Early-stage disease diagnosis relies on the highly sensitive detection of biomarkers, such as optical whispering-gallery-mode (WGM) microcavity sensors; such devices provide precise, label-free biosensing. However, scaling and integrating large-scale arrayed WGM microcavity sensors is challenging. Bottlenecks in sensor design can lead to these bottlenecks. In response, researchers at Hong Kong Polytechnic University developed a 3D micro-printed WGM micro-laser sensor for sensitive on-chip biosensing. The developed sensor, a limacon-shaped WGM micro-laser sensor, was created using flexible micro-printing technology with the optical advantages of WGM micro-lasers. Hong Kong Polytechnic University researchers developed a 3D microprinted biosensor. The device supports the development of optofluidic biochips for rapid, quantitative, and simultaneous detection of multiple disease biomarkers.Courtesy of Hong Kong Polytechnic University. In the device, optical WGM micro-laser sensors circulate light resonantly within tiny microcavities. Experimental results highlighted the potential of the device for ultralow-limit detection of biomarkers in early disease diagnosis. When target molecules bind to the cavity’s surface, they induce slight changes in the laser’s wavelength, enabling highly sensitive detection of biological substances. “In the future, these WGM micro-laser sensors could be integrated into a microfluidic chip to enable a new generation of lab-on-a-chip devices for ultrasensitive, quantitative detection of multiple biomarkers," said research lead A. Ping Zhang. "This technology could be used for the early diagnosis of diseases such as cancers and Alzheimer's disease, or for fighting major health crises such as the COVID-19 pandemic.” The challenge in scaling these sensors is the need to couple light entering and leaving them, which typically requires a tapered optical fiber with a diameter WGM microcavity sensors have emerged as a highly promising technology for precise, label-free biosensing. Courtesy of Hong Kong Polytechnic University. The sensor, using resonance and a narrow linewidth of lasing peaks, can detect immunoglobulin G, an extremely small but common antibody found in blood and other body fluids. Experimental results showed that the sensor can detect this antibody at a detection limit of ~70 ag/mL. Integrating the micro-laser sensors into a microfluidic chip could lead to the eventually development of optofluidic biochips for rapid, quantitative, and simultaneous detection of multiple disease biomarkers. This research was published in Optics Letters, (www.doi.org/10.1364/OL.557384).