Making Water Droplets Dance
July 23, 2013

Ferrofluid Experiment Evolves New Patterns

[ Watch the Video: Magnetic Droplets on a Superhydrophobic Surface ]

Enid Burns for - Your Universe Online

Scientists are experimenting with non-dissapative droplet patterns to study reversible switching between static and dynamic self-assembly. Researchers from Aalto University and Paris Tech studied water droplets containing nanoparticles on a strong water repellent surface to observe the self-assembly process.

A video demonstrating the mesmerizing phenomena was posted on redOrbit. The patterns formed by the Ferrofluid droplets was described as looking like the drops are dancing, and captivating to watch.

The droplets were placed on water repellent surfaces that made them align in various static and dynamic structure patterns using periodically oscillating magnetic fields. Researchers created this situation of reversible switching between static and dynamic self-assembly for the first time.

"We are conducting this line of research because it opens up a way to create new responsive and intelligent systems and materials," said Dr. Robin Ras of Aalto University in Finland, in a statement about the research.

Researchers believe the process is interesting to both scientists and industry, for the possibilities that self-assembly, in which multiple components form organized structures or patterns without external direction, presents for development of new components.

"The structure formation can either be static, driven by energy minimization, or dynamic, driven by continuous energy feed. Over the years we have managed to create functional materials based on static self-assembled hierarchies. This model system paves the way towards even more versatile dynamic materials, wherein the structures are formed by feeding energy," said Academy Professor Olli Ikkala, in a statement about the research.

The new model system opens up new areas for researchers to study. The demonstration of the static droplet patterns "can transform reversibly into dynamic ones when energy is fed to the system via an oscillating magnetic field," the research brief explained. "The transition was observed to be complex and the most complicated patterns emerged when the energy feed was just enough to enter the dynamic self-assembly regime."

The work is part of the doctoral thesis of Jaakko Timonen at the Aalto University Department of Applied Physics, and was just completed. The research is multidisciplinary, combining proficiency in magnetic nanoparticle synthesis, superhydrophobic surfaces, and deep understanding of self-assemblies.

The findings of the research were published in Science.

Self-assembly is described as "a process in which interacting bodies are autonomously driven into ordered structures."

"Static structures such as crystals often form though simple energy minimization, whereas dynamic ones require continuous energy input to grow and sustain. Dynamic systems are ubiquitous in nature and biology but have proven challenging to understand and engineer."

If the systems are able to be better understood, the self-assembly process can be applied to production of new components and materials that can form and heel themselves. More research is required to determine applications where the self-assembling droplets can be put to use in a commercial format. Dynamic self-assembly has been suggested as a route to adaptive systems, according to the researchers. The dynamic self-assembly shows advances over static self-assembly.