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![Various electrical components of contact lenses for different applications. A) A contact lens sensor with a wireless powered circuit.[⁴⁴] B) Proposed smart contact lens system architecture. Reproduced with permission.[⁴⁴] Copyright 2017, MDPI. C) Contact lens sensor composed of a field‐effect sensor and antenna for wireless detection of glucose. Reproduced with permission.[¹⁹] Copyright 2017, Springer. D) The wireless chip and the sensor, which are mounted onto an electronic ring and then embedded into the contact lens. Reproduced with permission.[⁸³] Copyright 2014, Google X. E) Integrated RF‐powered contact lens. Reproduced with permission.[¹²] Copyright 2010, IEEE. F) Conceptual diagram of an active contact lens system with RF power transfer. Reproduced with permission.[⁴] Copyright 2012, IEEE. Solid‐State Circuits. G) Self‐powered contact lens, composed of (a) a biocathode, (b) an anode, (c) a glucose biosensor, (d) an interface chip, (e) a simple display, and (f ) an antenna (as a communicator for data transmission), based on chemical reactions with ascorbic acid in human lacrimal fluids. Reproduced with permission.[³] Copyright 2013, ACS.](publication/351348458/figure/fig1/AS:11431281179349820@1691189660291/Various-electrical-components-of-contact-lenses-for-different-applications-A-A-contact.png)
Various electrical components of contact lenses for different applications. A) A contact lens sensor with a wireless powered circuit.[⁴⁴] B) Proposed smart contact lens system architecture. Reproduced with permission.[⁴⁴] Copyright 2017, MDPI. C) Contact lens sensor composed of a field‐effect sensor and antenna for wireless detection of glucose. Reproduced with permission.[¹⁹] Copyright 2017, Springer. D) The wireless chip and the sensor, which are mounted onto an electronic ring and then embedded into the contact lens. Reproduced with permission.[⁸³] Copyright 2014, Google X. E) Integrated RF‐powered contact lens. Reproduced with permission.[¹²] Copyright 2010, IEEE. F) Conceptual diagram of an active contact lens system with RF power transfer. Reproduced with permission.[⁴] Copyright 2012, IEEE. Solid‐State Circuits. G) Self‐powered contact lens, composed of (a) a biocathode, (b) an anode, (c) a glucose biosensor, (d) an interface chip, (e) a simple display, and (f ) an antenna (as a communicator for data transmission), based on chemical reactions with ascorbic acid in human lacrimal fluids. Reproduced with permission.[³] Copyright 2013, ACS.
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Smart contact lenses have emerged as novel wearable devices. Due to their multifunctional biosensing capabilities and highly integrated performance, they provide a great platform for the diagnosis of eye diseases and the delivery of drugs. Herein, a brief history of the development of contact lenses is given. Then, the state‐of‐the‐art design and f...
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Citations
... 53 Tears are less prone to biofouling than saliva, ISF, and sweat; however, the difficulty of collecting tears remains a challenge. Contact lenses are commonly used as a platform for tear fluid analysis 54 and show great potential for use in the prevention, diagnosis, and treatment of eye-related infections. Similarly, analysis of stool samples in laboratory settings is excellent for the assessment of gut microbiota, monitoring probiotic bacteria, and diagnosing inflammatory bowel disease. ...
The silent pandemic of bacterial antimicrobial resistance is a leading cause of death worldwide, prolonging hospital stays and raising health-care costs. Poor incentives to develop novel pharmacological compounds and the misuse of antibiotics contribute to the bacterial antimicrobial resistance crisis. Therapeutic drug monitoring (TDM) based on blood analysis can help alleviate the emergence of bacterial antimicrobial resistance and effectively decreases the risk of toxic drug concentrations in patients' blood. Antibiotic tissue penetration can vary in patients who are critically or chronically ill and can potentially lead to treatment failure. Antibiotics such as β-lactams and glycopeptides are detectable in non-invasively collectable biofluids, such as sweat and exhaled breath. The emergence of wearable sensors enables easy access to these non-invasive biofluids, and thus a laboratory-independent analysis of various disease-associated biomarkers and drugs. In this Personal View, we introduce a three-level model for TDM of antibiotics to describe concentrations at the site of infection (SOI) by use of wearable sensors. Our model links blood-based drug measurement with the analysis of drug concentrations in non-invasively collectable biofluids stemming from the SOI to characterise drug concentrations at the SOI. Finally, we outline the necessary clinical and technical steps for the development of wearable sensing platforms for SOI applications.
... In other words, the CGM performs glucose measurement every 5 min approximately (depending on the manufacturer procedure), then, data are transmitted to a handset. AI analyzes the data in real time, while considering the patient's physiology, history, and data entries (meals or exercise), it is possible to determine the correct dose of insulin to administer [189,190]. This helps in optimizing and automatizing diabetes treatment while lowering the mental charge of the diabetes patients. ...
According to the latest statistics, more than 537 million people around the world struggle with diabetes and its adverse consequences. As well as acute risks of hypo- or hyper- glycemia, long-term vascular complications may occur, including coronary heart disease or stroke, as well as diabetic nephropathy leading to end-stage disease, neuropathy or retinopathy. Therefore, there is an urgent need to improve diabetes management to reduce the risk of complications but also to improve patient’s quality life. The impact of continuous glucose monitoring (CGM) is well recognized, in this regard. The current review aims at introducing the basic principles of glucose sensing, including electrochemical and optical detection, summarizing CGM technology, its requirements, advantages, and disadvantages. The role of CGM systems in the clinical diagnostics/personal testing, difficulties in their utilization, and recommendations are also discussed. In the end, challenges and prospects in future CGM systems are discussed and non-invasive, wearable glucose biosensors are introduced. Though the scope of this review is CGMs and provides information about medical issues and analytical principles, consideration of broader use will be critical in future if the right systems are to be selected for effective diabetes management.
Graphical Abstract
... Alongside the improvement on materials and fabrication techniques for cheaper production and viable large-scale applications for BIPVs, BAPVs, and VIPVs, there are other fields in which bio-inspired (s)TPVs could find future novel applications, like the aforementioned wearable devices, smart glasses, or even smart contact lenses with added functionalities like drug delivery and biosensing [65,66]. Further developments in the implementation of bio-inspired light-management strategies may also lead to improved performance of PV devices, as shown for example by Tsai et al. [67]. ...
There has been a surge in the interest for (semi)transparent photovoltaics (sTPVs) in recent years, since the more traditional, opaque, devices are not ideally suited for a variety of innovative applications spanning from smart and self-powered windows for buildings to those for vehicle integration. Additional requirements for these photovoltaic applications are a high conversion efficiency (despite the necessary compromise to achieve a degree of transparency) and an aesthetically pleasing design. One potential realm to explore in the attempt to meet such challenges is the biological world, where evolution has led to highly efficient and fascinating light-management structures. In this mini-review, we explore some of the biomimetic approaches that can be used to improve both transparent and semi-transparent photovoltaic cells, such as moth-eye inspired structures for improved performance and stability or tunable, coloured, and semi-transparent devices inspired by beetles’ cuticles. Lastly, we briefly discuss possible future developments for bio-inspired and potentially bio-compatible sTPVs.
... Among various wearable bioelectronics, smart contact lenses have attracted commercial attention for in-vivo health monitoring 14,23,24,[26][27][28][29][30] . Tears could serve as a convenient and noninvasive object to monitor the physiological conditions in human body which can be collected in the contact lens naturally and used to assess various biomarkers such as glucose, sodium ions, potassium ions [31][32][33] . Thus, a contact lens equipped with sensors provide a noninvasive sensing method to monitor metabolites from in tears. ...
Smart contact lens has drawn extensive research interests due to the noninvasive real-time detection of the human body to provide biomedical information for health management. However, it has been difficult to accurately measure the physiological signals in tears, and the use of external power source has also hindered the future applications. Here, we demonstrated an organic electrochemical transistor based multiplexed sensors self-powered by the organic solar cells (OSCs). The integrated device was fabricated via simple process including solution blade-coating and thermal evaporation. OSCs were optimized to provide optimal operation voltage for the sensors that exhibit semilog-linear response to the glucose and calcium ions in tear fluids without any peripheral circuits. The sensing signals can be transmitted to the laptop wirelessly through a near filed communication unit. This integrated self-powered multiplexed sensing device will provide real-time monitoring of the biomarkers in tears, prospected to be installed on the smart contact lens for the early detection and diagnosis of diabetes.
... The power transfer and data transmission methods suitable for artificial retinas are applicable to smart lens applications. Electronic sensors and actuators integrated into a contact lens, generally called Smart Lens [168], [169], have been attracting a lot of attention due to their convenience, ubiquity and noninvasiveness. Smart lenses have been proposed to measure intraocular pressures for glaucoma diagnosis and drug delivery [170], glucose levels in tears for diabetic diagnosis and therapy [171], lactic acid (lactate) for hypoxia and changes of physiological or pathological conditions [172], and cholesterol [173]. ...
Advances and updates in medical applications utilizing microwave techniques and technologies are reviewed in this paper. The article aims to provide an overview of enablers for microwave medical applications and their recent progress. The emphasis focuses on the applications of microwaves, in the following order, for 1) signal and data communication for implants and wearables through the human body, 2) electromagnetic energy transfer through tissues, 3) noninvasive, remote or
in situ
physical and biochemical sensing, and 4) therapeutic purposes by changing tissue properties with controlled thermal effects. For signal and data communication and wireless power transfer, implant and wearable applications are discussed in the categories of pacemakers, endoscopic capsules, brain interfaces, intraocular, cardiac and intracranial pressure sensors, neurostimulators, endoluminal implants, artificial retina, smart lenses, and cochlear implants. For noninvasive sensing, remote vital sign radar, biological cell probing, magnetic resonance and microwave imaging, biochemical, blood glucose, hydration and biomarker sensing applications are introduced. For therapeutic uses, the developments of microwave ablation, balloon angioplasty, and hyperthermia applications are reviewed. The scopes of this article mainly concentrate on the research and development efforts in the past 20 years. Recent review articles on specific topics are cited with accomplishment highlights and trends deliberated. At the end of this article, a brief history of the IEEE Microwave Theory and Techniques Society (MTT-S) Biological Effects and Medical Applications committee and the contributions by its members to the promotion and advancement of microwave technologies in medical fields are chronicled.
In today's health-conscious era, the demand for continuous and personalized health monitoring is at an all-time high. Wearable biosensors play a pivotal role in addressing individuals’ increasing concerns about their well-being by enabling continuous monitoring of vital signs, including blood pressure, glucose level, and temperature, alongside various other chemical analytes, offering a paradigm shift in health monitoring. These devices hold immense potential to make far-reaching changes in healthcare and empower individuals to take control of their well-being. These biosensors comprise two essential components: a bioreceptor for recognizing target analytes (such as enzymes, antibodies, nucleic acids, or cells) and a transducer that translates biorecognition events into measurable signals, employing electrochemical, optical, thermal, or piezoelectric monitoring mechanisms. They are categorized based on diagnostic biofluids, encompassing epidermal biosensors for sweat and interstitial fluid, ocular biosensors for tears, and oral cavity biosensors for saliva. Diverse materials give rise to biocompatible, biodegradable, and self-healing flexible sensors, playing a crucial role in their performance. Biocompatible materials, such as hydrogels and polymers, ensure safe and comfortable contact with the skin whereas biodegradable materials offer a sustainable solution, particularly for implantable devices. Meanwhile, self-healing materials enhance the durability and longevity of wearable biosensors. They are adaptable to various wearable platforms, such as contact lenses, wrist straps, patches, implants, tattoos, and garments. These platforms offer a range of advantages, including unobtrusive integration into daily routines, continuous monitoring capabilities, and personalized data collection. Recent progress highlights advancements in electrochemical and optical methods, conductive textiles, and flexible skin patches and the development of multiplexed sensing and fully integrated wearable sensors, which encompass power supply from a small-sized battery or energy harvesting devices for self-powering and wireless electronics for data processing and signal transmission, enhanced by artificial intelligence (AI) and machine learning (ML). AI and ML are transforming wearable biosensors into intelligent systems. AI algorithms can analyze sensor data to identify patterns, predict trends, and provide personalized health insights. ML models can be trained on large datasets to improve the accuracy of analyte detection and enable early disease detection. The flexibility and stretchability of these devices eliminate the need for bulky detection instruments, allowing for noninvasive compatibility with the human body. These properties allow for continuous monitoring of physiological parameters without discomfort or restriction of movement. The integration of microfluidic technologies into wearable biosensors holds immense potential for future advancements. Microfluidic devices can handle small volumes of fluids with high precision, enabling sensitive and selective analyte detection. This synergistic combination promises to revolutionize biosensing applications. Despite their remarkable progress, wearable biosensors continue to face challenges. Ensuring accuracy, reliability, and stability across diverse environmental conditions remains a critical area of research. Data security and privacy concerns also need to be addressed. Addressing these challenges will pave the way for their widespread adoption in personalized healthcare and preventive medicine. As research and development continue to refine these devices, wearable biosensors are poised to transform healthcare, enabling personalized medicine, early disease detection, and improved health outcomes.
On‐the‐eye microsystems such as smart contacts for vision correction, health monitoring, drug delivery, and displaying information represent a new emerging class of low‐profile (≤ 1 mm) wireless microsystems that conform to the curvature of the eyeball surface. The implementation of suitable low‐profile power sources for eye‐based microsystems on curved substrates is a major technical challenge addressed in this paper. The fabrication and characterization of a hybrid energy generation unit composed of a flexible silicon solar cell and eye‐blinking activated Mg–O 2 metal–air harvester capable of sustainably supplying electrical power to smart ocular devices are reported. The encapsulated photovoltaic device provides a DC output with a power density of 42.4 µW cm ⁻² and 2.5 mW cm ⁻² under indoor and outdoor lighting conditions, respectively. The eye‐blinking activated Mg–air harvester delivers pulsed power output with a maximum power density of 1.3 mW cm ⁻² . A power management circuit with an integrated 11 mF supercapacitor is used to convert the harvesters’ pulsed voltages to DC, boost up the voltages, and continuously deliver ≈150 µW at a stable 3.3 V DC output. Uniquely, in contrast to wireless power transfer, the power pack continuously generates electric power and does not require any type of external accessories for operation.
