Multi-spectral fluorescence microscopy with embedded liquid filters for point-of-care applications

We present a new way of multi-spectral fluorescence microscopy using the embedded liquid filters in a microfluidic chip, providing flexibility of filter changes for target fluorescence wavelengths and low-cost assays for point-of-care (POC) applications. Widely available food color solutions are adopted for emission filter to absorb residual excitation light. Absorbance of the microfluidic liquid filter was measured for various dye concentrations and filter layer thicknesses. Also, absorbance spectrum of two different color mixtures was investigated for tuning the filter wavelength. Both results match with theoretical Beer-Lambert Law. On-chip liquid-filter fluorescence imaging was demonstrated with multiple LED light sources and fluorophores. Live (green)/dead (red) fluorescence images of C6 cells viability assays were successfully demonstrated using the fabricated microchip with the embedded liquid filters. The images taken with the liquid filter were comparable to those from the conventional microscope using FITC HYQ and TRITC HYQ filter sets.