Investigation of Structural, Optical, Electrical, and Biological Properties of a Porous Platinum Electrode for Neurostimulation Devices

The structural and optical properties, as well as the electrical and biological characteristics of a porous platinum (Pt) structure for neurostimulation applications, are investigated. Critical factors such as biocompatibility, electrical performance, and structural and optical differences, which can adversely affect the functionality of implantable devices, are systematically analyzed and compared with general electrodes. By employing an integration of three-dimensional simulations and implantation experiments, we demonstrate that the remarkably extensive surface area, low reflectance, and outstanding peak current values inherent in porous Pt facilitate effective stimulation while simultaneously ensuring a high degree of biological safety. Our findings suggest that these beneficial characteristics collectively position porous Pt as a notably promising candidate for implantable electrodes in biomedical devices.

Electrode-Electrolyte Interface Modeling and Impedance Characterizing of Tripolar Concentric Ring Electrode

Electrodes are used to convert ionic currents to electrical currents in biological systems. Modeling the electrode-electrolyte interface and characterizing the impedance of the interface could help to optimize the performance of the electrode interface to achieve higher signal to noise ratios. Previous work has yielded accurate models for single-element biomedical electrodes. This paper introduces a model for a tripolar concentric ring electrode (TCRE) derived from impedance measurements using electrochemical impedance spectroscopy with a Ten20 electrode impedance matching paste. It is shown that the model serves well to predict the performance of the electrode-electrolyte interface for TCREs as well as standard cup electrodes. In this paper, we also discuss the comparison between the TCRE and the standard cup electrode regarding their impedance characterization and demonstrate the benefit of using TCREs in biomedical applications. We have also conducted auditory evoked potential experiments using both TCRE and standard cup electrodes. The results show that electroencephalography (EEG) recorded from tripolar concentric ring electrodes is beneficial, acquiring the auditory brainstem response with less stimuli with respect to recoding EEG using standard cup electrodes.

Development and Experimental Validation of a Dry Non-Invasive Multi-Channel Mouse Scalp EEG Sensor through Visual Evoked Potential Recordings

In this paper, we introduce a dry non-invasive multi-channel sensor for measuring brainwaves on the scalps of mice. The research on laboratory animals provide insights to various practical applications involving human beings and other animals such as working animals, pets, and livestock. An experimental framework targeting the laboratory animals has the potential to lead to successful translational research when it closely resembles the environment of real applications. To serve scalp electroencephalography (EEG) research environments for the laboratory mice, the dry non-invasive scalp EEG sensor with sixteen electrodes is proposed to measure brainwaves over the entire brain area without any surgical procedures. We validated the proposed sensor system with visual evoked potential (VEP) experiments elicited by flash stimulations. The VEP responses obtained from experiments are compared with the existing literature, and analyzed in temporal and spatial perspectives. We further interpret the experimental results using time-frequency distribution (TFD) and distance measurements. The developed sensor guarantees stable operations for in vivo experiments in a non-invasive manner without surgical procedures, therefore exhibiting a high potential to strengthen longitudinal experimental studies and reliable translational research exploiting non-invasive paradigms.

Soft implantable microelectrodes for future medicine: prosthetics, neural signal recording and neuromodulation

Implantable devices have provided various potential diagnostic options and therapeutic methods in diverse medical fields. A variety of hard-material-based implantable electrodes have been developed. However, several limitations for their chronic implantation remain, including mechanical mismatches at the interface between the electrode and the soft tissue, and biocompatibility. Soft-material-based implantable devices are suitable candidates for complementing the limitations of hard electrodes. Advances in microtechnology and materials science have largely solved many challenges, such as optimization of shape, minimization of infection, enhancement of biocompatibility and integration with components for diverse functions. Significant strides have also been made in mechanical matching of electrodes to soft tissue. In this review, we provide an overview of recent advances in soft-material-based implantable electrodes for medical applications, categorized according to their implantation site and material composition. We then review specific applications in three categories: neuroprosthetics, neural signal recording, and neuromodulation. Finally, we describe various strategies for the future development and application of implantable, soft-material-based devices.

A thin film polyimide mesh microelectrode for chronic epidural electrocorticography recording with enhanced contactability

OBJECTIVE

Epidural electrocorticography (ECoG) activity may be more reliable and stable than single-unit-activity or local field potential. Invasive brain computer interface (BCI) devices are limited by mechanical mismatching and cellular reactive responses due to differences in the elastic modulus and the motion of stiff electrodes. We propose a mesh-shaped electrode to enhance the contactability between surface of dura and electrode.

APPROACH

We designed a polyimide (PI) electrode with a mesh pattern for more conformal contact with a curved surface. We compared the contact capability of mesh PI electrodes with conventionally used sheet PI electrode. The electrical properties of the mesh PI electrode were evaluated for four weeks. We recorded the epidural ECoG (eECoG) activity on the surface of rhesus monkey brains while they performed a saccadic task for four months.

MAIN RESULTS

The mesh PI electrode showed good contact with the agarose brain surface, as evaluated by visual inspection and signal measurement. It was about 87% accurate in predicting the direction of saccade eye movement.

SIGNIFICANCE

Our results indicate that the mesh PI electrode was flexible and good contact on the curved surface and can record eECoG activity maintaining close contact to dura, which was proved by in vivo and in vitro test.