In a groundbreaking development, researchers at The Hong Kong Polytechnic University (PolyU) have unveiled a novel 3D micro-printed whispering-gallery-mode (WGM) microlaser sensor designed to advance on-chip biosensing technology. This innovation promises to enhance early-stage disease diagnosis by enabling ultrasensitive, label-free detection of biomarkers.
Early detection of diseases often hinges on identifying specific biomarkers with high sensitivity. WGM microcavity sensors have shown immense potential in this domain, yet challenges in their large-scale fabrication and integration into lab-on-a-chip devices have persisted. The PolyU team’s breakthrough addresses these issues, paving the way for next-generation biosensing applications.
Innovative Design and Capabilities
Led by Prof. ZHANG -ping from the Department of Electrical and Electronic Engineering, the PolyU team has developed a 3D micro-printed Limacon-shaped WGM microlaser sensor. This design leverages flexible 3D micro-printing technology to combine the optical advantages of WGM microlasers, resulting in easier light coupling and superior biosensing performance.
Prof. Zhang emphasized the potential impact of this technology, stating, “In the future, these WGM microlaser 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. 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.”
Overcoming Existing Challenges
The newly developed sensor addresses several challenges that have previously hindered the integration of WGM sensors into lab-on-a-chip systems. Its resonant nature and narrow linewidth of lasing peaks allow for the detection of extremely small concentrations of 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 findings, published in Optics Letters and highlighted by the international optical society OPTICA, underscore the significance of the PolyU team’s work. The state-of-the-art facilities at PolyU have been instrumental in supporting these innovations.
Technical Advancements and Future Prospects
Optical WGM microlaser sensors operate by circulating light within tiny microcavities. When target molecules bind to the cavity’s surface, they induce changes in the laser’s wavelength, enabling sensitive detection of biological substances. However, a key challenge has been the need for efficient light coupling, typically requiring delicate tapered optical fibres.
The PolyU team’s design circumvents this limitation by utilizing a Limacon-shaped suspended microdisk, which improves light coupling efficiency. This design allows for low lasing thresholds and directional light emission, crucial for practical on-chip integration.
Prof. Zhang and his team have successfully fabricated arrays of these sensors using their self-developed 3D micro-printing technology, achieving a low lasing threshold of 3.87 μJ/mm2 and a narrow lasing linewidth of about 30 pm. The sensors demonstrated the capability to detect IgG at concentrations as low as attograms per millilitre.
Moving forward, Prof. Zhang plans to integrate the microlaser sensors into a microfluidic chip to develop optofluidic biochips for rapid, quantitative, and simultaneous detection of multiple disease biomarkers.
This development represents a significant leap forward in the field of biosensing technology, with the potential to transform early disease detection and management. As researchers continue to refine these sensors and explore their applications, the future of medical diagnostics looks promisingly precise and accessible.
