Scientists make nanofibers using fridge magnet and ferrofluid

[ella_maru]

Researches from the University of Georgia, Princeton University and Oxford University report a new method for nanofiber production using a permanent magnet and ferrofluid – magnetospinning. Results of this research are published in Advanced Materials journal - http://onlinelibrary.wiley.com/doi/10.1002/adma.201500374/abstract

 

A ferrofluid is a colloidal dispersion of stabilized magnetic nanoparticles that responds to an external magnetic field: above a critical value for a uniform field the surface of the ferrofluid deforms and a liquid spike is formed on the surface. In addition, as a magnet approaches an interface, the field is nonuniform, the interface always deforms, so the spike moves towards the magnet and forms a liquid bridge. This instability was explored in this work in a new method for drawing polymeric nano and microfibers in which the magnetic force generated by a permanent magnet is used to draw fibers with controlled diameters in the 0.05–5 µm range. As the magnet approaches the ferrofluid the magnetic force attracts the droplet towards the magnet and a liquid bridge between the magnet and the needle is formed. The magnet moves away and draws the polymer fiber while the solvent evaporates. The resulting nanofibers are spooled on a reel that is attached to the opposite side of the stage.

 

 

 

The new method provides excellent control over the fiber diameter and is compatible with a range of polymeric materials and polymer composite materials including biopolymers. This research showcases new technique and demonstrates its advantages to the scientific community. For example, polymers with low dielectric constant cannot be electrospun without adding high dielectric constant ingredients but can be easily magnetospun, for example Teflon© fluoropolymer fibers that are ideal for the design of superhydrophobic materials. Owing to its simplicity and low costs, magnetospinning set-up could be installed in any non-specialized labs for broader uses of magnetospun nanofibers in different methods and technologies. Electrospinning is the most popular method to produce nanofibers in labs now. The total cost of a laboratory electrospinning system is above ~$10K. In contrast, it is possible to build a magnetospinning set-up, such as we utilize, by just using a $30 rotating motor and a $5 permanent magnet. No special equipment is needed for magnetospinning.

Researches showed that the productivity and scalability in magnetospinning is comparable with electrospinning methods and demonstrated universality of the new method by fabricating several examples of different polymeric fibers, including Teflon© fibers, fibers with aligned carbon nanotubes, silver nanowires, and porous fibers – all obtained with the same experimental set-up

 

[Phi for All]

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Moderator Note

Moved from Theoretical Physics to Science News.

[Enthalpy]

Interesting news, ella_maru, thanks! And by the way, welcome here!

 

I have an impression that spinning could be much faster if the magnet didn't rotate as a part of the coil. Would it be possible to separate both functions, with an immobile magnet and a spindle downstream? This may also permit many fibres simultaneously.

 

I wouldn't concentrate on Ptfe, just as a feeling. The magnetic particles may degrade its hydrophobic properties. Anyway, a new process opens new uses, while it's difficult to outperform existing processes in existing uses. Could the fibres catch from the blood or from a chemical unwanted substances where a tiny magnet has been attached by a selective protein? Done with a big magnet presently. Or store data in 3D?

 

Very nice: if it could make a solar sail lighter than the present films. 7.5µm polymer is still heavy, but a conductive mesh or felt would reflect light even if very hollow, provided the holes are <0.5 wavelength. Few additional graphite fibres per metre would give the strength.

 

Could the embedded magnetic particles that, in a fine mesh or felt, reside very near to the outside medium, make some difficult chemical separations through the strong magnetic field gradient? As a model, porous high-temp superconductors separate nitrogen and paramagnetic oxygen.

[ella_maru]

Thanks! I am the first author on this article

 

It is very good idea to separate these 2 processes and that is how I started working on magnetospinning just trying to make fiber with a magnet. This way however I could only make one fiber and then I needed to collect it somehow and that us why i tried rotating the magnet. I am still thinking on how I can separate these 2 processes and if I come up with something it will be one more article You may come up with idea first and write an article

 

 

 

Interesting news, ella_maru, thanks! And by the way, welcome here!

 

I have an impression that spinning could be much faster if the magnet didn't rotate as a part of the coil. Would it be possible to separate both functions, with an immobile magnet and a spindle downstream? This may also permit many fibres simultaneously.

 

I wouldn't concentrate on Ptfe, just as a feeling. The magnetic particles may degrade its hydrophobic properties. Anyway, a new process opens new uses, while it's difficult to outperform existing processes in existing uses. Could the fibres catch from the blood or from a chemical unwanted substances where a tiny magnet has been attached by a selective protein? Done with a big magnet presently. Or store data in 3D?

 

Very nice: if it could make a solar sail lighter than the present films. 7.5µm polymer is still heavy, but a conductive mesh or felt would reflect light even if very hollow, provided the holes are <0.5 wavelength. Few additional graphite fibres per metre would give the strength.

 

Could the embedded magnetic particles that, in a fine mesh or felt, reside very near to the outside medium, make some difficult chemical separations through the strong magnetic field gradient? As a model, porous high-temp superconductors separate nitrogen and paramagnetic oxygen.

[Enthalpy]

Good job! There must be plenty of funny things to do with the tiny fibres.

 

Maybe you could make metallic nanofibres, because some permanent magnet materials (Sm-magnets, maybe AlNiCo but they demagnetize) can be used at a temperature where a few metals have already molten. Zinc is a little bit too hot, but a zinc eutectic - and of course things like In, Sn and Pb alloys and the like.

 

I don't need to tell that nano Zn oxidizes in air.

 

When I have time I'll make a sketch about the magnets. And, no, I won't publish it in a review, because I don't even receive any review - I'm an armchair inventor.

 

But first, did you check whether you actually need the magnet, once the process has started? Since you get the same fibre diameter near and far of the magnet, I vaguely intuite that the nano ferromagnets in the fibre do it alone.

[Enthalpy]

Here are three setups that produce a permanent induction along the fibre.

 

 

The electromagnet is more flexible but needs the usual 800A*t for each T*mm, so reducing the gap is important.

Edited May 17, 2015 by Enthalpy