Frequency-encoded eye tracking smart contact lens for human-machine interaction.

Eye tracking techniques enable high-efficient, natural, and effortless human-machine interaction by detecting users' eye movements and decoding their attention and intentions. Here, a miniature, imperceptible, and biocompatible smart contact lens is proposed for in situ eye tracking and wireless eye-machine interaction. Employing the frequency encoding strategy, the chip-free and battery-free lens successes in detecting eye movement and closure. Using a time-sequential eye tracking algorithm, the lens has a great angular accuracy of <0.5°, which is even less than the vision range of central fovea. Multiple eye-machine interaction applications, such as eye-drawing, Gluttonous Snake game, web interaction, pan-tilt-zoom camera control, and robot vehicle control, are demonstrated on the eye movement model and in vivo rabbit. Furthermore, comprehensive biocompatibility tests are implemented, demonstrating low cytotoxicity and low eye irritation. Thus, the contact lens is expected to enrich approaches of eye tracking techniques and promote the development of human-machine interaction technology.

Hydrogel-Based Smart Contact Lens for Highly Sensitive Wireless Intraocular Pressure Monitoring.

Real-time intraocular pressure (IOP) monitoring plays a crucial role in glaucoma diagnosis and treatment. The wireless smart contact lens based on a flexible inductor-capacitor-resistor (LCR) sensor is chip-free and battery-free, demonstrating excellent application potential for physiological signal monitoring. To promote the use of LCR contact lenses for clinical IOP monitoring, reliable, comfortable contact lens materials should be used and excellent sensitivity needs to be realized. Here, we propose a method for producing hydrogel-based smart contact lenses for wireless IOP monitoring that uses the conformal stacking technique, solving the problems of swelling of the hydrogel and spherical integration of the pyramid-microstructured dielectric elastomer. The IOP of the in vitro porcine eye is successfully monitored owing to the high sensitivity of the spherical pyramid-microstructured capacitive pressure sensor and the hydrogel substrate. In addition, a glasses-integrated impedance-matching tunable reader for remote signal measurement is realized by enhancing the signal amplitude and increasing the reading distance, improving the portability of the signal measurement equipment. With the above improved designs, the wireless contact lens system has application potential for clinical IOP monitoring and shows substantial promise for next-generation daily ocular health management.

Optical fiber tip integrated photoelectrochemical sensors.

In this work, we design and fabricate a compact photoelectrochemical (PEC) sensor by integrating a graphene-MoS2 heterostructure on an optical fiber tip. The graphene serves as a transparent carrier transport layer, and the MoS2 presents a photoelectrical transducer that generates photocarriers and interacts with ascorbic acid (AA) in solution. This device is used to demonstrate a self-powered detection of AA with a concentration range between 1 mM and 50 mM, and a time response of ∼ 6 ms. The device downsizes traditional PEC systems to the micrometer scale, benefiting the real-time monitoring of biochemical changes in small areas and opening the pathway for miniaturized PEC sensing applications.

Ultrahigh Responsivity Photodetectors of 2D Covalent Organic Frameworks Integrated on Graphene.

2D materials exhibit superior properties in electronic and optoelectronic fields. The wide demand for high-performance optoelectronic devices promotes the exploration of diversified 2D materials. Recently, 2D covalent organic frameworks (COFs) have emerged as next-generation layered materials with predesigned π-electronic skeletons and highly ordered topological structures, which are promising for tailoring their optoelectronic properties. However, COFs are usually produced as solid powders due to anisotropic growth, making them unreliable to integrate into devices. Here, by selecting tetraphenylethylene monomers with photoelectric activity, elaborately designed photosensitive 2D-COFs with highly ordered donor-acceptor topologies are in situ synthesized on graphene, ultimately forming COF-graphene heterostructures. Ultrasensitive photodetectors are successfully fabricated with the COFETBC-TAPT -graphene heterostructure and exhibited an excellent overall performance with a photoresponsivity of ≈3.2 × 107 A W-1 at 473 nm and a time response of ≈1.14 ms. Moreover, due to the high surface area and the polarity selectivity of COFs, the photosensing properties of the photodetectors can be reversibly regulated by specific target molecules. The research provides new strategies for building advanced functional devices with programmable material structures and diversified regulation methods, paving the way for a generation of high-performance applications in optoelectronics and many other fields.

A Flexible Wireless Dielectric Sensor for Noninvasive Fluid Monitoring.

A flexible wireless dielectric sensor is presented here for noninvasively monitoring the permittivity and conductivity of fluids, based on resistor-inductor-capacitor (RLC) resonant circuit and capacitively coupled contactless conductivity detection (C4D) technique. The RLC sensor consists of one single-turn inductor and one interdigital capacitor. The resonant frequency of the device is sensitive to the surrounding environment, thanks to the electric field leaked out between the interdigital capacitor electrodes. Through the high-frequency structure simulator (HFSS) simulation, and experiments on ethanol/water solutions and NaCl solutions, it was confirmed that a fluid's permittivity and conductivity could be detected by the return loss curve (S11). With great repeatability and stability, the proposed sensor has potential for broad applications, especially in wearable low-cost smart devices.