Researchers from North Carolina State University have developed a new low-cost lithography technique that can create three-dimensional (3D) nanostructures for biomedical, electronic, and photonic applications, replacing laborious stacking of two-dimensional (2D) patterns to create 3D structures.
“Our approach reduces the cost of nanolithography to the point where it could be done in your garage,” says Dr. Chih-Hao Chang, an assistant professor of mechanical and aerospace engineering at NC State and senior author of a paper on the work.
Most conventional lithography uses a variety of techniques to focus light on a photosensitive film to create 2D patterns. These techniques rely on specialized lenses, electron beams or lasers, all of which are extremely expensive. Other conventional techniques use mechanical probes, which are also costly.
To create 3D structures, the 2D patterns are essentially printed on top of each other. The NC State researchers took a different approach, using nanoscale polystyrene spheres. The nanospheres are transparent, but bend and scatter the light that passes through them in predictable ways, according to the angle that the light takes when it hits the nanosphere.
The researchers control the nanolithography (printing ultraminiature patterns) by altering the size of the nanosphere, the duration of light exposures, and the angle, wavelength and polarization of light. The researchers can also use one or multiple beams of light, allowing them to create a wide variety of nanostructure designs.
“We are using the nanosphere to shape the pattern of light, which gives us the ability to shape the resulting nanostructure in three dimensions without using the expensive equipment required by conventional techniques,” Chang says. “And it allows us to create 3D structures all at once, without having to make layer after layer of 2D patterns.”
The researchers have also shown that they can get the nanospheres to self-assemble in a regularly-spaced array, which in turn can be used to create a uniform pattern of 3D nanostructures.