Real-time Measurement of Single Bacterium's Refractive Index Using Optofluidic Immersion Refractometry

This paper presents a biophysical method to characterize single bacterium in water by using an on-chip optofluidic immersion refractometer. Water safety is a major factor in the well-being of people, but the presence of bacteria such as Escherichia coli (E. coli), bacillus subtilis, Shigella flexneri and vibrio cholera in drinking water can lead to infectious diseases such as typhoid fever. Hence, it is crucial to detect and identify bacteria to prevent bacterial outbreaks. In this paper, an optofluidic immersion refractometer is developed to measure three biophysical parameters, i.e. size, shape and refractive index. The refractive index of a single bacterium is measured in high sensitivity of 0.005 RIU. This system is an innovative method to allow on-site real-time detection of single bacterium in water. It significantly reduces the amount of detection time and do not require trained personnel or additional chemical and biological reagents.