BRIAN BELL / SCIENCE PHOTO LIBRARY BRIAN BELL / SCIENCE PHOTO LIBRARY
Demonstration of ultrasonic levitation, showing polystyrene balls levitating above a loudspeaker. The balls can be put back in position after being removed by the forceps at left. Ultrasonic levitation is being developed to help grow tissue cultures and for other biomedical applications. The system comprises a loudspeaker (bottom) that emits high-frequency ultrasound, and a reflector (centre). By precisely controlling the sound a stable standing wave (seen on oscilloscope display in background) can be formed in the cavity. This wave has fixed regions of low and high pressure, and in specific regions the force of the wave balances gravity, holding the balls aloft. This system is being designed for culturing human cells and tissues, such as cartilage, which can be grown surrounded by culture medium. The shape of the growing tissue can be precisely controlled by varying the sound. This helps to grow implants and grafts tailored exactly for their intended location. Filmed at the University of Southampton, UK, in 2016.
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