One of the most perplexing problems in nanotechnology is finding an efficient and precise way to build and machine the tiny devices.
Currently, there is no easy way to machine a wide variety of materials on the nanometer scale, Hunt said, and the technique with capabilities closest to the ultrafast laser is electron beam lithography. Even this approach does not allow machining below the surface or within a material.
Photolithography, the technique currently used to make computer chips, is used to do such machining on a larger scale but is difficult to get to the nanometer scale, requires specific materials and can generally only be used on one plane. For example, that means that channels on a chip cannot cross without mixing, placing a severe constraint on the microfluidics and “lab on a chip” designs.
But the unique physics of the femtosecond pulse allows machining in 3-D, Hunt said.
The unique physics of an ultra-short pulsed laser used at a very high intensity make it possible to selectively ablate or cut away features as small as 20 nanometers, Hunt said. This is possible because of the unique physics of how extremely short pulses of light interact with matter; specifically using femtosecond pulses, a blast of light just a quadrillionth of a second long.
“If we have three channels on a plane, we can link the outer two without cutting into the center one, we can go down over and up, we can cut a U-shape,” Hunt said. “Not being constrained to one plane, the level of complexity that can be achieved is much greater.”
The research team included Hunt; Gerard Mourou, professor of electrical engineering and computer science; Ajit Joglekar, who recently completed his doctorate in biomedical engineering; Hsiao-hua Liu, a post doc at the Center for Ultrafast Optical Science; and Edgar Meyhofer, associate professor of biomedical engineering and mechanical engineering.