A plastic microchip the size of a fingernail could detect cancer DNA from a drop of blood in minutes, using a microwave signal instead of a bulky laser. Current genetic testing for lung cancer mutations takes weeks because samples must be sent to central labs. This project aims to shrink that process into a portable, low-cost sensor that a clinician could use at the patient’s bedside. The sensor is a polymer micro-ring resonator—a tiny loop of plastic that traps light and makes it highly sensitive to anything binding to its surface. The problem is that plastic resonators are less precise than silicon ones, and the usual readout requires expensive tuneable lasers. The researchers will solve both issues by using a microwave frequency sweep, modulated onto an optical carrier, to read the sensor’s response. They will also refine the nano-imprint fabrication process to improve the plastic rings’ quality. If successful, the platform could detect circulating tumour DNA from non-small cell lung cancer patients rapidly enough to guide treatment decisions within a clinic visit, rather than weeks later. Beyond lung cancer, the same low-cost, portable sensor design could be adapted for other infectious diseases or environmental monitoring, where speed and affordability matter more than laboratory-grade precision.
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This project seeks to develop a high-sensitivity, low-cost sensor platform with a wide range of uses. To bring focus to the work, we will target for point-of-care bio-sensing, and specifically will use as an exemplar the detection of the circulating tumor DNA (ctDNA) due to the well matched requirements for ultra-high sensitivity, rapid results and portable system which cannot be currently addressed by other means. Optical micro-ring resonators hold great potential for sensing. Their ability to produce very high quality resonance with light circulating around a loop many times before being lost enables very high sensitivity between the circulating light and the external influences. However, as well as being highly sensitive this process is hard to control. To achieve the best sensitivity, the amount of light lost per circulation has to be extremely low, and can only be achieved with complex manufacturing processes. At the same time, the readout system typically relies on expensive and bulky tuneable wavelength lasers. We seek to overcome both problems using a combination of low-cost polymer (plastic) resonators and a readout scheme method where a microwave frequency sweep modulated on an optical carrier is used rather than an optical wavelength sweep. Typically the achieved tolerances of polymer waveguides are less good than other material systems (e.g. silicon) resulting in lower Q factors, we will overcome this by refining the nano imprint fabrication process and also leveraging the readout scheme which allows the signals used for the readout to be tailored to the specific imperfections of an individual micro-ring resonator. By overcoming the difficulties associated with the use of polymer micro-rings, we expect to realise many benefits. Polymers are low cost, and particularly well suited to functionalisation with biomolecules which do not stick well to other surfaces, so we expect to find a wide range of applications in healthcare diagnostics as well as wider sensing applications. Our ultimate aim within this project is to demonstrate the ability to detect low levels of ctDNA of actionable mutations in human subjects with non-small cell lung cancer. The use of genomic and molecular information is now standard in the treatment of lung cancer though routine testing still requires several weeks for the results to return to the ordering clinician. A rapid point of care detection and classification of ctDNA will accelerate this process and likely lead to improved patient outcomes
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