Highly Transparent and Sensitive Graphene Sensors for Continuous and Non-invasive Intraocular Pressure Monitoring

Abstract

Intraocular pressure (IOP) is the prime indicator for the diagnosis and treatment of glaucoma. IOP has circadian rhythm changes and is dependent on body gestures; therefore, a single measurement in the clinic can be misleading for diagnosis. Herein, few-layer graphene is utilized to develop non-invasive sensors with high transparency, sensitivity, linearity, and biocompatibility for 24 h continuous IOP monitoring. The graphene Wheatstone bridge consisting of two strain gauges and two compensating resistors is designed to improve the sensitivity and accuracy of IOP measurement. Testing results on a silicone eyeball indicate that the output voltage of the sensor is proportional to the IOP fluctuation. Under the various ranges and speeds of IOP fluctuation, the sensor exhibits excellent performance of dynamic cycles and step responses with an average sensitivity of 150 μV/mmHg. With the linear relationship, the average relative error between the calibrated IOP and the standard pressure is maintained at about 5%. More than 100 cycles and interval time measurements illustrate that the sensor possesses significant stability, durability, and reliability. Furthermore, a wireless system is designed for the sensor to realize IOP monitoring using a mobile phone. This sensor, with the average transparency of 85% and its ease of fabrication, as well as its portability for continuous IOP monitoring, brings new promise to the diagnosis and treatment of glaucoma.

Materials, Electrical Performance, Mechanisms, Applications, and Manufacturing Approaches for Flexible Strain Sensors

“…Through depth research on graphene-based sound detection and sound emission, this sensitive sensor is very meaningful for helping mute people to “spear” in the future. For continuous and non-invasive intraocular pressure monitoring, by employ photolithography, CVD, and thermoforming methods, Ren et al fabricated a wireless monitoring system with 85% transparency for diagnosis and treatment of glaucoma [ 247 ]. Scalable fabrication of flexible electronics is essential in the future, for this purpose, Lin et al proposed an innovative design of 3D structures for flexible electronics sensor combined photolithography with screen printing technology, [ 248 ] which contains 25 × 25 array of sensing pads and bumps within 15 × 15 mm 2 area.…”

Wearable and Implantable Intraocular Pressure Biosensors: Recent Progress and Future Prospects

“…To accomplish portable IOP examination, a platform with Bluetooth module integrated on printed circuit board (PCB) was developed. [ 105 ] The IOP variation could be sampled by graphene‐based Wheatstone bridge (Figure 2c‐I), then transmitted by Bluetooth wirelessly (Figure 2c‐II). The contact lens sensors comprised of few‐layer graphene enable wearable electronics with highly transparent (Figure 2c‐III), soft (Figure 2c‐IV), sensitivity, and biocompatibility for 24 h continuous IOP monitoring.…”

“…The common models include porcine eye, [102,104,[109][110][111][112]132,145,146,182] bovine eyeball, [11] canine eye, [113] rat's eyeball, [36] rabbit eye, [37,103,197] and artificial silicon eye model. [42,105,145,198] These models offer feasibility and convenience for the developments of wearable IOP detectors. While, there are critical differences in cornea parameters of this models such as thickness, curvature, and elastic modulus.…”

An Ultrasensitive Contact Lens Sensor Based On Self‐Assembly Graphene For Continuous Intraocular Pressure Monitoring

“…The strain gauge is composed of metal films, which limit its sensitivity and transparency. Jiandong Xu et al [23] improved the contact lens sensor transparency by replacing metal gauges with few-layer graphene grown by chemical vapor deposition (CVD). The sensitivity of the IOP sensor is slightly improved to 150 µV mmHg -1 , however, the CVD growth continuous graphene film has a gauge factor (GF) of only 6.1 under 1% strain.…”