A biosensor based on a thermal camera using infrared radiance as the signal probe.

Flexible-type signal probes and their detection methods are increasingly being applied in biosensors. Among these, temperature-based signal probes represent a novel research direction. These sensors convert immunoassay signals into temperature signals, which are then detected using a thermometer or thermal infrared reader. However, from a physical viewpoint, we know that the temperature measured directly using a thermal infrared camera is the infrared radiance temperature, which is proportional to both the true temperature and emissivity. Herein, we design a novel sensing method that uses infrared radiance rather than true temperature as the signal probe. We convert the immunoassay to an infrared radiation temperature measurement by controlling an aluminum plate in constant temperature whose infrared radiation temperature varied significantly with immunoassay-based the amount of the target. We then develop two readout systems: one is based on a scientific-grade infrared camera, and the other uses a smartphone-based thermal camera, which is more portable, flexible, and can be used as an in-pocket sensor. The sensors are verified via detecting exemplary biomarker human IgG, and show excellent quantitative model performances in 0-100 ng mL concentration range with the detection limit estimated as low as 0.54 ng mL. The excellent quantitative results demonstrate the powerful detection performance of this sensing method.