Polarity-resolved imaging reveals active transport in catalytic Janus nanomotors
15 affiliations
- 1School of Chemical and Biomolecular Engineering
- 2Georgia Institute of Technology
- 3Howard Hughes Medical Institute
- 4University of California, Berkeley
- 5Department of Chemistry
- 6Molecular Foundry
- 7Lawrence Berkeley National Laboratory
- 8Bar-Ilan University
- 9Department of Physics
- 10Jason Choy Laboratory of Single Molecule Biophysics
- 11Kavli Energy Nanoscience Institute
- 12Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory
- 13Department of Molecular and Cell Biology
- 14University of Chicago
- 15Pritzker School of Molecular Engineering
Abstract
Catalytic Janus motors that convert chemical energy into self-propulsion are promising platforms for targeted delivery, sensing, and environmental remediation. Miniaturizing these systems to the nanoscale is challenged by rotational diffusion (𝑫r ∝ 1/𝑹3) increasing faster than translational diffusion (𝑫t ∝ 1/𝑹), which destroys orientational memory. This raises the question of whether catalytic asymmetry can still bias the active displacement direction when orientational memory is short-lived. Answering it requires simultaneous knowledge of particle orientation and translational motion, yet current optical and ensemblebased methods cannot resolve catalytic cap orientation (particle polarity) of Janus nanomotors, leaving its relationship to propulsion direction experimentally inaccessible. Herein, we combine total internal reflection fluorescence (TIRF) microscopy to establish fuel-dependent activity under bulk conditions, with singleparticle visualization by liquid-phase transmission electron microscopy (LPTEM) to characterize active transport of platinum-polystyrene (Pt-PS) Janus nanomotors. TIRF measurements confirm fuel-dependent enhanced diffusion across a range of H2O2 concentrations (0 to 3 wt%). LPTEM analysis reveals superdiffusive transport (𝜶 =1.11) despite the heterogeneous interfacial energy landscape of the liquid-cell and identifies active intervals characterized by a Péclet number (𝑷𝒆) of ∼21. Frame-by-frame extraction of the platinum cap orientation during active displacements reveals a bias towards polystyrene-forward motion, consistent with self-phoretic mechanisms reported for Janus motors at the micron scale, while trajectory analysis yields an orientational persistence length of∼380 nm, corresponding to approximately three particle body lengths. These findings demonstrate that catalytic asymmetry continues to bias displacement direction even when thermal fluctuations limit orientational memory, providing a polarity-resolved mechanistic picture of Pt-PS propulsion at the 100 nm scale.
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BibTeX
@misc{panicker2026polarityresolved,
title = {{Polarity-resolved imaging reveals active transport in catalytic Janus nanomotors}},
author = {Isabel Panicker and Katherinne I. Requejo and Ricardo Ruiz and Assaf Ben-Moshe and Carlos Bustamante and A. Paul Alivisatos and Vida Jamali},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008309/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008309/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Polarity-resolved imaging reveals active transport in catalytic Janus nanomotors
AU - Isabel Panicker
AU - Katherinne I. Requejo
AU - Ricardo Ruiz
AU - Assaf Ben-Moshe
AU - Carlos Bustamante
AU - A. Paul Alivisatos
AU - Vida Jamali
PY - 2026
DA - 2026/09/04
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008309/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008309/v1
AB - Catalytic Janus motors that convert chemical energy into self-propulsion are promising platforms for targeted delivery, sensing, and environmental remediation. Miniaturizing these systems to the nanoscale is challenged by rotational diffusion (𝑫r ∝ 1/𝑹3) increasing faster than translational diffusion (𝑫t ∝ 1/𝑹), which destroys orientational memory. This raises the question of whether catalytic asymmetry can still bias the active displacement direction when orientational memory is short-lived. Answering it requires simultaneous knowledge of particle orientation and translational motion, yet current optical and ensemblebased methods cannot resolve catalytic cap orientation (particle polarity) of Janus nanomotors, leaving its relationship to propulsion direction experimentally inaccessible. Herein, we combine total internal reflection fluorescence (TIRF) microscopy to establish fuel-dependent activity under bulk conditions, with singleparticle visualization by liquid-phase transmission electron microscopy (LPTEM) to characterize active transport of platinum-polystyrene (Pt-PS) Janus nanomotors. TIRF measurements confirm fuel-dependent enhanced diffusion across a range of H2O2 concentrations (0 to 3 wt%). LPTEM analysis reveals superdiffusive transport (𝜶 =1.11) despite the heterogeneous interfacial energy landscape of the liquid-cell and identifies active intervals characterized by a Péclet number (𝑷𝒆) of ∼21. Frame-by-frame extraction of the platinum cap orientation during active displacements reveals a bias towards polystyrene-forward motion, consistent with self-phoretic mechanisms reported for Janus motors at the micron scale, while trajectory analysis yields an orientational persistence length of∼380 nm, corresponding to approximately three particle body lengths. These findings demonstrate that catalytic asymmetry continues to bias displacement direction even when thermal fluctuations limit orientational memory, providing a polarity-resolved mechanistic picture of Pt-PS propulsion at the 100 nm scale.
ER -