Dae-Hyeong Kim’s research while affiliated with Institute for Basic Science and other places

Soft implantable multichannel cardiac electrode arrays that establish direct monolithic interfaces with the heart are key components for advanced cardiac monitoring and electrical modulation. A significant technological advancement in this area is the development of stretchable conductive nanocomposites, fabricated through the integration of metallic nanomaterials and elastic polymers, aimed at achieving both high electrical conductivity and mechanical elasticity. Despite these advances, further progress in material performance and device designs is required to ensure seamless, reliable, biocompatible, and high‐fidelity cardiac interfacing. Herein, the development of a soft multichannel cardiac patch based on a bifacial architecture of adhesive/low‐impedance hydrogel nanocomposites and highly conductive elastomer nanocomposites is reported. The bifacial design facilitates the integration of the cardiac patch between the heart and other tissues/organs can be achieved. The hydrogel nanocomposite layer, positioned on the epicardial side, provides stable adhesion to the target cardiac tissue and enables low‐impedance biocompatible interfacing with the heart, while the elastomer nanocomposite layer, positioned on the opposite side, offers high electrical conductivity for facile electrophysiological signal transfer and a low‐friction surface minimizing unwanted interactions with surrounding tissues. The effectiveness of this bifacial patch in multiple applications involving various cardiac signal recordings and electromechanical modulation demonstrations is showcased.

Continuous monitoring systems that effectively manage neurological disorders and cardiovascular diseases are crucial for enhancing the quality of life in aging societies. Soft implantable bioelectronics, which consists of soft devices with mechanical properties akin to biological tissues, are promising candidates for such monitoring systems. These devices enable conformal integration with target tissues, minimizing adverse side effects during their long-term use. They also precisely monitor physiological conditions, facilitating tailored therapeutic interventions based on individual physiological responses. This review highlights recent advancements in soft implantable bioelectronics for managing neurological disorders and cardiovascular diseases. Specifically, strategies for the materials, device fabrication, and their integration with the biological tissues are reviewed in detail first. Then, the challenges in translating these technologies into practical applications are addressed, including the integration of artificial intelligence (AI) technologies.

In robotics, particularly for autonomous navigation and human–robot collaboration, the significance of unconventional imaging techniques and efficient data processing capabilities is paramount. The unstructured environments encountered by robots, coupled with complex missions assigned to them, present numerous challenges necessitating diverse visual functionalities, and consequently, the development of multifunctional robotic vision systems has become indispensable. Meanwhile, rich diversity inherent in animal vision systems, honed over evolutionary epochs to meet their survival demands across varied habitats, serves as a profound source of inspirations. Here, recent advancements in multifunctional robotic vision systems drawing inspiration from natural ocular structures and their visual perception mechanisms are delineated. First, unique imaging functionalities of natural eyes across terrestrial, aerial, and aquatic habitats and visual signal processing mechanism of humans are explored. Then, designs and functionalities of bio‐inspired electronic eyes are explored, engineered to mimic key components and underlying optical principles of natural eyes. Furthermore, neuromorphic image sensors are discussed, emulating functional properties of synapses, neurons, and retinas and thereby enhancing accuracy and efficiency of robotic vision tasks. Next, integration examples of electronic eyes with mobile robotic/biological systems are introduced. Finally, a forward‐looking outlook on the development of bio‐inspired electronic eyes and neuromorphic image sensors is provided.

Biologically inspired artificial vision research has led to innovative robotic vision systems with low optical aberration, wide field of view, and compact form factor. However, challenges persist in object detection and recognition against complex backgrounds and varied lighting. Inspired by the feline eye, which features a vertically elongated pupil and tapetum lucidum, this study introduces an artificial vision system designed for superior object detection and recognition in a monocular framework. Using a slit-like elliptical aperture and a patterned metal reflector beneath a hemispherical silicon photodiode array, the system reduces excessive light and enhances photosensitivity. This design achieves clear focus under bright light and enhanced sensitivity in dim conditions. Theoretical and experimental analyses demonstrate the system’s ability to filter redundant information and detect camouflaged objects in diverse lighting, representing a substantial advancement in monocular camera technology and the potential of biomimicry in optical innovations.

Recent advancements in artificial intelligence (AI) technologies, particularly machine learning (ML) techniques, have opened up a promising frontier in the development of intelligent soft bioelectronics, demonstrating unparalleled performance in interfacing with the human body. Hydrogels, owing to their unique combination of biocompatibility, tunable mechanical properties, and high water content, have emerged as a versatile platform for constructing soft bioelectronic devices. Functionalized hydrogels, such as conductive hydrogels, can efficiently capture biosignals from various target tissues while seamlessly forming conformal and reliable interfaces. They can also function as an intermediary layer between biological tissues and soft bioelectronics for diagnosis and therapy purposes. Meanwhile, ML has demonstrated its efficacy in processing extensive datasets collected from the bioelectronics. The convergence of hydrogel‐based soft bioelectronics and ML has unlocked a myriad of possibilities in unprecedented diagnostics, therapeutics, and beyond. In this review, the latest advances in hydrogel‐based soft bioelectronics are introduced. After briefly describing the materials and device strategies for high‐performance hydrogel bioelectronics, how ML can be integrated to augment the functionalities is discussed. Recent examples of ML‐integrated hydrogel bioelectronics are then discussed. Finally, the review is concluded by introducing future potential applications of AI in hydrogel‐based bioelectronics, alongside inherent challenges in this interdisciplinary domain.

The low electrical conductivity of conductive hydrogels limits their applications as soft conductors in bioelectronics. This low conductivity originates from the high water content of hydrogels, which impedes facile carrier transport between conductive fillers. This study presents a highly conductive and stretchable hydrogel nanocomposite comprising whiskered gold nanosheets. A dry network of whiskered gold nanosheets is fabricated and then incorporated into the wet hydrogel matrices. The whiskered gold nanosheets preserve their tight interconnection in hydrogels despite the high water content, providing a high‐quality percolation network even under stretched states. Regardless of the type of hydrogel matrix, the gold‐hydrogel nanocomposites exhibit a conductivity of ≈520 S cm⁻¹ and a stretchability of ≈300% without requiring a dehydration process. The conductivity reaches a maximum of ≈3304 S cm⁻¹ when the density of the dry gold network is controlled. A gold‐adhesive hydrogel nanocomposite, which can achieve conformal adhesion to moving organ surfaces, is fabricated for bioelectronics demonstrations. The adhesive hydrogel electrode outperforms elastomer‐based electrodes in in vivo epicardial electrogram recording, epicardial pacing, and sciatic nerve stimulation.

Deformable light-emitting devices, capable of maintaining consistent light emission even under mechanical deformations, represent a cornerstone for next-generation human-centric electronics. Quantum dot light-emitting diodes (QLEDs), leveraging the electroluminescence (EL) of colloidal quantum dots (QDs), show exceptional promise in this domain. Their superior advantages, such as excellent color purity, high luminous efficiency, slim form factor, and facile fabrication on various soft substrates, position them as prime candidates for deformable EL devices. This review explores recent advancements in deformable QLEDs, with a particular focus on material engineering and fabrication strategies. We begin by introducing various types of QDs and the operational principles of QLEDs, along with summarizing performance enhancements in reported deformable devices. Next, we categorize device structures based on the direction of light emission. We then discuss representative methods for patterning QD thin films on flexible substrates to fabricate full-color QLEDs. Additionally, we highlight fabrication strategies for deformable QLEDs with unconventional form factors, including flexible, foldable, fiber-type, and stretchable devices, and their potential applications. We conclude this review with a brief outlook on the future of this technology.