Designing a dual spectroscopic NIR/fluorescence probe for continuous medical screening - ULF-FORTH and ANT Ltd

Designing a fibre-optic-based illumination and signal collection head for nanodrop tensio-spectroscopy for ANT Ltd, a SME company based at Dublin, Ireland, focused on instrumentation for drop based tensiographic spectroscopy in the modalities of Raman, UV/Vis, fluorescence and Near IR for spectroscopic applications in forensics. ANT maintains a strong partnership with Starna Ltd UK, which is specialised in spectroscopic optics and standards.

An investigation was made into the implementation of a custom-made dual spectroscopic NIR and fluorescence optical fibre probe for continuous medical screening of human fluidic samples in the form of nano-volume drops. The optical-fibre-based module must be designed to handle nano-volume drops for simultaneous NIR and fluorescence spectroscopic measurements, while being manufacturable using standard optical components and processes. FORTH had undertaken the optical design from scratch of such a micro-optical module, using ray tracing and other beam propagation methods (such as FDTD) to fit the needs for NIR and fluorescence detection, while employing optical fibre light feeding and coupling components.  

ANT Ltd had limited experience with fibre optical devices, as well as with micro-optical instrumentation. Their need for a micro-optical unit to be readily implemented into their market-tested trensio-spetrophotometric systems was very strong, and approaches such as incorporating specialist optical components, which in turn would need significant adaptations of the original systems and devices, would be prohibitively expensive.

The FORTH-IESL team of the Photonic Materials and Devices Laboratory-PMDL ( designed a two-element optical enclosure based on standard parametric functional surfaces for performing light collection from a nanoliter liquid droplet, while using optical fibres for homogeneously exciting the droplet volume and collecting the emitted fluorescence at efficiencies greater than 30%. The optical design was developed to be readily manufactured using only standard CNC machining, relevant diamond tooling or 3D rapid prototyping, while using different materials and polishing protocols.

The initial project plan was to manufacture an operating prototype at STARNA UK and to perform the final optical testing of the component at FORTH while using broadband and laser sources and optical spectrum analysers operating within Laserlab-Europe; due to the COVID-19 pandemic these last manufacturing and testing steps were postponed.

The design developed by FORTH-IESL group was easily added to the relevant existing ANT Ltd designs, while boosting the light collection efficiency by a factor of 10x; these improvements were achieved through a small-sized optical design. Importantly, this new optical design can provide the fundamental light-collection performance for directing the light tension-spectroscopic devices of ANT Ltd in minimum-preparation, human fluidic samples, including into “hot topics” such as COVID-19 detection.

This industrial project was performed under the funding and auspices of the EU project H2020 ACTPHAST 4.0, coordinated by VUB, Belgium.

PMDL is a member of ACTPHAST 4.0 & ACTPHAST 4R consortia, and a frequent access provider to LaserLab Europe. PMDL through the ACTPHAST projects has provided/provides targeted photonic services and know-how to several Greek and EU companies and Institutions, in the areas of Renewable Energy, Smart Agriculture, Food and Beverages and Industrial Instrumentation. Further business/know-how cases of the areas above are available upon request.