Online segment detection by zero-order diffraction of inelastic scattered light for raman spectroscopy in a microfluidic device

Abstract

The application of microfluidic diagnostic systems is becoming more and more important for life sciences in general. Especially the development of 'lab on a chip' (LOC) systems with integrated optical detection units has been rising over the last few years, due to the applicability of such systems in point-of-care diagnostics in home care or field applications. Droplet-based microfluidic systems, where sample droplets are processed in microfluidic networks became a powerful platform for LOC technology. A promising approach concerning this field is for example microfluidic Raman spectroscopy. Raman spectroscopy is successfully carried out in a microfluidic device applying a liquid/liquid segmented flow, where analyte-containing droplets (ACD) are formed in a carrier fluid like e.g. oil. However the detection within this system is limited as information of both phases, ACD and carrier fluid, are collected and therefore the acquisition time for each spectrum is relatively small. An improvement can be achieved by employing a trigger system, which allows the measurement of only ACD and accordingly an increase of the integration time. The challenge of implementing a trigger is to maintain a setup, which is compact with regard to a point-of-care application and allows the detection of the inelastic scattered Raman light without additional attenuation. In this contribution a new approach for the implementation of a trigger in a prototype setup for microfluidic Raman measurements is introduced. The feasibility of ACD detection by measuring not just the first-order diffraction but also the zero-order diffraction of the inelastic scattered light will be demonstrated. © 2011 Springer-Verlag Berlin Heidelberg.