To grasp and move microscopic objects, such as bacteria and the components of living cells, scientists can harness the power of concentrated light to manipulate them without ever physically touching them.
Now, doctoral student Amr Saleh and Assistant Professor Jennifer Dionne, researchers at the Stanford School of Engineering, have designed an innovative light aperture that allows them to optically trap smaller objects than ever before potentially just a few atoms in size.
The process of optical trapping or optical tweezing, as it is often known involves sculpting a beam of light into a narrow point that produces a strong electromagnetic field. The beam attracts tiny objects and traps them in place, just like a pair of tweezers.
Unfortunately, there are natural limits to the technique. The process breaks down for objects significantly smaller than the wavelength of light. Therefore, optical tweezers cannot grasp super-small objects like individual proteins, which are only a couple of nanometers in diameter.
Saleh and Dionne have shown theoretically that light passed through their novel aperture would stably trap objects as small as 2 nanometers. The design was published in the journal Nano Letters, and Saleh is now building a working prototype of the microscopic device.
Agonies of scale
As a materials scientist, Jennifer Dionne imagined an optical tool that would help her precisely move molecular building blocks into new configurations. "Optical tweezers seemed like a really cool way of assembling new materials," she said. Dionne is the paper's senior author.
Unfortunately, existing optical tweezers are not adept at handling these tiny building blocks. "It's been a known for several decades that trapping nano-sized objects with light would be challenging," said Dionne.
The problem is inherent to the light beam itself. Optical trapping typically uses light in the visible s
|Contact: Andrew Myers|
Stanford School of Engineering