The development of portable and easy-to-use instruments for accurate and rapid measurement of critical properties of micron size objects is urgently needed in the field of clinical diagnostics. Techniques based microfluidics and optics has shown tremendous potential for developing cost effective and portable instruments. In this work, we investigate the development of a micro flow analyzer that integrates microfluidics technology with optoelectronics for the detection of micro-particles and biological cells.

Cells in the range of 2-15 µm diameter, undergoing a focused laminar flow through a 150 µm wide micro channel are subjected to optical interrogation using lensed optical fibres. Resultant scatter signals indicative of the physical properties and fluorescence signals indicative of the biochemical properties are collected at specific angles using regular multimode optical fibres. The algorithm for data analysis built on Python has been used after proper validation on a simulated data set.

Unlike the conventional flow analyzer systems, here, the use of lensed optical fibres eliminates the need of additional light focusing components and adds compactness to the design. Developed prototype has been tested for the capability for distinguishing particles based on their size as well as the fluorescence intensity. Preliminary detection tests were optimized using standard polymer beads followed by mammalian live cells, and the results were compared with commercially available Guava easyCyte 8HT machine. The two methods, compared using a Bland-Altman plot, agree to within 95%.

In addition to the developed 2D flow focusing based microfluidic platform, droplet microfluidics is also employed to investigate encapsulated micro-particles. A technique to detect multiple fluorescence associated within a cell has been designed by the novel use of single laser and single detector. The delay in arrival time between individual fluorescence signals are used to identify multiple fluorescence. Such a multiplexed fluorescence detection system eliminates the need of multiple lasers and detectors being used in current systems and saves space and cost significantly.