Geometric Replication Integrity of Micro Features Fabricated Using Variotherm Assisted Micro Injection Moulding

Abstract

The geometric surface integrity of micro patterns is critical for functionality of polymeric micro devices, e.g. replication accuracy for micro channels and individual lens for the element of a compound eye lens. Micro injection moulding has been used widely for mass production of these devices. However, achieving high replication integrity is a critical challenge. In the present work, we developed a variotherm assisted micro injection moulding process to replicate a micro droplet and ellipse feature arrays in order to study the deformation behaviour of sickled blood cells. The effects of warm circuit temperature and cold circuit temperature on replication integrity, including filling depth, profile and morphology, were characterized based on moulding process monitoring, measurement and imaging. We have found that the warm circuit temperature is critical for feature filling due to its influence on the polymer-mould interface temperature, and that too high a warm circuit temperature can cause significant adhesion of polymer to a micro cavity. The cold circuit temperature controls shrinkage of polymer melts and the mould, and subsequently influences demoulding. Both temperatures need to be optimized to achieve the best replication of micro features.