Tuning a magnetic fluid with an electric field produces complex dissipative patterns that can be controlled
A suspension of nanoparticles of iron oxide is transformed into a model for the emergence of complex dissipative structures when exposed to an electric field.
Researchers from Aalto University have shown that a nanoparticle suspension can be used as a simple model to study the formation of patterns and structures in more complex non-equilibrium systems, such as living cells.
The new system will not only be useful for researching pattern processes, but also for a range of technological applications.
The mixture consists of an oily liquid containing iron oxide nanoparticles that are magnetized when exposed to a magnetic field.
Applying a voltage to this ferrofluid under the right conditions causes the nanoparticles to migrate, resulting in a concentration gradient in the mixture.
The ferrofluid must also contain docusate, a waxy chemical capable of transporting charge through the liquid.
The presence of docusate and a voltage across the ferrofluid resulted in a separation of electrical charges, with the iron oxide nanoparticles being negatively charged, according to the researchers.
Carlo Rigoni, a postdoc researcher at Aalto, says: “We did not expect that at all.”
“We are still confused as to why this is happening.”
We do not even know if the charges are split before the document is added or if it happens as soon as the voltage is turned on. “
The liquid is referred to as an electroferrofluid rather than a ferrofluid by the researchers to reflect its new sensitivity to electric fields.
The nanoparticles migrate as a result of the electrical reactivity, and the resulting differences in the nanoparticle concentration change the magnetic reactivity of the electroferrofluid.
As a result, application of a magnetic field across the electroferrofluid changes the distribution of the nanoparticles, with the exact pattern varying depending on the strength and orientation of the magnetic field.
In other words, the nanoparticle distribution is unstable and changes from one state to another when the external magnetic field changes slightly.
The combination of voltage and docusate made the liquid a non-equilibrium system that required a constant supply of energy to maintain its state – a dissipative system.
Electroferrofluids are of particular interest both scientifically and in terms of potential uses because of their unexpected dynamics.
“Since their discovery in the 1960s, ferrofluids have aroused the interest of scientists, engineers and artists.
We have now discovered a simple way to control their magnetic properties on the go by simply applying a small …
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