐type UMRs in gelatin‐based phantoms shows that the step‐out frequency decreases exponentially, from approximately 30 Hz in low‐stiffness media (complex shear modulus ∼400 Pa) to below 1 Hz in high‐stiffness media (complex shear modulus ∼1600 Pa). The found relationship allows for rapid estimation of robot performance limits using a single calibration point, enabling efficient evaluation of robot design and actuation parameters. The resulting framework supports the clinical translation of magnetic microrobots for precise therapeutic and surgical interventions in brain tissue.
SN - 2198-3844
ER -