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Kun Huang, Jeong O Lee, Christopher F Divsalar, Trong T Nguyen, David W Sretavan, Hyuck Choo, ; Nanophotonics-based Intraocular Pressure (IOP) Sensor with Remote Optical Readout. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2167.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a miniaturized nanophotnonics-based implantable device for frequent, automated remote monitoring of IOP.
The basic nanophotonics IOP sensor consists of a sealed cylindrical chamber, with gold nanodot arrays on flexible membranes forming the top & bottom chamber surfaces (Fig. 1 A). When interrogated with light, the reflected signal from the device shows maximal reflectance dips at specific wavelengths, and is the spectral signature of a unique gap size between nanodot arrays. Within the anterior chamber, the nanodot membranes deform as the ambient pressure, i.e. IOP rises, causing the gap between arrays to decrease (Fig. 1 B). This gap narrowing causes the reflectance spectrum to shift (Fig. 1 C, D), and is detected remotely via a spectrometer.
Proof of concept devices were fabricated consisting of two thin rigid glass substrates containing gold nanodot arrays, separated from each other by ~6 μm-thick photoresist (Fig. 2 A). 5 devices with gaps of 6.32, 6.38, 6.45, 6.51, and 6.60 μm were interrogated and the reflected signal analyzed using a spectrometer. The reflectance spectra showed a systematic shift in the reflectance dip maxima with increasing gap separation (Fig. 2 B), in agreement with predictions from simulation. Prototypes were also implanted into rabbit eyes ex vivo (Fig. 2 C, D). A reflectance spectrum with identifiable reflectance dips was detected remotely at 7 mm from the nanodot arrays (Fig. 2 F).
A nanophotonics-based method of IOP sensing is in principle viable. Advantages of this approach include potential miniaturization to obtain 25-50 μm devices and remote sensing using light ultimately at a distance of 5 cm or larger.
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