Early-stage disease diagnosis hinges on the sensitive detection of biomarkers, and researchers at The Hong Kong Polytechnic University (PolyU) have made a significant breakthrough in this field. By developing a novel 3D micro-printed whispering-gallery-mode (WGM) microlaser sensor, they aim to advance on-chip biosensing, facilitating the early detection of diseases.
Optical WGM microcavity sensors have emerged as a promising technology for precise, label-free biosensing. However, challenges in fabricating large-scale arrays and integrating them into lab-on-a-chip devices have hindered their widespread application. The PolyU team’s innovation addresses these issues, potentially transforming the landscape of biomedical diagnostics.
Innovative Sensor Design and Capabilities
Led by Prof. ZHANG -ping from PolyU’s Department of Electrical and Electronic Engineering, the research team has crafted a 3D micro-printed Limacon-shaped WGM microlaser sensor. This sensor combines flexible 3D micro-printing technology with the optical advantages of WGM microlasers, achieving superior biosensing performance and easier light coupling.
Prof. Zhang explained, “In the future, these WGM microlaser sensors could be integrated into microfluidic chips, enabling a new generation of lab-on-a-chip devices for ultrasensitive, quantitative detection of multiple biomarkers. This technology could be pivotal for early diagnosis of diseases such as cancers and Alzheimer’s disease, or in combating major health crises like the COVID-19 pandemic.”
Overcoming Integration Challenges
The newly developed microlaser sensor design overcomes the integration challenges that have historically impeded the use of such sensors in lab-on-a-chip systems for point-of-care diagnostics. The sensor’s resonant nature and narrow lasing linewidth allow for the detection of extremely small concentrations of biomarkers, such as human immunoglobulin G (IgG), a common antibody.
Experimental results showed that the sensor can detect human IgG at a detection limit of approximately 70 ag/mL, highlighting its potential for ultralow-limit detection of biomarkers in early disease diagnosis.
The research, titled “3D micro-printed polymer Limacon-shaped whispering-gallery-mode microlaser sensors for label-free biodetection,” has been published in Optics Letters and highlighted by the international optical society OPTICA.
State-of-the-Art Facilities and Future Directions
PolyU’s state-of-the-art facilities have been instrumental in supporting these groundbreaking innovations. Prof. Zhang noted, “This innovative microlaser sensor was made possible by our in-house 3D micro-printing technology, which allowed for the rapid fabrication of the specially designed 3D WGM microcavity and high-precision trimming of its suspended microdisk.”
Integrating photonic sensors onto a chip is crucial for advancing high-performance biosensing technology. Optical WGM microlaser sensors function by circulating light within tiny microcavities. When target molecules bind to the cavity’s surface, they cause slight changes in the laser’s wavelength, enabling highly sensitive detection.
Challenges and Solutions in Light Coupling
One of the main challenges in applying these sensors is the need for efficient light coupling, typically requiring a tapered optical fibre. These fibres are difficult to align and vulnerable to environmental disturbances, hindering real-time, high-sensitivity detection of biomolecules.
To address this, the research team designed a 3D WGM microlaser sensor with a Limacon-shaped suspended microdisk, offering low lasing threshold and directional light emission. This design improves light coupling efficiency, facilitating practical on-chip integration.
Experimental results demonstrated that the microlaser biosensors exhibited a very low lasing threshold of 3.87 μJ/mm2 and a narrow lasing linewidth of about 30 pm.
Moving forward, Prof. Zhang plans to integrate these microlaser sensors into microfluidic chips, developing optofluidic biochips for rapid, quantitative, and simultaneous detection of multiple disease biomarkers.
This development represents a significant step forward in the field of biosensing, with the potential to revolutionize early disease detection and improve global health outcomes.
