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34 || AWSAR Awarded Popular Science Stories - 2019
mechanical devices can be made to vibrate very much like loudspeakers using electrical signals. However, these devices vibrate at a much higher frequency, in the range of 100 mega Hertz (a unit of frequency) where FM radio channels work. The FM radio signals are audible through radio; however, the nanodevices require special techniques to detect their signals. The vibration frequency of the devices can be tuned by changing tension in the membrane, like tuning a guitar through tension in its string or tuning a musical drum. The mega Hertz frequency range gives these nanodevices an edge in terms of high sensitivity and precision. Since the devices are tiny, they are very sensitive to external stimuli and hence have great potential from being an ultra-sensitive sensor, such as a nano weighing machine for detecting the mass of a single protein molecule, to an excellent tool for studying complex quantum mechanics. In the quest to explore their
potential applications as an ultra-sensitive sensor and in quantum systems, we designed and performed experiments to study their extraordinary properties.
In our recent work, we
played nano drums. The
relevance of the work is
vast, and the history dates
back to the seventeenth
century. Christiaan Huygens’s
“Horologium Oscillatorium”
(1673) is considered as one
of the foundations of modern
mechanics. Huygens, the
inventor of pendulum clock,
described the synchronization
of pendulum clocks in his book. He observed that the pendulums in two of his clocks hung on the same wall used to get mysteriously synchronized over time, no matter how their
clocks began. The synchronization was the result of coupling between the pendula. The dynamics of the pendula were affected by each other’s motion through the exchange of energy between them. This coupling phenomenon is ubiquitous in nature, from synchronized flashing of fireflies, rhythmic beating of heart cells in biology to lasers and quantum computers in physics. The concept of coupling plays a crucial role in one of the most precise experimental setups on earth: Laser Interferometer Gravitational- Wave Observatory (LIGO), where the light is coupled to mechanics to detect gravitational waves. When a nano drum vibrates, multiple vibrational modes (equivalent to the notes in music) are generated and these modes have a corresponding frequency. The individual modes are analogous to a pendulum clock. Similar to the interaction between the coupled pendulum clocks hung on the wall, the modes
can also interact with each other through the tension in the drum membrane.
In a recently published research in Nano Letters in September 2019, we studied the coupling mechanism between the two vibrational modes of a nanoscale drum. For simplicity, we named the vibrational modes as mode 1 and mode 2. The mode interaction via tension in the drum membrane could be controlled electrically. In our experiment, we could precisely tune the coupling to enhance or reduce the energy exchange between the vibrational modes.
The coupling could be increased to such an extent that the energy between the two modes was exchanged more than 500 times back and forth before the information was lost to
Engineering is an ancient skill concerning design and structures, yet it is still evolving and constantly developing. Over the centuries, engineers have mastered the design and selection of materials to improve instruments. The devices that used to be of the size of a building are now available in pocket forms of mobiles and computers.