Nanophotonic, Battery-Free Sensor for Glaucoma Monitoring: Glaucoma, a leading cause of blindness, largely stems from elevated intraocular pressure (IOP). Current IOP monitoring techniques are imprecise, provide no long-term monitoring, and have difficult readouts. A Samsung/Caltech team will describe a highly miniaturized (500-μm diameter, 200-µm thick) optomechanical nanophotonic sensor implant for long-term, continuous, on-demand IOP monitoring. The battery-free IOP sensor is made of a flexible, spongy medical-grade silicone containing 3D photonic nanostructures, produced using a colloidal self-assembly process. It functions as a pressure-sensitive optical resonator with a sensitivity of 0.1 nm/mmHg, and delivers IOP readings when interrogated with invisible near-infrared (NIR) light. The researchers implanted eight sensors in the eyes of New Zealand white rabbits, and demonstrated dynamic and long-term changes of IOP in awake rabbits with average accuracy of 0.56 mm Hg over a range of 0–40 mm Hg. With sensor refinements and detector automation, it may become a viable choice for patient-initiated glaucoma management in the home environment. (Paper #14.6, “Nanophotonic Sensor Implants with 3D Hybrid Periodic-Amorphous Photonic Crystals for Wide-Angle Monitoring of Long-Term In-Vivo Intraocular Pressure,” R. Siddique et al, Samsung/Caltech)

The top figure shows the nanophotonic intraocular pressure (IOP) sensor implanted in the anterior chamber of the eye, and probed with NIR light, while the optomechanical operating principle of the sensor is shown below it.

The left set of images in the bottom row comprise a photograph of a completed device with a 500μm-diameter; SEM images show the hybrid periodic and amorphous nanopatterns and confirm the thickness of 200µm.

The right set of images in the bottom row show the sensor implanted in the eye of a rabbit at Day 7 and Day 195, with no signs of tissue buildup.