Illustration of ultrasensitive optical interrogation of the motions of atomically thin drumhead nanoelectromechanical resonators (made of atomic layers of MoS2 semiconductor crystals). Source: Case Western Reserve University
A research team from Case Western Reserve University developed “drumheads” that are atomically thin and can receive and transmit signals across a radio frequency range that humans are unable to hear. The drumhead is tens of trillions times smaller in volume and 100,000 times thinner than a human eardrum.
This new drumhead is a big development for the next generation of ultralow-power communications and sensory devices. It allows for these new devices to have greater detection and tuning ranges. The main problem facing developers attempting to create mini, ultralow-power communications have been the measurements, limits and scaling for all transducers.
"Sensing and communication are key to a connected world," said Philip Feng, an associate professor of electrical engineering and computer science and corresponding author on a paper about the work published March 30 in the journal Science Advances. "In recent decades, we have been connected with highly miniaturized devices and systems, and we have been pursuing ever-shrinking sizes for those devices."
"In the end, we need transducers that can handle signals without losing or compromising information at both the 'signal ceiling' (the highest level of an undistorted signal) and the 'noise floor' (the lowest detectable level)," Feng said.
The team was not focusing on a specific device that is on the market, but, rather, the development was focused on measurements, limits and scaling, which are important for transducers.
The next level transducers may take up to ten more years to be completely finished. But the new drumheads have already proved to be able to operate at the smallest scale so far developed.
This work has shown the highest reported dynamic range for vibrating transducers of the type. Until now, this has only been successfully operated with larger transductors at much lower frequencies.
"What we've done here is to show that some ultimately miniaturized, atomically thin electromechanical drumhead resonators can offer remarkably broad dynamic range, up to ~110dB, at radio frequencies (RF) up to over 120MHz," Feng said. "These dynamic ranges at RF are comparable to the broad dynamic range of human hearing capability in the audio bands."
The new drumheads are made out of atomic layers of semiconductor crystals with a 1-micron diameter. To assemble the drumheads, the individual atomic layers from a bulk semiconductor are exfoliated with nanofabrication and micromanipulation techniques. These techniques suspend the atomic layers over micro-cavities that are defined by a silicon wafer. This makes the electrical contacts with the device.
The atomically thin RF resonators are currently being tested at the Case Western Reserve. So far, they are showing frequency “tenability.”
The drumheads only require picoWatt (pW, 10^-12 Watt) up to nanoWatt (nW, 10^-9 Watt) level of RF power in order to sustain high-frequency oscillations.
"Not only having surprisingly large dynamic range with such tiny volume and mass, they are also energy-efficient and very 'quiet' devices," Feng said, "We 'listen' to them very carefully and 'talk' to them very gently."
The paper on this research was published in the journal Science Advances.
