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Related Experiment Video

Updated: May 7, 2026

Light-driven Molecular Motors on Surfaces for Single Molecular Imaging

Light-driven Molecular Motors on Surfaces for Single Molecular Imaging

Published on: March 13, 2019

Quantifying Photochemical Propulsion in Light-Powered Janus Micromotors.

Katherinne I Requejo^1,2,3, Cristhian Cañari-Chumpitaz^2,3,4, Vida Jamali^2,5

¹California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, California 94720, United States.

|May 5, 2026

Summary

This summary is machine-generated.

Light-activated Janus particles convert light into motion, offering insights into microscale engines. Researchers quantified propulsion dynamics and forces, establishing a framework for designing light-powered micromotors.

Keywords:

Janus micromotors active colloids force light-activated Janus particles optical tweezers self-propulsion

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Last Updated: May 7, 2026

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Published on: April 26, 2019

Area of Science:

Materials Science
Chemical Engineering
Nanotechnology

Background:

Active colloids convert light into motion, serving as models for nonequilibrium systems and microscale engines.
Understanding light-activated Janus particles is crucial for developing advanced micro-propulsion systems.

Purpose of the Study:

To quantify the propulsion dynamics and force generation of light-activated gold-titanium dioxide (Au-TiO2) Janus particles.
To investigate the influence of particle size, metal thickness, fuel concentration, and illumination wavelength on propulsion.
To establish a single-particle framework for quantifying active forces in photocatalytic Janus particles.

Main Methods:

Characterization of light-activated Au-TiO2 Janus particles and Au-PS@TiO2 analogues using varying parameters.
Measurement of propulsion velocities under different conditions.
Optical tweezers to measure transient propulsion forces on single particles.
Simulations to validate the role of transient forces in active motion.
Functionalization with DNA polymers to assess effects on directional motion.

Main Results:

Average velocities of 33.2 ± 2.99 μm s⁻¹, with instantaneous velocities up to ~100 μm s⁻¹.
Transient propulsion forces with a median of 4.5-6.2 pN, lasting 21-41 ms and reaching up to 20 pN.
Simulations confirmed the role of these forces in observed trajectories.
DNA functionalization enhanced directional motion by reducing rotational diffusion.

Conclusions:

Photochemical energy conversion at the Au-TiO2 interface governs particle propulsion.
A single-particle framework for quantifying active forces in photocatalytic Janus particles has been established.
Design principles for light-powered micromotors have been identified, paving the way for future applications.