Contour offset algorithm for precise patterning in two-photon polymerization

A contour offset algorithm (COA) has been developed to fabricate precise patterns easily in the range of several microns using a nano-replication printing (nRP) process, which employs two-photon polymerization. In this process, microscale patterns are fabricated by a voxel matrix scanning method that uses raster graphic data transformed from the two-tone (black and white) bitmap figure file. The raster data consist of two kinds of entities to control laser on/off; '1' for laser-on and '0' for laser-off. However, the replicated patterns did not precisely coincide with an initial design due to an intrinsic shortage of the nRP process: the fabricated patterns become generally larger than the designed shape. To solve the point at issue, the COA was proposed in this work: an outer-contour matrix of an initial design was reconstructed then, it was modified by the amounts of offset-ratio that can be calculated using the relation of a pattern size, a designed figure size, and a voxel size. The effectiveness of the proposed algorithm was evaluated through several examples with 200 nm resolution.