Highly Sensitive Cell Concentration Detection by Resonant Optical Tunneling Effect

This paper presents an original design for a volume refractive index (RI) sensor for cell concentration detection based on the unique resonant optical tunneling effect (ROTE). In this design, the solution sample is introduced into the ROTE resonant cavity, whose reflection spectrum presents a large shift of its resonant dip in response to the tiny change of the solution RI. Performance calibration using the polystyrene particle solution indicates that the sensitivity is 19,000 nm/RIU and the total Q factor is 620. Experiments with hepatoma cells have obtained sensitivity values as high as 2.53 nm/(amol/ml) and a detection limit of 1.2 × 10⁵ cells/ml. Compared with previously reported optical cell sensors, this original work implements the ROTE mechanism for the first time and presents superior device performance. Thus, the proposed design has a high potential for use in biomedical applications, such as drug discovery, cell research, and medical diagnoses.