3D-ordered porous composite microparticles formed via substrate-free optical 3D lithography

This paper proposes a cutting-edge photolithography-based top-down approach to produce functional porous microparticles with three-dimensional (3D) periodic nanostructures. The developed fabrication process employs proximity-field nanopatterning (PnP), a representative optical 3D nanofabrication technique in which a new type of phase mask and exposure scheme have been introduced. In the modified PnP mode, where the photoresist is directly coated on the phase mask, a 3D nanostructured membrane detaches from the mask during the development process. The freestanding 3D nanostructured membrane is electromagnetically shredded through simple ultrasonication to produce a large amount of 3D-ordered porous microparticles. A Gaussian distribution of particle sizes with an average size of similar to 37 mu m can be obtained through an optimization of the sonication time. In addition, composite porous microparticles that exhibit exceptional magnetically responsive properties can be generated by incorporating iron oxide nanoparticles into the rinsing solution as nanofillers.