3D micro-printed polymer limacon-shaped whispering-gallery-mode microlaser sensors for label-free biodetection

Optical whispering-gallery-mode (WGM) microlaser sensors have garnered significant attention in biological sensing due to their distinct advantages, including strong light–matter interactions and versatile sensing modalities. However, challenges remain in developing WGM microlaser sensors that can serve as building blocks for large-scale integrated sensor platforms in lab-on-chip applications. In this work, we present a 3D micro-printed polymer limacon-shaped WGM microlaser sensor for on-chip integrated biosensing. The WGM microlaser sensor has both high-quality factor (Q factor) and directional emission properties, making it ideal for high-sensitive on-chip biosensing platforms using a far-field coupling scheme. Experimental results showed that the 3D micro-printed WGM laser sensor has a very low lasing threshold of 3.87 µJ/mm² and a narrow lasing linewidth of about 30 pm. Remarkably, experiments have shown that the sensor can detect human IgG with a detection limit of around 70 ag/mL, revealing its potential for ultralow-limit detection of biomarkers in early disease diagnosis.