High-efficiency optical systems for interrogation of dermally-implanted sensors.

Ratiometric Luminescent microparticle sensors have been developed for sensing biochemical targets such as glucose in interstitial fluid, enabling use of dermal implants for on-demand monitoring. For these sensor systems to be deployed in vivo, a matched optoelectronic system for interrogation of dermally-implanted sensors was previously designed, constructed, and evaluated experimentally. During evaluation experiments, it revealed that the system efficiency was compromised by losses due to fiber connections, the entrance aperture, and the entrance slit of the spectrometer. In this work, two optimization methods were investigated to overcome photon loss at fiber connections and internal trade-off between resolution and input light power of the current spectrometer: 1) Replacement of the CCD spectrometer with a two-detector system, enabling extraction of key spectral information by integrating signals over two wavelength regions (reference and sensing emission peaks); and 2) Free-space coupling of the optical probe to a custom low-resolution spectrometer. Photon loss was evaluated by experiments and simulations, preliminary hardware of two-detector system was constructed, and optimization simulations were performed to explore conceptual feasibility of the free-space coupling custom-designed spectrometer.