In-depth correlation analysis between tear glucose and blood glucose using a wireless smart contact lens.

Tears have emerged as a promising alternative to blood for diagnosing diabetes. Despite increasing attempts to measure tear glucose using smart contact lenses, the controversy surrounding the correlation between tear glucose and blood glucose still limits the clinical usage of tears. Herein, we present an in-depth investigation of the correlation between tear glucose and blood glucose using a wireless and soft smart contact lens for continuous monitoring of tear glucose. This smart contact lens is capable of quantitatively monitoring the tear glucose levels in basal tears excluding the effect of reflex tears which might weaken the relationship with blood glucose. Furthermore, this smart contact lens can provide an unprecedented level of continuous tear glucose data acquisition at sub-minute intervals. These advantages allow the precise estimation of lag time, enabling the establishment of the concept called 'personalized lag time'. This demonstration considers individual differences and is successfully applied to both non-diabetic and diabetic humans, as well as in animal models, resulting in a high correlation.

Real-time in vivo monitoring of intraocular pressure distribution in the anterior chamber and vitreous chamber for diagnosis of glaucoma.

Glaucoma causes irreversible vision loss due to optic nerve damage and retinal cell degeneration. Since high intraocular pressure (IOP) is a major risk factor for glaucoma development, accurate IOP measurement is crucial, especially intravitreal IOP affecting the optical nerve and cells. However, conventional methods have limits in selectively and directly detecting local retina pressure. Here, we present continuous measurements of local IOP values in the anterior chamber and vitreous chamber of living animals using minimally invasive probes with pressure-sensitive transistors. After inducing glaucoma in animal models, we compared the local IOP distribution between normal and glaucomatous eyes. We also compared IOP values detected in the cornea using tonometry measurements. Our findings revealed that glaucoma induced higher IOP in the vitreous chamber than in the anterior chamber, indicating that measuring IOP in the vitreous chamber is key to the glaucoma model. This progress offers future directions for diagnosis and treatment of glaucoma.

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

The eye contains a complex network of physiological information and biomarkers for monitoring disease and managing health, and ocular devices can be used to effectively perform point-of-care diagnosis and disease management. This comprehensive review describes the target biomarkers and various diseases, including ophthalmic diseases, metabolic diseases, and neurological diseases, based on the physiological and anatomical background of the eye. This review also includes the recent technologies utilized in eye-wearable medical devices and the latest trends in wearable ophthalmic devices, specifically smart contact lenses for the purpose of disease management. After introducing other ocular devices such as the retinal prosthesis, we further discuss the current challenges and potential possibilities of smart contact lenses.

Wireless Non-Invasive Monitoring of Cholesterol Using a Smart Contact Lens.

Herein, a wireless and soft smart contact lens that enables real-time quantitative recording of cholesterol in tear fluids for the monitoring of patients with hyperlipidemia using a smartphone is reported. This contact lens incorporates an electrochemical biosensor for the continuous detection of cholesterol concentrations, stretchable antenna, and integrated circuits for wireless communication, which makes a smartphone the only device required to operate this lens remotely without obstructing the wearer's vision. The hyperlipidemia rabbit model is utilized to confirm the correlation between cholesterol levels in tear fluid and blood and to confirm the feasibility of this smart contact lens for diagnostic application of cholesterol-related diseases. Further in vivo tests with human subjects demonstrated its good biocompatibility, wearability, and reliability as a non-invasive healthcare device.

High-Resolution 3D Printing for Electronics.

The ability to form arbitrary 3D structures provides the next level of complexity and a greater degree of freedom in the design of electronic devices. Since recent progress in electronics has expanded their applicability in various fields in which structural conformability and dynamic configuration are required, high-resolution 3D printing technologies can offer significant potential for freeform electronics. Here, the recent progress in novel 3D printing methods for freeform electronics is reviewed, with providing a comprehensive study on 3D-printable functional materials and processes for various device components. The latest advances in 3D-printed electronics are also reviewed to explain representative device components, including interconnects, batteries, antennas, and sensors. Furthermore, the key challenges and prospects for next-generation printed electronics are considered, and the future directions are explored based on research that has emerged recently.

Synthesis of electrically conductive and superparamagnetic monodispersed iron oxide-conjugated polymer composite nanoparticles by in situ chemical oxidative polymerization.

Core-shell nanocomposites composed of iron oxide (Fe3O4) nanoparticles and conjugated polymer, poly(3, 4-ethylenedioxythiophene) (PEDOT), were successfully synthesized from a simple and inexpensive in situ chemical oxidative polymerization of EDOT with Fe3O4 nanoparticles in the micellar solution of lignosulfonic acid (LSA) which serves as both a surfactant and a dopant. These nanocomposites (Fe3O4-PEDOT) were subsequently characterized for morphological, crystalline, structural, electrical and magnetic properties by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), four-probe meter and superconductor quantum interference device (SQUID), respectively. Results show that the nanocomposites have a spherical core-shell shape, are approximately 10 nm in size and are superparamagnetic with good magnetic saturation and good electrical conductivities. Existence of Fe3O4 in the nanocomposites was confirmed by using Energy dispersive X-ray photoelectron spectroscopy (EDAX) and X-ray photoelectron microscopy (XPS). We also investigated a possible formation mechanism of the core-shell nanocomposites, and the effect of Fe3O4 nanoparticles on the electro-magnetic properties of the nanocomposites. Such novel conducting and superparamagnetic composite nanomaterials can be applied to sensors, magnetic data storage, electro-magnetic resonance wave absorption, etc.