Numerical design of magnetic-field-gradient-guided branch targeting of Au/Ni–SiO2 Janus microrobots in a bifurcating microchannel
- 1School of Electronic and Information Engineering, University of Science and Technology Liaoning Anshan 114051 China
Abstract
The controllable branch guidance of magnetic Janus microrobots in bifurcating microchannels is governed by the coupled effects of background advection, magnetophoretic migration and particle structure. Here, a three-dimensional numerical framework was developed to investigate the magnetically controlled transport of Au/Ni–SiO2 Janus microrobots in an idealised low-Reynolds-number bifurcating microchannel. An equivalent three-axis Helmholtz–Maxwell coil model was used to reconstruct an oblique magnetic-field gradient directed towards the target branch, and the resulting electromagnetic field was coupled with particle tracking. Over 0.5–7.0 T m−1, the reconstructed gradients closely reproduced the prescribed values, whilst the magnetic flux density remained above the adopted near-saturation criterion for Ni. For the baseline microrobot with a 120 nm Ni layer, the target-branch transport efficiency increased from 42.67% at 1.5 T m−1 to 100% at 7.0 T m−1. Increasing the inlet velocity from 0.25 to 1.50 mm s−1 shifted the guidance response towards higher gradients, reflecting stronger competition between axial advection and lateral magnetophoretic migration. Increasing the Ni-layer thickness from 150 to 390 nm raised the magnetic Ni volume fraction from 8.45% to 20.74% and reduced the minimum tested gradient for complete target-branch transport from 5.5 to 2.5 T m−1, a reduction of approximately 54.5%. Mechanistic analysis showed that the increase in magnetic moment substantially exceeded the increase in hydrodynamic resistance, and the transport data for different Ni-layer thicknesses were largely represented by a common response using a dimensionless magnetic-guidance parameter. These results provide a quantitative basis for co-optimising microrobot magnetic structure, background flow and external magnetic actuation.
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BibTeX
@article{yang2026numerical,
title = {{Numerical design of magnetic-field-gradient-guided branch targeting of Au/Ni–SiO2 Janus microrobots in a bifurcating microchannel}},
author = {Junbo Yang and Meijuan Li and Yonghui Yang and Xue-Bo Chen},
journal = {RSC advances},
year = {2026},
month = oct,
doi = {10.1039/d6ra08407a},
url = {https://europepmc.org/article/PMC/PMC13659811},
note = {CC BY},
}
RIS
TY - JOUR
TI - Numerical design of magnetic-field-gradient-guided branch targeting of Au/Ni–SiO2 Janus microrobots in a bifurcating microchannel
AU - Junbo Yang
AU - Meijuan Li
AU - Yonghui Yang
AU - Xue-Bo Chen
PY - 2026
DA - 2026/10/13
JO - RSC advances
DO - 10.1039/d6ra08407a
UR - https://europepmc.org/article/PMC/PMC13659811
AB - The controllable branch guidance of magnetic Janus microrobots in bifurcating microchannels is governed by the coupled effects of background advection, magnetophoretic migration and particle structure. Here, a three-dimensional numerical framework was developed to investigate the magnetically controlled transport of Au/Ni–SiO2 Janus microrobots in an idealised low-Reynolds-number bifurcating microchannel. An equivalent three-axis Helmholtz–Maxwell coil model was used to reconstruct an oblique magnetic-field gradient directed towards the target branch, and the resulting electromagnetic field was coupled with particle tracking. Over 0.5–7.0 T m−1, the reconstructed gradients closely reproduced the prescribed values, whilst the magnetic flux density remained above the adopted near-saturation criterion for Ni. For the baseline microrobot with a 120 nm Ni layer, the target-branch transport efficiency increased from 42.67% at 1.5 T m−1 to 100% at 7.0 T m−1. Increasing the inlet velocity from 0.25 to 1.50 mm s−1 shifted the guidance response towards higher gradients, reflecting stronger competition between axial advection and lateral magnetophoretic migration. Increasing the Ni-layer thickness from 150 to 390 nm raised the magnetic Ni volume fraction from 8.45% to 20.74% and reduced the minimum tested gradient for complete target-branch transport from 5.5 to 2.5 T m−1, a reduction of approximately 54.5%. Mechanistic analysis showed that the increase in magnetic moment substantially exceeded the increase in hydrodynamic resistance, and the transport data for different Ni-layer thicknesses were largely represented by a common response using a dimensionless magnetic-guidance parameter. These results provide a quantitative basis for co-optimising microrobot magnetic structure, background flow and external magnetic actuation.
SN - 2046-2069
ER -