Accurate alignment system for photonic-based biosensor cartridges

Photonic biosensors for medical diagnostics have been in development for decades, demonstrating performance equal to or better than other techniques (e.g., ELISA, PCR) in sensitivity, reliability, and time efficiency. For companies to successfully commercialize these sensor products, they must also perform equal or better in price per test and usability. The price per test is largely determined by the costs of the (disposable) cartridge containing the sensor chip and bioactive layer. Eliminating active components from the cartridge can reduce costs but introduces the challenge of coupling light from a source to the sensor chip and back to detectors, particularly in point-of-care settings. This coupling requires a positioning accuracy in the (sub-) micrometer range. We present a proof-of-concept demonstrator system for point-of-care use that integrates a passive alignment step with an active alignment procedure. The passive alignment achieves high initial accuracy when a cartridge is placed in an acceptor slot, finding a “first light” state to enable active alignment. Active alignment fine-tunes the fiber position via actuators to optimize coupling efficiency. Optimal coupling is achieved within 30 seconds, yielding a Signal-to-Noise Ratio (SNR) of 36.5 dB. Repeatability tests with ten reinsertions of the same cartridge demonstrated passive alignment accuracy of 1.3 × 0.8 μm across the optical axis. The demonstrator system also enables testing the influence of key parameters like the production accuracy of the cartridges on the initial alignment. The resulting system has shown to comply with the requirements of ease of alignment along with full automation.