Biological Detection Based on the Transmitted Light Image From a Porous Silicon Microcavity

To realize rapid biological detection and real-time analysis, a porous silicon microcavity optical biosensor with a central wavelength of 1550 nm was designed in this study, and a detection method based on the change in the gray value of the transmitted light image was proposed. The proposed method uses a near-infrared laser at the low absorption band of porous silicon as the light source. The infrared light transmitted from the surface of the porous silicon microcavity is converted into visible light by the infrared upconversion card. The transmitted light image is recorded by the charge-coupled device, and the gray value of the image is calculated to achieve detection. The experimental results show a linear relationship between the change in the gray value and the increase in complementary DNA concentration. The limit of detection of the proposed method is approximately 4 nM. The proposed method is lable free and spectrometer free, achieves fast detection speed, and can be further applied to biological detection in porous silicon microarrays.