The researchers used a laser to "write" the desired micrometer-sized lens shape out of a solution of bovine serum albumin, a protein. Methylene blue acts as a photosensitizer, which captures the light energy like an antenna and triggers a crosslinking reaction of the protein molecules. Driven by a computer, the laser cuts out the desired three-dimensional form voxel by voxel. A voxel is a three-dimensional pixel, a tiny segment of volume. The irradiation used is in femtosecond pulses, which lasts on the order of 10^-13 seconds. The crosslinking reaction only takes place in the locations that are irradiated. After the reaction, the protein molecules that have not reacted can simply be rinsed away. What stays behind is a cross-linked, aqueous protein gel in the shapes of micrometer-sized lenses.
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