Wall of sound

(Nanowerk News) Scientists have been using sound to levitate small objects for 30 years, but researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have improved upon this container-free approach. They have found a way to enable experiments that use less material, decreasing costs and opening the door to new research.
The researchers’ work began two years ago and was funded by Argonne’s Laboratory Directed Research and Development (LDRD) Program.
Through their work, they’ve been able to manipulate smaller samples than ever before — and to levitate more than one at a time, allowing researchers to rapidly screen a variety of droplets at once.
intense sound forces to levitate or hold samples in 'container-free' experiments
Argonne physicist Anthony DiChiara and his team are using Laboratory Directed Research and Development (LDRD) funds to use very intense sound forces to levitate or hold samples in “container-free” experiments. (Image: Argonne National Laboratory)
“We are using very intense sound forces to levitate or hold these samples so that there is nothing solid that needs to come into contact with them,” said assistant physicist Anthony DiChiara. “The idea is not new, but because of recent developments, this technology today is much more feasible.”
"My hope is that the instrumentation we’ve developed will have an impact on a broad range of fields because the idea of efficiently initiating and watching a reaction happen can have a profound impact on so much of the technology that shapes our lives,” he said. “Whether it’s knowing how to make better conductive polymers for printing a novel circuit or making better cheaper medicines, it all boils down to finding ways to better understand how and why materials form from their initial components.”
Supratik Guha, Argonne’s Senior Science Advisor, director of its Nanoscience & Technology division and Center for Nanoscale Materials, a DOE Office of Science User Facility, said the funding bolsters new and innovative research that can lead to critical breakthroughs that win the attention — and potential financial support — from the Department of Energy itself.
“LDRD funding is one way that national labs can explore new areas that might steer their future research directions,” he said.
Vivian Sullivan, LDRD program manager at Argonne, said the funding is critical in helping to foster creativity and out-of-the-box thinking among scientists and researchers.
“The container-free experiment is particularly fascinating,” she said. “Using sound instead of a physical container could potentially let all sorts of things become possible that weren’t before.”
Previously, scientists were able to levitate samples that were a few millimeters wide. Argonne scientists seek to manipulate far smaller samples, those that are just a couple hundred microns in diameter. The goal is to minimize the amount of sample required for a complete experiment.
Argonne researchers are also able to use sound to move the material up and down, allowing them to hold several droplets at once. The benefit of this is that multiple samples can be loaded into the trap at any given time — and screening can be automated.
DiChiara said the technology can be used in the area of material synthesis in which scientists create new materials in a laboratory setting and use X-ray characterization methods to watch the synthesis happen. Such a technique may be used to optimize research involving nanoparticles, polymers and pharmaceuticals by reducing the amounts of materials used while a particular reaction is being optimized.
In addition to driving down the cost by using less material, a container-free environment can help eliminate changes that might occur when a sample comes into contact with a surface. This is particularly important when extremely small amounts of material are used since the geometry leads to a higher portion of material in contact with the walls of a vessel.
“Contact between the sample and the container wall can change the energetics of the reaction in a way that changes the outcome,” DiChiara said. “The chemistry occurring at the interface of the vessel may not be the same as that occurring elsewhere and it may complicate or change the outcome of an experiment. Removing the container offers a potentially cleaner environment to watch how a reaction proceeds.”
Source: Argonne National Laboratory
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