Design And Application Of Integrated Microfluidic Chip For Phase Change Detection In Microscale

In this paper, the methods of integrating the temperature control component and optical components with microfluidic chip were developed. We designed and fabricated the microfluidic chip which integrated with micro thermoelectric (TE) unit, optical fiber and prism. The quasi three-dimensional (3D) optical observation experiments of flow and phase change (PC) in microscale were completed. The main contents are as following:The mathematical models of fluid flow were established, the stress states of micro-particles in micro-fluid were analyzed, and the equations of PC principal were established. On this basis, the numerical simulations of PC and flow of fluid/micro-particles in microchannel were accomplished using the CFDRC fluid calculation software.We designed an observation method which can be used to observe the microchannel in side-view direction. The fluid flow in vertical direction was observed using this observation method. Based on the analysis of experimental data, the quasi 3D optical observation method was presented.We designed the quasi 3D optical observation method. This method was based on the microfluidic chip which integrated with micro TE unit, optical fibers and right angle prisms: the TE unit was used to cooling and heating the fluid; the optical fibers were inserted into microfluidic chip in order to import the excitation light; the prisms were inserted into microfluidic chip to reflect light that emitted from microchannel for vertical imaging.The microfluidic chips were fabricated:the molds were fabricated through micro-machining and microassembly technology; the PDMS chips were fabricated through molding method; the alignment of base-chip and cover-chip was completed by microassembly method; the prisms and optical fibers were inserted into microchip by two auxiliary devices for the purpose of detachable and reusable.We completed the quasi 3D optical observation of fluid flow and PC in microchannel, and researched the flow of micro-particles in microchannel during the operating process of PC valve. The experimental results showed that:the reflux existed in solidification and melting process because of the change of volume, which occurred in upstream of the PC valve during solidification process and downstream of the PC valve during melting process; the deposition phenomenon of the micro-particles in microchannel was observed; the lowest temperature of micro TE unit's cold junction can reduced to -20.7℃.