Nano device can detect infinitely small forces

Engineers at University of California San Diego have developed a nano-sized optical fiber that can detect incredibly small forces such as those created by swimming bacteria, or the beating of heart muscle cells.

The device is around 100 times thinner than and can detect forces ten trillion times smaller than a newton and sound levels one thousand times below the limit of the human ear.

Study lead, Donald Sirbuly from the UC San Diego Jacobs School of Engineering said: “This work could open up new doors to track small interactions and changes that couldn’t be tracked before”.

Sirbuly believes the device could be used for detecting the presence and activity of a single bacterium; monitoring bonds forming and breaking; sensing changes in a cell’s mechanical behaviour that might signal it becoming cancerous or being attacked by a virus; or a mini stethoscope to monitor cellular acoustics in vivo.

Atomic force microscopes (AFMs) are instruments that can already detect small forces. The optical fiber developed by Sirbuly and colleagues is at least 10 times more sensitive than AFMs however.

The device is made from an extremely thin fiber, is coated with a thin layer of polymer and is studded with gold nanoparticles. The device works by having a beam of light sent down the fiber which analyses the light signals it sends out. The signals then indicate how much force or sound the fiber is picking up from the surrounding cells.

“We’re not just able to pick up these small forces and sounds, we can quantify them using this device. This is a new tool for high resolution nanomechanical probing.” Sirbuly said.

In the future, the researchers plan to use the nano fibers to measure bioactivity and the mechanical behaviour of single cells. Other applications include creating ultra-sensitive biological stethoscopes and tuning their acoustic response to develop new imaging techniques.   

The research is published in Nature Photonics.