Faster temperature control systems for hot embossing and injection molding

Research work aims to develop a fast, production suitable hot embossing technology including appropriate tool systems for low-cost and production-integrated manufacturing of high-precision microfluidic structures in polymer films. The implementation is demonstrated by structuring of microfluidic films for disposable diagnostic devices used in home-care and point-of-care applications. The approach focuses on the development and thermal design of a tool system for fast hot embossing on basis of a fast non isothermal process. Close contour tempering of the active parts is the core of this approach. Based on an industrial specification the paper will describe tempering strategy, design and simulation of the tool concept. Heat flux and heat capacities together with the power loss in the system are used for calculating the tempering cycle. Based on that, the setup of an optimized tool system consisting of heating elements and a refrigerant system is presented. The new tool concept is thermally characterized by thermocouple and infrared measurements. Furthermore the system was tested in a commercial hot embossing equipment to demonstrate the improvements. It could be shown that a cycle time between one and two minutes is possible, in comparison to cycle times of fifteen minutes in conventional hot embossing systems. Although the test system was not optimized so far, in the embossing tests all items were replicated correctly and the microfluidic function was ensured. The results of the research work are applicable also for the optimization of injection molding tool systems