Abstract
The high cost and poor portability of external infrared thermal imagers have limited the widespread adoption of photothermal lateral flow immunoassays (PT-LFIAs) in on-site testing. To address this, we developed a smartphone-based handheld Thermal Contrast Amplification (TCA) Reader, eliminating the need for costly external hardware. Compared with existing recent external thermal imager-based PT-LFIA readout, this reader integrates a selected thermal-sensor-equipped smartphone, a motorized laser module, Bluetooth-enabled control, and a fixed 3D-printed holder into a compact device. The reader enables automated thermal signal acquisition with a same-strip measurement CV below 1% and supports multiple PT-LFIA formats. Using Au@Ag core-shell nanoparticles (Au@Ag NPs) as reliable photothermal labels, the handheld TCA reader-based PT-LFIAs (hT-PT-LFIAs) offers higher sensitivity compared to conventional LFIAs. The hT-PT-LFIAs can be used for the multiplex detection of viral antigens (Influenza A/B, SARS-CoV-2), small molecule drugs (morphine, methamphetamine, ketamine) and nucleic acids (HPV 16/18), demonstrating versatility across various LFIA formats, good clinical performance in training cohort, and high repeatability for small molecule assay. By seamlessly integrating micro-engineering, nanotechnology, and smartphone-based sensing, this work provides a low-cost, portable, and broadly applicable PT-LFIAs detection strategy that bridges a critical technological gap.