In this work, properties of both microinjection molded (MIM) and conventional injection molded (CIM) samples were investigated. Results showed that the difference in thermomechanical history between both processing methods leads to the formation of different microstructure in corresponding iPP/PET moldings. For example, the dispersed spherical PET phase deforms and emerges into continuous in-situ microfibrils due to the intensive shearing flow field and temperature field in MIM. Additionally, the incorporation of PET facilitates the laminar branching and reservation of oriented molecular chains, thereby leading to forming a typical hybrid structure (i.e. fan-shaped â-crystals and transcrystalline). Furthermore, more compact and higher degree of oriented structure can be obtained via increasing content of PET. Such hybrid structure leads to a remarkable enhancement of mechanical property in terms of MIM samples. This study provided a new approach to fabricating microdevices with enhanced mechanical properties.