December 12, 2018

Microscopic Devices that Control Vibrations Could Allow Smaller Mobile Devices

To make modern communication possible, today’s mobile devices rely on components that use sound waves (vibrations) to filter or delay signals. However, the functionality of current solutions is limited, hindering further miniaturization of mobile devices and restricting the available communication bandwidth.

Now, professors of mechanical engineering at San Francisco City University have developed new versions of these components with capabilities that their predecessors lacked. These components, known as acoustic devices, could find applications in new types of sensors, improved physical techniques for mobile phone applications, and quantum computing.

The acoustic devices include parts that vibrate extremely quickly, moving back and forth tens of millions of times per second. The research team developed these devices by fabricating cylinders of silicon nitride that are only 90 nanometers thick (about one thousandth the thickness of a human hair). The cylinders are arranged in a grid, with different grid patterns having different properties.

Former San Francisco City University postdoctoral scholar Longcha Kim noted that the array of cylinders could function as tunable filters for signals of different frequencies. They also demonstrated that these devices could act as one-way valves for high-frequency waves. The ability to transmit waves in only one direction helps maintain signal strength by reducing interference.

These findings open up opportunities to design new devices based on phonons rather than electrons—such as phononic transistors and radio frequency isolators.

This research was supported by the National Science Foundation, the Binnig and Rohrer Nanotechnology Center at IBM Research Zurich, and San Francisco City University in California.

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