Intraocular pressure (IOP) is a key clinical parameter in glaucoma management. However, despite the potential utility of daily measurements of IOP in the context of disease management, the necessary tools are currently lacking, and IOP is typically measured only a few times a year. Here we report on a microscale implantable sensor that could provide convenient, accurate, ondemand IOP monitoring in the home environment. When excited by broadband near-infrared (NIR) light from a tungsten bulb, the sensor's optical cavity reflects a pressure-dependent resonance signature that can be converted to IOP. NIR light is minimally absorbed by tissue and is not perceived visually. The sensor's nanodot-enhanced cavity allows for a 3-5 cm readout distance with an average accuracy of 0.29 mm Hg over the range of 0-40 mm Hg. Sensors were mounted onto intraocular lenses or silicone haptics and secured inside the anterior chamber in New Zealand white rabbits. Implanted sensors provided continuous in vivo tracking of short-term transient IOP elevations and provided continuous measurements of IOP for up to 4.5 months.

Numerous living organisms possess biophotonic nanostructures that provide coloration and other diverse functions for survival. While such structures have been actively studied and replicated in the laboratory, it remains unclear whether they can be used for biomedical applications. Here we show a transparent photonic nanostructure inspired by the longtail glasswing (Chorinea faunus) butterfly and demonstrate its use in intraocular pressure (IOP) sensors in vivo. We exploit the phase separation between two immiscible polymers (poly(methyl methacrylate) and polystyrene) to form nanostructured features on top of a Si3N4 substrate. The membrane thus formed shows good angle-independent white light transmission, strong hydrophilicity and anti-biofouling properties that prevent adhesion of proteins, bacteria, and eukaryotic cells. We then developed a microscale implantable IOP sensor using our photonic membrane as an optomechanical sensing element. Finally, we performed in vivo testing on New Zealand white rabbits and show that our device reduces the mean IOP measurement variation compared to conventional rebound tonometry without signs of inflammation.

We developed titanium nitride (TiN) based nanoelectromechanical (NEM) switch with the smallest suspension air-gap thickness ever made to date by a “top-down” complementary metal-oxide semiconductor fabrication methods. Cantilever-type NEM switch with a 15-nm-thick suspension air gap and a 35-nm-thick TiN beam was successfully fabricated and characterized. The fabricated cantilever-type NEM switch showed an essentially zero off current, an abrupt switching with less than 3mV/decade, and an on/off current ratio exceeding 105 in air ambient. Also achieved was an endurance of over several hundreds of switching cycles under dc and ac biases in air ambient.

Diabetes mellitus is a chronic disease, and its management focuses on monitoring and lowering a patient's glucose level to prevent further complications. By tracking the glucose-induced shift in the surface-enhanced Raman-scattering (SERS) emission of mercaptophenylboronic acid (MPBA), we have demonstrated fast and continuous glucose sensing in the physiologically relevant range from 0.1 to 30 mM and verified the underlying mechanism using numerical simulations. Bonding of glucose on MPBA suppresses the "breathing" mode of MPBA at 1071 cm-1 and energizes the "constrained-bending" mode at 1084 cm-1 , causing the dominant peak to shift from 1071 cm-1 toward 1084 cm-1. The MPBA-glucose bonding is also reversible, allowing continuous tracking of ambient glucose concentrations, and the MPBA-coated substrates showed very stable performance over a 30-day period, making the approach promising for long-term continuous glucose monitoring. Using this Raman-mode constraining and miniaturized SERS implants, we also successfully demonstrated intraocular glucose measurements in six ex vivo rabbit eyes within ±0.5 mM of readings obtained using a commercial glucose sensor.

Nanowires are being actively explored as promising nanostructured materials for high performance flexible electronics, biochemical sensors, photonic applications, solar cells, and secondary batteries. In particular, ultralong (centimeter-long) nanowires are highly attractive from the perspective of electronic performance, device throughput (or productivity), and the possibility of novel applications. However, most previous works on ultralong nanowires have issues related to limited length, productivity, difficult alignment, and deploying onto the planar substrate complying with well-matured device fabrication technologies. Here, we demonstrate a highly ordered ultralong (up to 20 cm) nanowire array, with a diameter of 50 nm (aspect ratio of up to 4,000,000:1), in an unprecedented large (8 in.) scale (2,000,000 strands on a wafer). We first devised a perfectly connected ultralong nanograting master template on the whole area of an 8 in. substrate using a top-down approach, with a density equivalent to that achieved with e-beam lithography (100 nm). Using this large-area, ultralong, high-density nanograting template, we developed a fast and effective method for fabricating up to 20 cm long nanowire arrays on a plastic substrate, composed of metal, dielectric, oxide, and ferroelectric materials. As a suggestion of practical application, a prototype of a large-area aluminum wire grid polarizer was demonstrated.