Wearable Contact Lens Biosensors for Continuous Glucose Monitoring Using Smartphones

Abstract

Low-cost, robust, and reusable continuous glucose monitoring systems that can provide quantitative measurements at point-of-care settings is an unmet medical need. Optical glucose sensors require complex and time-consuming fabrication processes, and their readouts are not practical for quantitative analyses. Here, a wearable contact lens optical sensor was created for the continuous quantification of glucose at physiological conditions, simplifying the fabrication process and facilitating smartphone readouts. A photonic microstructure having a periodicity of 1.6 μm was printed on a glucose-selective hydrogel film functionalized with phenylboronic acid. Upon binding with glucose, the microstructure volume swelled, which modulated the periodicity constant. The resulting change in the Bragg diffraction modulated the space between zero- and first-order spots. A correlation was established between the periodicity constant and glucose concentration within 0–50 mM. The sensitivity of the sensor was 12 nm mM–1, and the saturation response time was less than 30 min. The sensor was integrated with commercial contact lenses and utilized for continuous glucose monitoring using smartphone camera readouts. The reflected power of the first-order diffraction was measured via a smartphone application and correlated to the glucose concentrations. A short response time of 3 s and a saturation time of 4 min was achieved in the continuous monitoring mode. Glucose-sensitive photonic microstructures may have applications in point-of-care continuous monitoring devices and diagnostics at home settings.

3D Printed Sugar‐Sensing Hydrogels

“…[ 6,8–10 ] Hydrogels of this nature also have the potential to improve upon currently available glucose‐monitoring systems via integration into flexible platforms, such as contact lenses or dermal sensing patches. [ 11,12 ]…”

Light‐Directed Soft Mass Migration for Micro/Nanophotonics

“…Thus far, much of the development of volume holographic colorimetric sensors has been mainly oriented toward improving the detection efficiency and expansion of detectable reagents . Currently, the translation of these foundational technologies into wearable and mobile devices (e.g., contact lenses and smartphones) is suggested as a future direction for their real‐world applications . Additionally, their relatively low diffraction efficiencies (generally less than 60%) need to be further improved for an enhancement in the structural color brightness …”

Contact Lens Technology: From Fundamentals to Applications

“…Cosmetic contact lenses, such as colored lenses and limbal‐ring lenses, are also popular, especially in Asian countries, and they are now classified as medical devices in the UK, US, China, Singapore, Malaysia, and Korea . Contact lenses were used as smart delivery systems to achieve extended drug releasing times, and as wearable biosensing platforms . On the other hand, contact lens wear was found to induce adverse effects, the most frequent being discomfort, microbial keratitis, allergies and corneal complications …”