Search Results (78)

This review examines recent advances in multifunctional probes that integrate optical and electrochemical channels for in vitro/in vivo studies. Integration of electrodes with optical fibers provides a powerful platform for localized light delivery and simultaneous electrochemical detection of cellular metabolites both within and at the surface of single living cells. These hybrid devices bridge optical stimulation methods, including optogenetics, and electrochemical monitoring of the cellular response within the same experimental preparation. The review systematically categorizes distinct probe architectures: optical nanoendoscopes for intracellular measurements, probes with a shared opto-electrochemical channel, devices where optical and electrochemical channels are physically separated, and probes engineered for neural interfaces and scanning probe microscopy. For each category, fabrication approaches, surface modification strategies, and representative biological applications are discussed. Particular attention is given to the fundamental tension between optical transparency and electrical conductivity in shared-channel designs, to the mechanical requirements imposed by neural tissue on implantable probes, and to the spatial resolution limits of current scanning probe platforms. The review concludes with a critical assessment of current limitations and future directions, including higher spatial resolution, simultaneous multiplexed analyte detection and broader translation of these technologies toward in vivo experimental models. Full article

Brain-on-a-chip (BOC) refers to a miniaturized in vitro platform that integrates living neuronal networks on a micro-engineered chip, enabling the simulation of brain functions, neural activities and physiological responses. BOC technology is an advanced evolution of microphysiological systems (MPS) and Lab-on-a-Chip platforms, providing novel paradigms for in vitro modeling and exploring early-stage biocomputing by interfacing living neural networks with engineered electronics. Microelectrode arrays (MEAs) serve as the critical physical interface for bidirectional communication in these systems. In this review, we systematically examine the technological landscape and engineering requirements of MEAs tailored for BOC applications, evaluating them across electrical characteristics, structural properties, and biocompatibility. Two primary classes of current MEA technologies, including planar arrays for 2D neural cultures and 3D flexible arrays for brain organoids, are discussed in detail. We highlight the transition from passive planar electrodes to high-density active CMOS and TFT-based arrays, and detail how 3D flexible MEAs utilize endogenous integration and exogenous wrapping strategies to overcome tissue-mechanics mismatches. Furthermore, the integration of MEAs with microfluidics, optoelectronics, and electrochemical sensors to enable multimodal monitoring is explored. With the advantages of the various MEAs, the application of MEAs for BOC, particularly in biological computing and network plasticity research, is discussed. Finally, future technological developments in scalability bottlenecks, chronic stability, and the incorporation of artificial intelligence for MEAs of BOC are prospected. Full article

Objectives: We aimed to investigate the short-term effects of preoperative postauricular glucocorticoid (GC) injection on electrode impedance in cochlear implant (CI) recipients. Methods: A total of 69 participants were enrolled: 44 children (<18 years) and 25 adults (18–85 years). Using a pre-specified non-randomized alternating assignment strategy, they were respectively assigned to either the treatment group (preoperative postauricular methylprednisolone injection and intraoperative intratympanic betamethasone) or the control group (intraoperative intratympanic betamethasone alone). Electrode impedance was measured intraoperatively and at 1, 3, and 6 months postoperatively. Owing to the use of different implant systems in pediatric and adult patients, the two cohorts were analyzed separately. Longitudinal impedance data across cochlear turns (apex, middle, base) were analyzed using linear mixed-effects models adjusted for baseline values. This study was registered on Chictr.org.cn (ChiCTR2400081024). Results: In the pediatric cohort, a significant interaction between group and time was observed (F = 8.34, p < 0.001); however, post hoc analyses did not demonstrate statistically significant differences between groups at individual postoperative time points (all p > 0.05). In the adult cohort, a significant interaction between group and turn was identified (F = 3.07, p = 0.049); post hoc analysis demonstrated statistically significant differences in impedance in the middle turn between groups (intervention effect = 1.355 kΩ; 95% CI, 0.115 to 2.596; p = 0.033). Conclusions: Preoperative postauricular GC administration, when combined with intraoperative intratympanic steroid therapy, may be associated with differences in postoperative electrode impedance dynamics and the electrode–tissue interface. Full article

Physics-based simulations are increasingly used to improve understanding of electrosurgical processes and to enable model-based estimation of tissue state when direct sensing is limited. The performance of such simulation-based virtual sensing approaches strongly depends on an accurate representation of the electrode–tissue interface. Despite its central role in electrical and thermal coupling, the influence of the electrode–tissue contact area has received limited attention in existing simulation studies. In this work, the influence of the electrode–tissue contact area on the sensitivity of key temperature-dependent tissue parameters was investigated for electrosurgical monopolar soft coagulation. Using a multiphysics finite element model under controlled boundary conditions, the sensitivity of maximum temperature development and necrotic tissue volume formation was analyzed with respect to varying contact areas and initial values of electrical conductivity, thermal conductivity, and effective heat capacity. The results demonstrate that parameter sensitivities are strongly contact-area-dependent. Electrical conductivity exhibits the most pronounced influence, particularly at larger contact areas, while thermal conductivity remains of minor relevance. In contrast, effective heat capacity significantly affects necrotic tissue volume formation, with increasing sensitivity for larger contact areas. These findings emphasize the importance of accurately accounting for electrode–tissue contact conditions in simulation-based analyses and clarify how contact-area-dependent sensitivities influence model-based tissue state estimation in electrosurgical coagulation. Full article

High-resolution, multi-modal neural interfaces are essential for advancing systems neuroscience and brain–computer interface technologies. This study designed and fabricated a 128-channel comb-shaped flexible micro-electrode array. The device integrates a biocompatible Parylene substrate with a flexible thin-film microprobe array, enabling simultaneous recording of electrocorticography (ECoG), intracortical local field potentials (LFP), and neuronal action potentials (spikes) from the cortical surface and superficial layers. Microelectrode sites were modified with platinum black nanoparticles, significantly reducing impedance. In vivo experiments in rats demonstrated the array’s ability to capture high-fidelity signals across different recording depths. Key findings included the acquisition of opposing LFP trends and polarity reversals between adjacent channels, reflecting local microcircuit dynamics. The array also reliably recorded neural activity during audiovisual cross-modal sensory stimulation. These results validate the device as an effective tool for multi-scale electrophysiology, successfully balancing high spatial resolution and signal quality with minimal tissue invasiveness, thereby offering significant potential for fundamental research and neural engineering applications. Full article

Flexible sensors have emerged as critical interfaces for information exchange between soft biological tissues and machines. Here, we present a dual-mode stretchable sensor system capable of synchronous strain and electromyography (EMG) signal detection, integrated with wireless WIFI transmission for real-time joint movement monitoring. The system consists of two key components: (1) A multi-channel gel electrode array for high-fidelity EMG signal acquisition from target muscle groups, and (2) a novel capacitive strain sensor made of stretchable micro-cracked gold film based on Styrene Ethylene Butylene Styrene (SEBS) that exhibits exceptional performance, including >80% stretchability, >4000-cycle durability, and fast response time (<100 ms). The strain sensor demonstrates position-independent measurement accuracy, enabling robust joint angle detection regardless of placement variations. Through synchronized mechanical deformation and electrophysiological monitoring, this platform provides comprehensive movement quantification, with data visualization interfaces compatible with mobile and desktop applications. The proposed technology establishes a generalizable framework for multimodal biosensing in human motion analysis, robotics, and human–machine interaction systems. Full article

The development of implantable neural interfaces is essential for enabling bidirectional communication between the nervous system and prosthetic devices, yet their evaluation still relies primarily on in vivo models which are costly, variable, and ethically constrained. Here, we report a bio-inspired artificial nerve simulator engineered as a reproducible ex vivo platform for pre-implantation testing of plug-type electrodes. The simulator is fabricated from a conductive hydrogel composite based on reduced graphene oxide (rGO), polyaniline (PANI), agarose, sucrose, and sodium chloride, with embedded conductive channels that replicate the fascicular organization and conductivity of peripheral nerves. The resulting construct exhibits impedance values of ~2.4–2.9 kΩ between electrode needles at 1 kHz, closely matching in vivo measurements (~2 kΩ) obtained in Sus scrofa domesticus nerve tissue. Its structural and electrical fidelity enables systematic evaluation of electrode–nerve contact properties, signal transmission, and insertion behavior under controlled conditions, while reducing reliance on animal experiments. This bio-inspired simulator offers a scalable and physiologically relevant testbed that bridges materials engineering and translational neuroprosthetics, accelerating the development of next-generation implantable neural interfaces. Full article

Cochlear implants are highly successful in restoring speech perception but variability in outcomes exists. Post-surgical fibrosis and neo-ossification are thought to play a significant role, being linked to increased impedance and loss of residual hearing and posing challenges for re-implantation. Hence, there is growing interest in pharmacological interventions to limit intracochlear fibrosis and neo-ossification. While current approaches focus on steroids, studies in other organs have identified many candidate drugs. However, selection is hindered by a limited understanding of the molecular and cellular mechanisms driving fibrosis after implantation. This review introduces potential drug candidates for cochlear implant-induced fibrosis, with many targeting core fibrotic pathways such as TGF-β/SMAD, PDGF, and Wnt/β-catenin or inhibiting pro-inflammatory signalling. By drawing on lessons from other tissues, this review identifies mechanisms and therapeutic approaches adaptable to the cochlea. Understanding fibrosis across organs will guide strategies to prevent or reverse cochlear fibrosis. Their translation requires careful evaluation of local delivery, minimal ototoxicity, and effects on the electrode–tissue interface. Full article

The convergence of flexible electronics and miniaturized ultrasound transducers has accelerated the development of wearable ultrasound devices, offering innovative solutions for continuous, non-invasive physiological monitoring and disease diagnosis. This review systematically examines the recent progress in the field, focusing on three key aspects: physical principles, device design, and clinical applications. From the perspective of physical principles, we provide an in-depth analysis of the fundamental theories underlying ultrasound imaging, including acoustic wave propagation in biological tissues, interface reflection mechanisms, and Doppler effects. In terms of device design, we compare technical approaches for rigid and flexible ultrasound transducers, with particular emphasis on innovative designs for flexible transducers. The key developments discussed include optimization of piezoelectric materials, the fabrication of stretchable electrodes, and advances in flexible encapsulation materials. Regarding clinical applications, we categorize the use cases by anatomical region and illustrate their diagnostic value through representative examples, demonstrating their utility in disease detection, health monitoring, and sports medicine. Finally, we identify critical challenges such as signal stability, coupling material compatibility, and long-term wearability, while outlining future directions including AI-assisted diagnosis and multifunctional integration. This review aims to provide a comprehensive reference for both fundamental research and clinical translation of wearable ultrasound technologies. Full article

Brain ischemia is a severe condition caused by reduced cerebral blood flow, leading to the disruption of ion gradients in brain tissue. This imbalance triggers spreading depolarizations, which are waves of neuronal and glial depolarization propagating through the gray matter. Microelectrode arrays (MEAs) are essential for real-time monitoring of these electrophysiological processes both in vivo and in vitro, but their sensitivity and signal quality are critical for accurate detection of extracellular brain activity. In this study, we evaluate the performance of a flexible microelectrode array based on gold-coated zinc oxide nanorods (ZnO NRs), referred to as nano-fMEA, specifically for high-fidelity electrophysiological recording under pathological conditions. Acute mouse brain slices were tested under two ischemic models: oxygen–glucose deprivation (OGD) and hyperkalemia. The nano-fMEA demonstrated significant improvements in event detection rates and in capturing subtle fluctuations in neural signals compared to flat fMEAs. This enhanced performance is primarily attributed to an optimized electrode–tissue interface that reduces impedance and improves charge transfer. These features enabled the nano-fMEA to detect weak or transient electrophysiological events more effectively, making it a valuable platform for investigating neural dynamics during metabolic stress. Overall, the results underscore the promise of ZnO NRs in advancing electrophysiological tools for neuroscience research. Full article

Background: The increasing use of technologies operating between 10 and 200 kHz, such as RFID, wireless power transfer systems, and induction cooktops, raises concerns about electromagnetic interference (EMI) with cardiac implantable electronic devices (CIEDs). The mechanisms of interaction within this frequency range have been only partially addressed by both the scientific and regulatory communities. Methods: A physical twin of a pacemaker/implantable defibrillator (PM/ICD) was developed to experimentally assess voltages induced at the input stage by low-to-mid-frequency magnetic fields. The setup simulates the two sensing modalities programmable in PMs/ICDs and allows for the analysis of different implant configurations, lead geometries, and positions within a human body phantom. Results: Characterization of the physical twin demonstrated its capability to reliably measure induced voltages in the range of 5 mV to 1.5 V. Its application enabled the identification of factors beyond the implant’s induction area that contribute to the induced voltage, such as the electrode-tissue interface and body-induced currents. Conclusions: This physical twin represents a valuable tool for experimentally validating the mechanisms of EMI in CIEDs, providing insights beyond current standards. The data obtained can serve as a reference for the validation of numerical models and patient-specific digital twins. Moreover, it offers valuable information to guide future updates and revisions of international electromagnetic compatibility standards for CIEDs. Full article

This work presents an innovative bioimpedance spectroscopy device, developed as a support tool for decision-making during the evaluation of kidney viability for renal transplantation. Given the increasing demand for organs and the need to optimize donation criteria, the precise and objective assessment of renal graft functionality has become crucial. The device, based on a modular design and adapted to the surgical environment, uses a novel Cole model with a frequency-dependent membrane capacitance, which improves measurement accuracy and repeatability compared to conventional models. Adapting the device for operating room usege involved overcoming significant challenges, such as the need for sterilization and a visual, tactile and acoustic user interface that facilitates device usability. Optimizing the sensing stage has minimized the influence of measurement artifacts, which is crucial for obtaining accurate and representative measurements of renal tissue bioelectrical properties. In addition, a rigorous electrode sterilization protocol was designed, ensuring asepsis during the procedure. The results of tests on porcine renal models demonstrated the device’s ability to monitor pathophysiological changes associated with renal ischemia, with a notable improvement against measurement repeatability. Full article

Background: Scientists have recently developed a technology that induces artificial taste through electronic stimulation. However, scattered reports have made it difficult to comprehensively understand the technology’s details and appreciate its potential applications in healthcare. To address these gaps, a meta-review was conducted. We re-viewed the current literatures on the technology behind artificial taste. Targeted original research papers were analyzed, with data extracted to address five key aspects: interface design, stimulation parameters, sensation verification results, applications to health problems, and potential side effects in human subjects. Results: A total of 19 relevant papers were identified. Eight studies focused on tongue-tip electrode interfaces, while others integrated technology into eating utensils. Eleven studies examined stimulation frequencies (50–1000 Hz), with five altering temperature and two changing water color to enhance taste perception. Only six studies reported verification results, showing that most participants perceived sour and salty tastes, mild bitter responses, and unreliable sweet evocation. Sixteen papers discussed applications in healthcare (dietary and weight management), entertainment (food and beverage sampling), and education. Side effects included reduced sensitivity after repeated trials and occasional discomfort from excessive stimulation, though no immediate tissue damage was reported. Conclusions: Artificial taste technology offers an innovative approach to managing food and beverage intake without compromising taste sensations. When applied on a large scale, it holds significant potential for regulating eating behaviors and providing novel strategies for addressing chronic health issues associated with diet. Full article

Minimally invasive endovascular stent electrodes are an emerging technology in neural engineering, designed to minimize the damage to neural tissue. However, conventional stent electrodes often rely on resistive welding and are relatively bulky, restricting their use primarily to large animals or thick blood vessels. In this study, the feasibility is explored of fabricating a laser welding stent electrode as small as 300 μm. A high-precision laser welding technique was developed to join micro-wire electrodes without compromising structural integrity or performance. To ensure consistent results, a novel micro-wire welding with platinum pad method was introduced during the welding process. The fabricated electrodes were integrated with stent structures and subjected to detailed electrochemical performance testing to evaluate their potential as neural interface components. The laser-welded endovascular stent electrodes exhibited excellent electrochemical properties, including low impedance and stable charge transfer capabilities. At the same time, in this study, a simulation is conducted of the electrode distribution and arrangement on the stent structure, optimizing the utilization of the available surface area for enhanced functionality. These results demonstrate the potential of the fabricated electrodes for high-performance neural interfacing in endovascular applications. The approach provided a promising solution for advancing endovascular neural engineering technologies, particularly in applications requiring compact electrode designs. Full article

The aim of this work is to incorporate lanthanide-cored upconversion nanoparticles (UCNP) into the surface of microengineered biomedical implants to create a spatially controlled and optically releasable model drug delivery device in an integrated fashion. Our approach enables silicone-based microelectrocorticography (ECoG) implants holding platinum/iridium recording sites to serve as a stable host of UCNPs. Nanoparticles excitable in the near-infrared (lower energy) regime and emitting visible (higher energy) light are utilized in a study. With the upconverted higher energy photons, we demonstrate the induction of photochemical (cleaving) reactions that enable the local release of specific dyes as a model system near the implant. The modified ECoG electrodes can be implanted in brain tissue to act as an uncaging system that releases small amounts of substance while simultaneously measuring the evoked neural response upon light activation. In this paper, several technological challenges like the surface modification of UCNPs, the immobilization of particles on the implantable platform, and measuring the stability of integrated UCNPs in in vitro and in vivo conditions are addressed in detail. Besides the chemical, mechanical, and optical characterization of the ready-to-use devices, the effect of nanoparticles on the original electrophysiological function is also evaluated. The results confirm that silicone-based brain–machine interfaces can be efficiently complemented with UCNPs to facilitate local model drug release. Full article