Improvement of replication fidelity in injection moulding of nano structures using an induction heating system

In today’s industry, applications involving surface pattering with sub-μm scale structures have shown a high interest. The replication of these structures by injection molding leads to special requirements for the mold in order to ensure proper replication and an acceptable cycle time.
A tool insert with functional surface geometry in the sub-micrometer range was produced using aluminum anodization and subsequent nickel electroforming. For the complete replica of the pattern, elevated mold temperatures are required. For this purposea new mould set-up was developed, which allows rapid heating of the cavity wall by an induction heating system. The capability of the injection molding process to replicate the patterned surfaces into polycarbonate was investigated. Process optimization was carried out in terms of mold temperature/time variation and injection velocity. The replicated surfaces were quantitatively characterized by atomic force microscopy comparing the measurement in the nickel insert with the corresponding polymer nano-features. The experimental results show that the use of the induction heating system is an efficient way to improve the pattern replication.