Determining refractive index of single living cell using an integrated microchip

We report a novel method for measuring the effective refractive index (RI) of single living cell using a small integrated chip, which might be an efficient approach for diseases diagnosis. This microchip is able to determine the refractive index of single living cell in real time without any extra cell treatments such as fluorescence labelling, chemical modification and so forth, meanwhile, providing low cost, small size, easy operation and high accuracy. The measurement system integrates an external cavity laser, a microlens, and some microfluidic channels onto a monolithic chip. In the experiments, two standard polystyrene beads with nominal RI are utilized to calibrate the measurement system and five different types of cancerous cells are subsequently measured in the chip. The experimental results show that the refractive indices of the cancerous cells tested ranges from 1.392 to 1.401, which is larger than typical value of normal cell of 1.35-1.37. This integrated chip potentially has a serial of applications on biodefense, disease diagnosis, biomedical and biochemical analysis.