to easy manufacturing of biomimetic surfaces, surfaces that mimic the properties of biological tissues, according to a team of Penn State researchers. [Pulsifer et al., Bioinspir. Biomim., (2010), 5, doi: 10.1088/1748-3182/5/3/036001]
"Bioreplication began about 2001 or 2002," said Akhlesh Lakhtakia, Godfrey Binder professor of engineering science and mechanics. "All the techniques currently available are not conducive to mass replications.
The group of scientists developed a method to create macroscale molds or dies that retain nanoscale features. "We needed an object large enough to manipulate that still had nanoscale features," said Lakhtakia.
The researchers chose blowfly eyes because they have potential application in the manufacture of solar cells. Blowflies have compound eyes that are roughly hemispherical; but within that half sphere, the surface is covered by macroscale hexagonal eyes with nanoscale features.
"These eyes are perfect for making solar cells because they would collect more sunlight from a larger area rather than just light that falls directly on a flat surface," said Lakhtakia. In order to work in a manufactured product, the surface needs to retain the overall design in sufficient detail.
The researchers used arrays of nine blowfly eyes coated with 250 nanometers of nickel. This initial template was then electroformed -- a method of electroplating -- to deposit nickel on the back to create a master template half a millimeter thick.
The master template can be used either as a die to stamp the pattern or as a mold. The intention is to use the master die/mold to produce not only daughter dies/molds, but to tile the templates so that they can imprint large areas. The researchers will probably expand their template to include 30 blowfly corneas.