As the quest for the smallest material and basic components of matter accelerates, scientists around the world are currently faced with a more and more pressing issue – the lack of appropriate means of investigating single atoms and molecules. They require a tool that can detect even the smallest amounts of movement, as well as single electron spins, and creating such an instrument has proven to be a very difficult task over the years. But now, Yale researchers believe they may have developed such a method, which no longer relies on electric transducers and expensive laser setups in order to operate.

They have managed to get a proof-of-concept for silicon-based nano-cantilevers, which operate on the principles of photonics. Basically, this means that they are entirely controlled by light. The structures are smaller in size than the wavelength of visible light itself, the team has also announced, and this means that they could be operated as sensors in the next-generation of highly sensitive scanners, for a wide array of applications. The find was published yesterday, in the April 26th advance online publication of the scientific journal Nature Nanotechnology.

“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,” Yale School of Engineering and Applied Sciences Assistant Professor of Electrical and Mechanical Engineering Hong Tang, who is also the senior author of the new scientific paper, explained. He added that, by incorporating the principles of photonics in the nano-cantilevers, they had been able to boost the sensitivity of an average array to 0.0001 Angstroms, which is the equivalent of one ten thousandth of the size of an atom.

Tiny structures known as cantilevers are the most fundamental mechanical sensors, in a class of devices called nanoelectromechanical systems (NEMS). They are attached at one end to the array, while the other one is free. When a certain type of molecules hits them, they deform to some extent. This movement can be detected, transformed into electrical current, and then fed in to a computer software, which in turns determines what it is. However, this type of sensor arrays has been never before so sensitive.

The new sensor multiplexes are built inside a photonic wire, and each of them has up to ten nano-cantilevers inside. Light moves inside the wire and excites one or more of the cantilevers. Because they are disposed a bit offset from each other, they each generate a certain “tone,” which can be traced and recorded. “Detecting the lightwave after this evanescent tunneling gives the unprecedented sensitivity,” Tang said.

“We don't need a laser to operate these devices. Very cheap LEDs will suffice,” paper co-author Wolfram Pernice shared. “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,” Tang concluded.