Fabrication and integration of a new Micro Reactor Array for fluorescence analysis

Abstract

In all the biological application there is an increasing demand for low power and high resolution (spatial and temporal) acquisition systems for portable and low cost instruments. Among the many methods used for biological testing, optical detection is the most common. In particular, fluorescence lifetime imaging is an investigation tool of paramount importance in molecular biology and medicine [1-2]. In fact, any energy transfer between an excited molecule and its environment in a predictable way changes the fluorescence lifetime. Moreover, lifetime does not depend on the concentration of the chromophore. Typical examples are the mapping of cell parameters such as pH, ion concentrations or oxygen saturation by fluorescence quenching, or fluorescence resonance energy transfer (FRET) between different chromophores in the cell. The integration of detection modules with high sensitivity and signal to noise ratio in a microfluidics system is a key feature in a lab-on-a-chip. In this work we report the realization and integration of a microfabricated Micro Reactor Array (MRA) coupled to a Single Photon Avalanche Diode (SPAD) array for fluorescence-based analysis. The MRA can provide a number of reaction sites in the same chip that can be independently functionalized and monitored, allowing for a fast and all-on chip analysis. With respects to the state of the art [3-9], our approach focused on the realization of a fully integrated MEMS-based micro-reactors and optical detector arrays with reduced cross-talk among the reaction sites. In this aim, the micro-wells module and the SPAD-based detector have been realized separately and then assembled. This was possible, at packaging level, by carefully matching the designs of the detector with the dimensions of the wells and by providing the two systems of alignment markers