In this study, we demonstrated a smart handset-based retroreflective optical biosensing and Android application package for point-of-care testing. Briefly, a sedimentation property of an optical probe and organized inverting steps of the microchip were systematically combined to acquire the wash-free immunoassay procedure on the smart handset. Also, the retroreflective optical signal can be registered on a miniaturized optical gadget with the help of Android application for image processing.
