Researchers at the Karlsruhe Institute of Technology (KIT) and Heidelberg University have developed a photoresist for two-photon microprinting that can be used to produce three-dimensional polymer microstructures with nano-sized cavities for the first time.
Photoresists are printing inks that can be used to 3D print the smallest microstructures in what is known as two-photon lithography. During printing, a laser beam is moved through the initially liquid photoresist in all spatial directions. The photoresist only hardens at the focal point of the laser beam. Gradually, complex microstructures can be built up. In a second step, a solvent washes out the areas that have not been exposed. What remains are complex polymer architectures on a micro- and nanometer scale.
With previous photoresists, it was not possible to print white material; only transparent, glass-like polymers could be produced. The new photoresist now makes it possible for the first time to print 3D microstructures from porous nanofoam, which has cavities between 30 and 100 nanometers in size that are filled with air. As in a porous eggshell, the numerous tiny air holes in the porous nano-architectures cause them to appear white.
