Near‐Field Communication Powered Hydrogel‐Based Smart Contact Lens

Abstract

handling into the eye. The cornea, which is the environment where the CL is worn, is the first layer of the eye to which we have direct access and plays an important role in monitoring the health of the ocular surface. A soft contact lens with graphenebased electrodes has been demonstrated to perform local electroretinogram which can monitor in real time the electrophysiology of the corneal surface. [8] Although, this device was tested in animal models, optical power correction (found in conventional contact lenses) was not included. Additionally, the parylene support layer in direct contact with the eye lid could introduce discomfort while blinking (since parylene is commonly known as hydrophobic). [9,10] Tear fluid, originated at the lacrimal gland and drained by the lacrimal ducts, [11] covers the corneal surface (for protection and moist) allowing the CL to float and at the same time to have a direct interaction with its physiology. [12] This thin fluid layer, divided in lipid (outer), aqueous (middle) and mucin (inner) containing all the physiologically active substances present in blood, [13] is commonly known as colorless and transparent blood. Different studies have been reported on the elucidation of the causal relationship between the presence (quantity/ frequency) of certain biomarkers (e.g., cancer biomarkers) and systemic diseases. [14,15] With this in mind, attempts to monitor the differentiation and abnormalities of systemic diseases have been actively researched in recent years by introducing a system capable of measuring a specific substance from within a contact lens, [16-20] or measuring a physical quantity (i.e., temperature, pressure, etc.). [21,22] Regarding biosensors focused on the tear fluid, different approaches have been demonstrated either embedded inside of a contact lens [4,23] or by means of an external device temporarily in contact with the tears. These techniques aim to develop noninvasive and continuous monitoring solutions. Although not inside a contact lens, a flexible and biocompatible amperometric glucose sensor in contact with the eye and with an external readout system was tested in animal models and compared with glucose levels measured in blood. [24] The results show a delay between 40 to 60 min after the oral administration of glucose, which could present a risk factor for patients in need of reliable and fast glucose measurements. In parallel, a glucose sensor Nowadays, smart contact lenses (SCLs) display interesting features for healthcare monitoring; however, their comfort and practical usability strongly depend on the outermost material in contact with the eye. In this publication, the embedding of a custom-made and thermoformed Near-Field Communication based circuit in a conventional soft CL is presented. The circuit is composed of gold tracks on polyimide between thermoplastic polyurethane layers (insert), while the lens is based on industry standard double-molding process of poly(2-hydroxyethyl methacrylate) with proven compatibility with corneal tissue. The lens ...

Lab‐on‐a‐Contact Lens: Recent Advances and Future Opportunities in Diagnostics and Therapeutics

“…[ 319–321 ] Similarly, current data transfer techniques are bottlenecked in reducing power consumption, increasing the data transfer rate, and extending the working/communication distance. [ 319,322 ] In recent years, researchers from different fields have worked to solve these challenges to make the SCL wearable platforms more practical. [ 184,319,323 ] In this section, we provide discussions about the applicable powering techniques for SCLs, such as radio‐frequency identification, wearable batteries, and solar cells.…”

“…Besides, investigators have been optimizing the RFID‐like SCLs to improve biocompatibility, comfort, and functionalities. [ 15,322,341,342 ] Recently, an innovative soft SCL platform was developed with high transparency along with the integration of strain sensors, wireless antennas, stretchable interconnections, and the ASIC chips, as shown in Figure 12g. [ 96 ] The reinforced ring could transfer the overall strain variations through the rigid regime to the small elastic regime, which can then be detected by the Si strain sensor and acquired by the ASIC chip.…”

“…If the conventional gold pad was used for the ASIC chip, flip‐chip bonding could be a better approach. [ 15,322,341,342 ] The soft substrate placed more stringent requirements regarding the stretchability of the conductive materials. For example, nanomaterial conductive networks or serpentine paths could be used to address this issue.…”

Recent advances in materials and applications for bioelectronic and biorobotic systems

“…Similarly, several groups have successfully demonstrated the efficacy of smart contact lenses for monitoring of temperature, glucose content of tears, and other physiological information (Figure 7B). 9,57,58 Usage of smart contact lenses eliminates the need for expensive diagnostic devices, such as tonometers, and allows for noninvasive blood sugar monitoring (for diabetic patients). In the future, biomedical electronics will likely increase our ability to identify early signs of disease/illness and result in more comprehensive health data collection.…”

“…(B) Electronic circuit insert and assembly of smart contact lenses for near‐field wireless biomedical sensing. Reproduced with permission from Vásquez Quintero et al 58 . Copyright 2020, Wiley.…”