Engineers have devised a system to gently manipulate biological nanoparticles a few nanometers in size using sound-induced electric fields.
Precisely controlling nanoparticles is a crucial capability for many emerging technologies. For example, the removal of exosomes and other tiny biological molecules from the blood could lead to new types of diagnostic tests for the early detection of tumors and neurodegenerative diseases. Placing engineered nanoparticles in a specific pattern before fixing them in place can help create new types of materials with highly tunable properties.
For more than a decade, Tony Jun Huang of Duke University in the United States has worked on the development of acoustic gripper systems that use sound waves to manipulate particles. However, it is difficult to push things with sound when they are smaller in size than some of the smaller viruses.
“Although we continue to use primarily sound, our acoustic-electronic nano-clamps use a very different mechanism than these previous technologies,” explains Joseph Rufo, from the aforementioned university and a member of the research team. “Now we not only use acoustic waves, but also electric fields with the properties of acoustic waves.”
Rather than using sound waves to directly move nanoparticles, the team, which also includes, among others, Peiran Zhang of Duke University, uses sound waves to create electric fields that provide the thrust. The new acoustic-electronic tweezers method works by placing a piezoelectric substrate (a thin material that creates electricity in response to mechanical stress) under a small, liquid-filled chamber. On the sides of the chamber are four transducers that send sound waves to the piezoelectric substrate.
These sound waves bounce off and interact with each other in such a way that they create a stable pattern. And since sound waves produce stresses in the piezoelectric substrate, they also generate electric fields. These couple with acoustic waves in a way that creates electric field patterns within the upper chamber.
This new biomedical device manipulates particles as small as a few nanometers through sound-induced electric fields. (Image: Peiran Zhang, Duke University)
“The vibrations of the sound waves also cause the electric field to dynamically alternate between positive and negative charges,” explains Zhang. “This alternating electric field polarizes the nanoparticles in the liquid, which helps to manipulate them.” (Source: NCYT from Amazings)