Smartphone-Based Fully Automated Optofluidic Device with Laser Irradiation-Induced Image Whitening

Herein, we have developed a fully automated optofluidic device to execute enzyme-linked immunosorbent assay (ELISA) using an active 96-well hybrid lab-on-a-chip (LOC) device. To automate the solution loading into the reaction zone of the device and the post-assayed signal analysis, laser irradiation-induced image whitening was utilized with a smartphone-based optical platform. Two optical phenomena were utilized in our platform to detect the liquid in the reaction chamber using a smartphone. First, by Fresnel's equation, the refraction difference between air and water resulted in the intensity change of the reflected light from the reaction chamber. Therefore, when the liquid was entering into the reaction chamber, the intensity of the reflected light was changed. Second, when the light intensity increases, the smartphone-captured image whitens out due to saturation, even when the red color light was incident. Therefore, by measuring the RGB value of the smartphone image, the intensity changes by the liquid movement in the reaction chamber were successfully monitored. Our platform showed a low detection limit of 7.81 pg/mL for the detection of the NT-proBNP human cardiac biomarker with almost a half standard deviation, compared to the manually operated LOC-based ELISA. As a fully automated LOC adopting a conventional 96-well ELISA platform, we thus concluded that the developed platform can be widely applied for point-of-care clinical tests.