THE MOST SENSITIVE NEMS

The yale researchers have demonstrated silicon based nano-cantilevers smaller than the wavelength of the light that operate on the photonic principleseliminating the need for the expensive laser setups and eleectronic transducers.

The work reported in an April 26 advance online publication of Nature Nanotechnology ushers in a new generation of tools for ultra-sensitive measurements at the atomic level.

In nanoelectromechanical systems(NEMS) the cantilevers are used as nano-scale diving boards for the molecules and these cantilevers bend and registers the change that can be measured and calibrated.This paper demonstrates how NEMS can be improved by using integrated photonics to sense the cantilever motion.

"The system we developed is the most sensitive available that works at room temperature. Previously this level of sensitivity could only be achieved at extreme low temperatures" said senior author Hong Tang assisant professor in the yale school of engineering and applied sciences.

Their system can detect as little deflection in the nano-cantilever sensors as 0.0001 Angstroms — one ten thousandth of the size of an atom.

The above picture shows the array of nano-cantilevers

and the light being collected at the photonic chip.

The light is made to pass through a nano-cantilever.The excited light photons tunnels through a nanometer gap and these photons are collected on a chip."Detecting the lightwave after this evanescent tunneling," says Tang, "gives the unprecedented sensitivity."

Construction of sensor multiplex:

A parallel array of 10 photonic cantilevers are inegrated o a single photonic wire.Each cantilever is of different length and registers its own tone.

"A multiplex format lets us make more complex measurements of patterns simultaneously — like a tune with chords instead of single notes," said postdoctoral fellow Mo Li, the lead author of the paper.

We don't need a laser to operate these devices.Very cheap LEDs will suffice.The LED light sources used by the laptop screen can be scaled in size and can be usd as the photonic chip.

This development reinforces the practicality of the new field of nanooptomechanics and points to a future of compact, robust and scalable systems with high sensitivity that will find a wide range of future applications — from chemical and biological sensing to optical signal processing.