Smart Contact Lenses for the New Era of IoT: Integrated Biosensors, Circuits, and Human–Machine Interface Systems

Abstract

The circuit helps the sensors realize signal readout, conversion, transmission, and complex logic functions. [19][20][21] The human-machine interface (HMI) system plays the role of the application layer in the field of the IoT. [22][23][24] By presenting the sensor information to users in a simple and user-friendly interface, the HMI system enables a good user experience. [25,26] In particular, in the context of the coronavirus disease 2019 (COVID-19) pandemic, the use of smart electronic technology to achieve real-time and wireless interactive sensing is necessary. [27][28][29] Smart contact lenses (SCLs) have been employed for monitoring information regarding the eyes, including physical information (e.g., pressure and temperature) and chemical information (e.g., glucose, protein, and pH). [30][31][32][33][34] These physiological signals are closely related to human health. For example, excessive intraocular pressure (IOP) can induce glaucoma, [35] the abnormal temperature of the ocular surface can cause dry eye syndrome, [36] and excessive glucose in tears may predict diabetic retinopathy. [37] Non-invasive monitoring of human health by using SCLs will aid in better understanding of the physiological state of the eyes and even the body; subsequently, effective measures can be employed in a timely manner for the early prevention or treatment of certain diseases. As personal health information can be monitored in real-time by using SCLs, patients no longer need to go to the hospital or rely on large medical equipment. [38][39][40][41][42] Therefore, the development of SCL devices in view of the rapid advances in IoT technology is an important research topic.In this review, we focus on the latest progress and prospects of integrated biosensors, circuits, and HMI systems on SCLs under the background of the rapid development of the IoT technology, as shown in Figure 1. First, we discuss the integration of biosensors on SCLs for physiological information monitoring of the eyes, including IOP monitoring, corneal sensing, color signals sensing, tear pH monitoring, and glucose sensing. Next, we focus on wireless communication circuits integrated into SCLs, which have different functions, such as physiological signal sensing circuits, sensing circuits for disease treatment, and circuits for power supply. Furthermore, we summarize SCLs used in the HMI system. WhetherThe rapid development of the Internet of Things (IoT) technology endows some traditional devices with intelligent functions. Compared with traditional contact lenses used for correcting vision or beautifying the eyes, smart contact lenses (SCLs) are developed to monitor some physiological information of the eye. Sculls can be used to continuously monitor eye diseases noninvasively in real-time. As a personal electronic device, SCs can aid people in understanding their physical condition better without affecting their personal life. This review mainly discusses the development direction and problems associated with sculls from the perspective of the IoT. SCs c...

Smart Contact Lenses as Wearable Ophthalmic Devices for Disease Monitoring and Health Management

“…However, the use of these devices is associated with a significant reduction in signal quality, with amplitudes being reduced to those obtained using corneal electrodes due to the substantial distance from the cornea, thereby limiting the precise interpretation of the ERG signals. Recently, technological advances in transparent electrode materials, biosensors, and wireless modules have developed SCL that combined soft corneal electrodes and soft contact lenses for ERG detection. ,, These SCL offer many advantages. First, the electrodes with softness enhance the level of comfort by achieving conformal contact with the sensitive ocular structures during ERG recordings.…”

“…Recently, technological advances in transparent electrode materials, biosensors, and wireless modules have developed SCL that combined soft corneal electrodes and soft contact lenses for ERG detection. 377,383,384 These SCL offer soft, transparent graphene-based contact lens electrodes (GRACEs) and conducted ERG sensing from cynomolgus monkeys and rabbits, as shown in Figure 19b. 377 The GRACE devices offered superior conformal contact and tighter interface with the cornea (Figure 19c, left) compared to the conventional ERG jet electrodes (Figure 19c, right).…”

The Future of Vision: A Review of Electronic Contact Lenses Technology

“…73 Despite the fact that most of the work in the field of continuous health monitoring applications has utilized near-field communication (NFC) or inductive coupling for wireless powering and data transmission, the e-CLs have attracted a lot of attention. 74 In 2020, Vaśquez Quintero published an article about a custom-made NFC-based circuit that was embedded in a traditional soft CL. The circuit was made of Au tracks on polyimide and inserted between thermoplastic polyurethane (TPU) layers.…”

A Review of Thin Films Used in Smart Contact Lenses

“…[2a] Based on what has been achieved with other wearable devices such as skin patches that interact with body sweat, the following are some of the proven and potential capabilities of smart contact lenses due to their interaction with human tears and detection of its biomarkers: [4] 1) detecting lactate levels in tears, indicative of increasing stress; [5] a) potentially useful in detecting driver fatigue based on eye focus while driving; b) possibly usable in monitoring doctors' concentration when performing multiple surgeries one after the other; 2) indicating dangerous level of blood sugar in diabetic patients, as well as automatically releasing drugs in response to this; [6] and 3) detecting ailments such as allergies, dry eye syndrome, and degenerative diseases like keratoconus. [7] Furthermore, extensive studies have been made to develop their reliability, stability, and comfort to the eye. [1a] The distinction of smart contact lens (SCLs) from normal contact lenses, aside the "smart" appendage, lies in the incorporation of devices like sensors and thin-film electrolytes into them for functions which go beyond eye sight correction to include wireless control of external devices and health monitoring by detection of eye fluid compositional variations.…”

“…Based on what has been achieved with other wearable devices such as skin patches that interact with body sweat, the following are some of the proven and potential capabilities of smart contact lenses due to their interaction with human tears and detection of its biomarkers: [ 4 ] 1) detecting lactate levels in tears, indicative of increasing stress; [ 5 ] a) potentially useful in detecting driver fatigue based on eye focus while driving; b) possibly usable in monitoring doctors’ concentration when performing multiple surgeries one after the other; 2) indicating dangerous level of blood sugar in diabetic patients, as well as automatically releasing drugs in response to this; [ 6 ] and 3) detecting ailments such as allergies, dry eye syndrome, and degenerative diseases like keratoconus. [ 7 ]…”