Yeji Kim

Neuromodulators such as dopamine (DA) operate through volume transmission in the brain, creating spatially distributed fields that shape circuit excitability. However, conventional sensing modalities, including voltammetry and fiber photometry, inherently collapse these multidimensional dynamics into one-dimensional, single-point signals, thereby obscuring spatial heterogeneity and propagation behavior. Here, we introduce the Neural Remote Imaging Fiber Interface (NeuRIFI), a dual-readout near-infrared (NIR) sensing platform that bridges localized neurochemical detection and field-level spatial interpretation. By functionalizing implantable optical fibers with DNA-functionalized SWCNT nanosensors, this platform leverages NIR fluorescence emission within the tissue-transparent optical window to enable synchronous fiber-guided photometry and remote NIR imaging without genetic labeling. In this configuration, the photometric channel provides a spatially anchored validation reference, while the remote imaging channel preserves the spatial information on neurochemical signals. We validated the interface across tissue phantoms and ex vivo mouse brains, demonstrating reliable deep-brain signal acquisition at a 3 mm depth. Furthermore, by computing frame-to-frame intensity derivatives, we resolved transient DA flux at a temporal resolution of 20 ms, a spatial resolution of ∼1.5 μm per pixel, and a concentration sensitivity of 90 nM, enabling high spatiotemporal resolution mapping of neurochemical transport across the sensing surface. Collectively, this dual-readout architecture provides a framework linking point-validated sensing to remotely observable spatial structures, offering spatial accessibility for studying complex neurochemical landscapes in deep-brain structures and extending neurochemical field mapping toward in vivo settings.

Neurochemical signalling has emerged as a rapid, versatile and indispensable layer of neural computation, operating alongside electrical activity to shape circuit dynamics, behaviour and disease progression. Decoding these signals in vivo requires sensing platforms that combine spatiotemporal resolution, molecular specificity and anatomical compatibility, capabilities beyond those of traditional sampling methods. Electrochemical technologies, from fast-scan cyclic voltammetry to molecular recognition sensors, deliver subsecond temporal resolution without genetic manipulation, whereas optical approaches using genetically encoded indicators achieve cell-specific measurements with high spatial precision. However, most existing implementations provide only a single sensing function, restricting measurements to a passive chemical dimension and limiting comprehensive or causal circuit analysis. Hybrid systems begin to bridge this gap by coupling stimulation and sensing within unified interfaces, enabling richer interrogation of brain networks. Building on this foundation, transformative multimodal platforms fundamentally expand the boundaries of chemical sensing, overcoming limitations in scope, resolution and accessibility, to enable brain-wide, multianalyte and remote operation. In doing so, they elevate in vivo neurochemical sensing to a frontier discipline, offering unprecedented opportunities to map, decode and therapeutically modulate the chemical logic that underlies cognition, behaviour and pathology.

Recent advancements in implantable bioelectronic devices have increased the demand for biocompatible energy sources with long-term electrochemical and mechanical stability. Here, we present a tough hydrogel-based supercapacitor (THBS) fiber, fabricated via a thermal drawing process (TDP), that enables the integration of all components—electrodes, electrolyte, current collectors, and encapsulation—into a single, unified, and mechanically robust fiber-shaped architecture. Through thermal/mechanical optimization and the incorporation of self-healing properties, THBS fibers exhibit durable, high electrochemical performance under dynamic, high-curvature deformations mimicking in vivo physiological motions. Despite a thickness of only a few hundred microns, they maintain mechanical and electrochemical stability. Long-term functionality was confirmed over five weeks with minimal immune response. In vivo implantation demonstrated successful LED operation in a freely moving mouse, and successful optogenetic stimulation of both central and peripheral nervous systems. These results underscore the promise of THBS fibers as next-generation, fully biocompatible energy storage devices for advanced implantable bioelectronic systems.

Rapid diagnosis of cerebrospinal fluid (CSF) leaks is critical as endoscopic endonasal skull base surgery gains global prominence. Current clinical methods such as endoscopic examination with and without intrathecal injection of fluorescent dye are invasive and rely on subjective judgment by physicians, highlighting the clinical need for label-free point-of-care (POC). However, a viable solution remains undeveloped due to the molecular complexity of CSF rhinorrhea mixed with nasal discharge and the scarcity of specific biomarkers, delaying sensor development. In this study, we accelerated the development of a label-free CSF detection method for clinical use using a nanoparticle corona. We engineered corona nanointerfaces on near-infrared (nIR) fluorescent single-walled carbon nanotubes (SWCNTs) through noncovalent functionalization with 12 custom-designed poly(ethylene glycol) (PEG) lipids. By high-throughput screening of the corona library for the CSF biomarker β-trace protein (βTP), we selected the optimal corona, achieving a limit of detection (LOD) down to 1.46 mg/L, maintaining its selectivity even in human nasal discharge. Using molecular dynamics and docking simulations, we characterized the 3D morphology and βTP binding energy of the optimal corona in a quantified way. The corona nanosensor accurately diagnosed CSF leakages from eight patients having lumbar drainage and one patient with CSF leakage due to diverse diseases without any sample preparations. By integrating the nanosensor with custom-designed in vivo and in vitro form factors such as a camera and endoscope, we showed its potential for versatile and practical use in clinical settings. This accelerated sensor development platform can meet future urgent clinical demands for various diseases and conditions.

Pressure‐sensitive adhesives are widely utilized due to their instant and reversible adhesion to various dry substrates. Though offering intuitive and robust attachment of medical devices on skin, currently available clinical pressure‐sensitive adhesives do not attach to internal organs, mainly due to the presence of interfacial water on the tissue surface that acts as a barrier to adhesion. In this work, a pressure‐sensitive, repositionable bioadhesive (PSB) that adheres to internal organs by synergistically combining the characteristic viscoelastic properties of pressure‐sensitive adhesives and the interfacial behavior of hydrogel bioadhesives, is introduced. Composed of a viscoelastic copolymer, the PSB absorbs interfacial water to enable instant adhesion on wet internal organs, such as the heart and lungs, and removal after use without causing any tissue damage. The PSB's capabilities in diverse on‐demand surgical and analytical scenarios including tissue stabilization of soft organs and the integration of bioelectronic devices in rat and porcine models, are demonstrated.

Synapses in the brain utilize two distinct communication mechanisms: chemical and electrical. For a comprehensive investigation of neural circuitry, neural interfaces should be capable of both monitoring and stimulating these types of physiological interactions. However, previously developed interfaces for neurotransmitter monitoring have been limited in interaction modality due to constraints in device size, fabrication techniques, and the usage of flexible materials. To address this obstacle, we propose a multifunctional and flexible fiber probe fabricated through the microwire codrawing thermal drawing process, which enables the high-density integration of functional components with various materials such as polymers, metals, and carbon fibers. The fiber enables real-time monitoring of transient dopamine release in vivo, real-time stimulation of cell-specific neuronal populations via optogenetic stimulation, single-unit electrophysiology of individual neurons localized to the tip of the neural probe, and chemical stimulation via drug delivery. This fiber will improve the accessibility and functionality of bidirectional interrogation of neurochemical mechanisms in implantable neural probes.

High-fidelity and comfortable recording of electrophysiological (EP) signals with on-the-fly setup is essential for health care and human-machine interfaces (HMIs). Microneedle electrodes allow direct access to the epidermis and eliminate time-consuming skin preparation. However, existing microneedle electrodes lack elasticity and reliability required for robust skin interfacing, thereby making long-term, high-quality EP sensing challenging during body movement. Here, we introduce a stretchable microneedle adhesive patch (SNAP) providing excellent skin penetrability and a robust electromechanical skin interface for prolonged and reliable EP monitoring under varying skin conditions. Results demonstrate that the SNAP can substantially reduce skin contact impedance under skin contamination and enhance wearing comfort during motion, outperforming gel and flexible microneedle electrodes. Our wireless SNAP demonstration for exoskeleton robot control shows its potential for highly reliable HMIs, even under time-dynamic skin conditions. We envision that the SNAP will open new opportunities for wearable EP sensing and its real-world applications in HMIs.

Development of neural interfaces from surface electrodes to fibers with various type, functionality, and materials.