Tyndall achieves two world‑firsts in miniature photonics integration

Researchers at Ireland's Tyndall National Institute have announced a breakthrough in optically powered miniature devices, and predict that it will be put to use in biomedical and diagnostic applications.

As described in Optics Letters, the project explored how optical power delivery can enable devices to operate in remote or hard-to-access biological environments, where traditional electrical power sources are impractical and conventional photovoltaic methods are unreliable.

As proof of concept, Tyndall has developed a fully optically powered, chip-on-tip micro-camera endoscope with a 3.0 millimeter outer-diameter catheter, designed for minimally invasive surgical guidance and in vivo diagnosis.

The device exploits the power-over-fiber (PoF) principle, in which power is delivered optically through a multimode optical fiber and converted to electrical energy at the receiver by custom PV cells.

This architecture improves biocompatibility by eliminating distal electrical conductors, and enables a new class of optically powered miniaturized biomedical devices. In the Tyndall case a 808-nanometer source coupled into a 250-micron optical fiber was packaged into two 3D-printed modules, a back-end photovoltaic power module and a front-end micro-camera module, to create an optically powered micro-camera probe.

"Although PoF requires precise alignment between the optical fiber and PV cell to minimize optical losses, it benefits from the lightweight nature of optical fibers and their ability to support high-speed data transmission without electromagnetic interference," wrote the Tyndall team. "These characteristics make PoF particularly well-suited for power-intensive, miniaturized applications."

New areas of exploration for intraoperative diagnostics

Building on this integration breakthrough, Tyndall has also developed the first chip-on-tip fluorescence lifetime imaging (FLIM) micro-camera at an endoscopic scale, described in a further Optics Letters paper. This micro-camera has an external diameter of 4 millimeters and comprises a miniaturized 1-square-millimeter 128 × 120 SPAD array detector, integrated imaging optics and an optical fiber for excitation light delivery. 

Three different light sources were trialled with the device: 375 and 405 nanometer pulsed laser diodes and a pulsed supercontinuum laser.

"This addresses key challenges in photonics packaging, stray light suppression, electrical interfacing and compact optical design to enable time-resolved fluorescence imaging at clinically relevant scales," wrote the team.

In trials on unlabelled ex vivo sheep tissues, the new device recorded a distinct contrast in FLIM data from intestine and lung samples, with a mean lifetime of 2.7 nanoseconds for the former and 3.5 nanoseconds for the latter. Features below 30 microns in size were resolved. 

Bringing FLIM systems to the tip of an endoscope will open new areas of exploration for intraoperative diagnostics and surgical guidance, commented Tyndall, and this research represents a significant step in translating semiconductor and photonics research into clinically relevant technologies. 

"Having demonstrated fully optically powered operation in controlled environments, we are now focused on progressing towards pre-clinical and in vivo validation," commented Sanathana Konugolu Venkata Sekar, head of the FAST-BioPhotonics research group at Tyndall. "This transition is essential to proving real-world viability in complex biological environments."