Remote control of the air-water interface by means of a magnetic field

Scientists have developed a novel magnetic system for manipulating small volumes of fluids.

The Microfluidics Cluster of the University of the Basque Country (UPV/EHU) has developed an innovative system to remotely manipulate the air-water interface using an external magnetic field. The study is part of the European multidisciplinary project MAMI, in which groups and companies from six countries participate. The work is advertised on the cover of the prestigious academic journal ‘Langmuir’.

The study and development of hydrophobic surfaces are gaining great interest in fields such as the precise handling of small volumes of fluids. The activity of many scientists in this regard has been inspired by natural materials that repel water, such as lotus leaves.

The integration of magnetic properties in hydrophobic materials favors remote manipulation of the material while repelling water, providing new perspectives for possible applications. In this work carried out by a team that includes Udara Bimendra Gunatilake and Fernando Benito López, both from the UPV/EHU.

the Microfluidics Cluster of the UPV/EHU, “we have developed a novel system to be able to manipulate the air-water interface using an external magnetic field”, says Fernando Benito López, principal investigator of the Microfluidics Cluster of the UPV/EHU.

To do this, “we have generated a layer of hydrophobic magnetic nanoparticles capable of floating on the water-air interface and forming a stable water-solid-air interface. We have observed that this layer easily bends downwards when exposed to an external magnetic field. Thanks to this, the layer creates a structure reminiscent of a tornado, with an inverted conical shape which we have named ‘Magneto Twister’, explains Fernando Benito López. “This tornado-shaped structure behaves like a soft, elastic material that deforms or disappears with the applied magnetic field,” adds the UPV/EHU professor.

Image of the cover of the academic journal Langmuir, which refers to the research carried out by the team of Udara Bimendra Gunatilake and Fernando Benito López. (Image: Langmuir)

This is fundamental research with three major applications of this structure in real scenarios: “first of all, says Benito López, we have used the ‘Magneto Twister’ to manipulate drops of water in an aqueous medium without mixing them. We position the water droplets on top of the magnetic cone to move them in the aqueous medium and transport them to where we are interested. Once the water droplets are in the desired area, we could remove the magnetic field to carry out the reaction in a controlled part of that total volume of water.”

In addition, “the ‘twister’ was used to separate liquids within an open surface channel, which gives us the option of having independent reservoirs within a fluidic channel and of storing reagents that only mix when the external magnetic field is removed. for a chemical or biological reaction to take place”, explains Fernando Benito. “It would be something similar to a valve that opens and closes to control the movement of fluids in these channels and ducts in a controlled way on the microscale”, adds the UPV/EHU researcher.

Lastly, “the magnetic twister was used to collect and remove microplastics floating on the surface of the water, simply by moving the twister towards the microplastic to trap it,” says Benito López.

From the Microfluidics Cluster of the UPV/EHU they state that this work “opens new ways for the use of hydrophobic magnetic nanoparticles in applications assisted by the water-air interface”.

The study is titled “Magneto Twister: Magneto Deformation of the Water–Air Interface by a Superhydrophobic Magnetic Nanoparticle Layer.” And it has been published in the academic journal Langmuir. (Source: UPV/EHU)