Single-molecule detection by silicon-based photonic integrated circuits chip

The single-molecule detection technique plays a pivotal role in elucidating the fundamental mechanisms of various scientific processes at the molecular level, and holds essential importance in multiple fields including physics, biology, and chemistry. Recently, single-molecule detection has garnered increasing attention owing to its practical utility in medical diagnosis, primarily due to its exceptional sensitivity and the minimal sample volume required for analysis. However, the conventional single-molecule technique, represented by total internal reflection microscopy, faces challenges such as sophisticated operation procedures and limited detection throughput, thereby impeding its broader application. To address these limitations, we have demonstrated single-molecule detection using an integrated silicon photonic chip, offering a cost-effective and user-friendly alternative. By employing basic optics, we efficiently introduce the excitation source for single-molecule fluorescence by harnessing the strong evanescent field of high refractive-index waveguides. Subsequently, fluorescence signals are collected using basic optics comprising a water-immersion objective, relay optics, and a digital camera. Our results highlight a low-cost, high-throughput single-molecule technique achieved through the integrated silicon photonic chip. This innovative approach is promised to facilitate the widespread adoption of single-molecule fluorescence in medical diagnosis.