Handling Nano-Objects Just Became Simpler Thanks To Nano-Tweezers
As scientists try to discover particles on a nanometer scale, there is a need to create tools that can be used to dissect matter into its smallest measure. Near-field optical tweezers are one such tool, allowing scientists to handle and manipulate matter at the smallest level. In a new study, researchers with the Institute of Photonic Sciences (ICFO) demonstrate how the tool can trap and manipulate nano-sized objects.
Romain Quidant, leader at ICFO of the Plasmon Nano-Optics research group, said that the technique "could revolutionize the field of nano-science since, for the first time, we have shown that it is possible to trap, 3D manipulate, and release a single nano-object without exerting any mechanical contact or other invasive action."
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The best way to understand nano-tweezers is to imagine an elephant trying to move a needle with its mighty hoof. A needle is infinitely smaller and it would be a massive effort for the elephant to move it. Similarly, consider the needle to be a single cell or a tiny object just a few nanometers in size, like a virus. Trapping and observing it becomes difficult due to two reasons. A conventional optical microscope is not capable of visualizing a single molecule or cell and conventional tweezers have far too many limitations to accurately grasp and manipulate a nano-sized object, according to a press release.
The original optical instrument was created by Bell Labs in the 1980s, and demonstrated its ability to trap and manipulate nano-structures using laser light, which involved focusing a laser beam through a lens on to a tiny spot. The spot subsequently creates an attractive force due to the light's intensity, and then traps the micron-sized object.
Although, optical tweezers have been very useful in the fields of biology and quantum optics their inability to trap objects smaller than a few hundreds of nanometers prompted the invention of plasmonics-based nano-tweezers. These tweezers are capable of trapping nano-scale objects such as proteins or nanoparticles without overheating and destroying them.
A few years ago, ICFO researchers demonstrated that, by focusing light on a very small gold nano-structure lying on a glass surface - which acts as a nano-lens - one can trap a specimen at the vicinity of the metal where the light is concentrated. This proof of concept was limited to demonstrate the mechanism, but did not enable any 3D manipulation needed for practical applications.
Now, the researchers have developed the device further by implementing the concept of plasmonic nano-tweezers at the end of a mobile optical fiber, nano-engineered with a bowtie-looking gold hole for light. Using this approach, they demonstrate trapping and 3D displacement of specimens as small as a few tens of nanometers using an extremely small, non-invasive laser intensity. The greatest advantage of this technique is that an optical fiber provides a simple and manageable way of both trapping and monitoring the nano-specimen outside the confines of a lab.
This technique can be used to great advantage in the field of medicine to understand the biological mechanisms behind the development of a disease, since it allows the manipulation of viruses, bacteria, living cells, organelles, and even strands of DNA in a noninvasive way. Its invention has also paved the way for future development of similar nano-devices.
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