We demonstrate a compact interrogation method for resonance-based biosensors, based on an integrated photonic chip with an array of resonant-cavity enhanced photodetectors. Due to the high signal-to-noise ratio, wavelength shifts in the 10 pm range can be measured, orders of magnitude smaller than the sensor and interrogator linewidths. This approach allows the read-out of resonance-based optical biosensors with simple integrated components, potentially enabling compact and low-cost sensing systems for point-of-care diagnostics.
Fiber-tip sensors have been used extensively for measuring chemical and physical parameters. Particularly, multimode fibers (MMF) tip sensors have become attractive since they open the possibility of using simple light-emitting diodes. While common techniques to fabricate MM fiber-tip sensors are labor-intensive, we developed a simple and controllable method to transfer large-area nanophotonic structures to the fiber end-face by mechanical contact, without using glue or micromanipulator. As proof of concept, a 2D photonic crystal (PhC) was successfully transferred to the tip of a multimode fiber, and its response to changes in refractive index was characterized, obtaining a sensitivity of 244 nm/RIU.
Laser-based diagnostics and therapeutics show promise for many neurological disorders. However, the poor transparency of the cranial bone limits the spatial resolution and interaction depth that can be achieved with these technologies. We have recently demonstrated a new method to address this challenge in biomedical research through the use of a novel transparent cranial implant made from nanocrystalline yttria-stabilized zirconia (ncYSZ). In addition, we have also explored the use of optical clearing agents (OCAs) to achieve a local, reversible and temporal reduction of the scalp scattering prior light irradiation. Our results show that the transparent nc-YSZ implants coupled with the OCAs perform well in providing enhanced optical access to the brain tissue, without need for recurrent craniotomies or scalp removal.
In this work, we demonstrate an optical fiber biosensor based on Fabry-Perot (F-P) interferometers using polydimethylsiloxane (PDMS) as a support for bioactive lipids. The sensors are fabricated by dip-coating producing PDMS end-capped devices. For biosensing, the PDMS cap was functionalized with a previously characterized bioactive lipid antigen cocktail from Mycobacterium fortuitum, used as a surrogate source of antigens for tuberculosis diagnosis. The performance of the biosensor was evaluated upon monitoring the changes in the interference pattern associated to the interactions between the active lipids and the antibody-containing sera. Our results show that the proposed biosensor offers new and attractive possibilities for developing novel lipidomic analytical tools.
Optical brain imaging based on intrinsic signals has revealed new insights into functional brain activation imaging. The main obstacle to this approach is the highly scattering cranial bone over the cortex which hinders the observation of intrinsic optical signals. We have introduced a novel solution for this limitation by proposing a transparent cranial implant providing long-term optical access to the brain, which we call the Window to the Brain (WttB) implant. In this study, we evaluated the feasibility of the WttB implant for multi-wavelength intrinsic optical signal imaging of the brain.
We report on a novel fabrication technique for polymer based Fabry-Perot (F-P) optical fiber sensors. The F-P interferometers are based on microbubbles generated in the polymer by means of a microheater fiber probe. Upon inserting the probe and a cleaved single-mode fiber in a capillary tube containing the polymer, a microbubble can be readily generated which can serve as a reflective surface. A F-P cavity is thus formed by the microbubble and the single-mode fiber tip and temperature or strain deforming the bubble can be detected upon monitoring the FP resonances. The fabrication and performance of these devices as a temperature sensor is presented in this paper.
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