Detection of micro/nano-particle concentration using modulated light-emitting diode white light source

Micro/nano-particles have attracted much interest in many research fields due to their unique optical, electrical, and chemical properties. However, many of these particles disperse in solutions during storage or usage, making their actual concentration difficult to determine. We describe in this paper our work in using a visible light communication (VLC) system to measure the concentration of micro/nano-particles. The VLC system is based on white light-emitting diodes and operates in amplitude modulation mode. A microscope system is used to project a light source from the VLC system into a microfluidic chip so that some information of the micro/nano-particles in the microfluidic chip can be acquired by the VLC system. Because the size of the particles tested in our experiments is close to the wavelength of visible light, Mie light scattering theory is used to simulate the influence on the light by the micro/nano spheres. The simulation results indicate that there is an approximately linear relationship between the concentration and absorbance at lower concentrations and smaller particle diameters, which were validated by our experiments with polystyrene micro/nano-particles using the VLC system. In addition, the bit error rate (BER) of the VLC system is also shown to be useful in measuring the micro/nano particle concentrations.