Replication of micrometric and sub-micrometric structured surfaces using micro-injection and micro-injection compression moulding

In the work reported, mu-IM and mu-ICM using replaceable silicon mould inserts were utilized for prototyping test structures with micrometric and sub-micrometric feature size in thermoplastic polymers (polypropylene and cyclic olefin copolymer). The mould inserts were manufactured using clean room technologies. The combination of mould insert and mould holder allowed temperature control and vacuum application. Replication was realized using electrical commercially available mu-IM/mu-ICM equipment. In particular, the replication at the micrometric and sub-micrometric scales has been explored. Material characterization was conducted to estimate the Cross-WLF viscosity model parameters using a nonlinear least square method. A 3D-thermal study of the heat transfer inside the mould was developed on Comsol Multiphysics to simulate the thermal distribution over the contact surface between mould and mould insert in the mu-IM process. Finally, replication results were analyzed and discussed. Obtained results at microscale show high fidelity between the moulded parts and the mould. The mu-ICM shows better results than mu-IM at the sub-micrometric scale, as the fidelity increased.