Technical Review: One-step microfluidic synthesis of Janus particles with controllable magnetic nanoparticle proportion and their magnetoresponsive motion
- perryt6
- Sep 12
- 3 min read
Authors: Wenze Wu, Zheng Tang, Jiankai Xu, Likai Hou
Affiliation: College of Metrology Measurement and Instrument, China Jiliang University, Hangzhou, China
Background Introduction
This research falls within the interdisciplinary field of microfluidics and materials science, specifically focusing on the synthesis and characterization of magnetic Janus particles. Janus particles are anisotropic particles with distinct bi-compartmental structures exhibiting different physical, chemical, or optical properties in each hemisphere. The field has gained significant attention due to applications in biomedicine, micro-nano mechanics, and environmental protection. Magnetic Janus particles represent a particularly valuable subset due to their controllability in fluid media through external magnetic fields, making them highly suitable for drug delivery, micromotors, and material synthesis applications. However, traditional synthesis methods such as flame synthesis and phase separation suffer from limited morphological control and complex preparation processes. Microfluidic approaches offer a compelling alternative, with superior monodispersity and controllable morphology.
Materials and Methodology
The researchers highlighted a novel microfluidic device featuring an innovative theta-shaped glass capillary structure. This was used to combine two oil phases as part of an oil-in-water (O-W) emulsion, and it permitted fine volume ratio tuning for the resulting Janus droplets. The two oil phases both consisted of ETPTA and UV initiator, with one of them additionally suspending Fe₃O₄ nanoparticles in this solution. Meanwhile, the aqueous phase contained 5 wt% polyvinyl alcohol as a surfactant. The O-W emulsion was carried out by controlled mixing in the previously mentiond microfluidic device, followed by UV curing to solidify the Janus droplets and characterization such as size analysis, magnetoresponsive characterization, and functional analysis.
Results
Synthesis Optimization
Synthesis optimization revealed that Janus particles with different magnetic nanoparticle proportions (QO1:QO2 ratios from 1:1 to 1:4) maintained stable bi-compartmental structures. The average particle diameter after UV curing was 135 µm, with droplet diameter linearly decreasing from 165 µm to 112 µm as water phase flow rate increased from 3 to 11 mL/h. Remarkably, the particles demonstrated exceptional monodispersity with a coefficient of variation less than 2%, indicating highly uniform size distribution.
Magnetoresponsive Characterization
Magnetoresponsive characterization demonstrated significant correlation between Fe₃O₄ content and movement velocity under magnetic fields. Particles with 1:1 magnetic ratio completed 2800 µm movement in 8.55 seconds, while 1:4 ratio particles required 29.73 seconds. Under rotating magnetic fields, particles exhibited excellent angular tracking with velocities ranging from 0.65 to 7.85 rad/s, completing full rotations within 0.8 seconds. This anisotropic behavior results from magnetic torque acting selectively on the magnetic domain while leaving the non-magnetic domain unaffected.
Functional Analysis
Functional applications successfully demonstrated droplet manipulation capabilities through L-ascorbic acid redox reactions. The magnetic Janus particles could precisely control DSSH droplet movement along predetermined trajectories, enabling sequential reactions with five different L-ascorbic acid samples. The particles exhibited remarkable loading performance, capable of transporting droplets up to 400 times their own volume, with distinct color gradients indicating successful stepwise reactions.
Conclusion
Wu and colleagues demonstrated promising results with their novel microfluidic device. It permitted unprecedented control over magnetic nanoparticle distribution while maintaining exceptional particle uniformity. This permitted superb controllability of droplets for directed transport, with potential applications in targeted drug delivery, smart catalysis, and micro-nano robotics.
This paper utilized the PreciGenome iFlow Controller for droplet generation. Fine flow rate control with steady pressure delivery are both essential for monodisperse droplets and tuning their morphology.
For further details, check out the link to the article here:
Comments