Recent Progress on Microelectrodes in Neural Interfaces

Abstract

Brain‒machine interface (BMI) is a promising technology that looks set to contribute to the development of artificial limbs and new input devices by integrating various recent technological advances, including neural electrodes, wireless communication, signal analysis, and robot control. Neural electrodes are a key technological component of BMI, as they can record the rapid and numerous signals emitted by neurons. To receive stable, consistent, and accurate signals, electrodes are designed in accordance with various templates using diverse materials. With the development of microelectromechanical systems (MEMS) technology, electrodes have become more integrated, and their performance has gradually evolved through surface modification and advances in biotechnology. In this paper, we review the development of the extracellular/intracellular type of in vitro microelectrode array (MEA) to investigate neural interface technology and the penetrating/surface (non-penetrating) type of in vivo electrodes. We briefly examine the history and study the recently developed shapes and various uses of the electrode. Also, electrode materials and surface modification techniques are reviewed to measure high-quality neural signals that can be used in BMI.

Biointegrated and Wirelessly Powered Implantable Brain Devices: A Review

“…Recent advancement in the microelectronics manufacturing promoted the development of patterned, micromachined, and rigid probes [46]. Nowadays, the state-of-the-art devices like Michigan-style probes [47] and Utah arrays [48] are commercially available and has been utilized in neuroscience research. Furthermore, emerging Silicon-based implantable probe technologies such as Neuropixels for high-density neural recordings [49], multifunctional probe [50], as well as 3D probe for recording of coordinated brain activity from large population of neurons [51] have enriched us with new insights to study the brain.…”

The rise of flexible electronics in neuroscience, from materials selection to in vitro and in vivo applications

“…Indeed, stiffness mismatch between the brain tissue and the probe substrate represents the main cause of implant failure. Brain is relatively soft with a Young's Modulus of few kPa, while even flexible MEAs based on polyimide, SU-8 or Parylene are in the range of few GPa [10]. Conversely, soft polymers like PDMS show similar brain stiffness but result difficult to handle and cannot be easily manufactured in ultra-thin layers.…”

“…Numerous review papers reported new findings in the part that is usually in contact with the brain, such as the electrode grid [10][11][12][13] and described physiological mechanisms underlying the implantation of these devices in the brain [14], but very few present all the fabrication methodologies that involve new materials and electronic design to allow the manufacturing of the whole system.…”

Flexible Micropillar Electrode Arrays for In Vivo Neural Activity Recordings

“…Subdural electrodes are much less invasive than penetrating depth electrodes that cause tissue damage and elicit pronounced foreign body response . At the same time, subdural electrodes can record neural activity with higher temporal and spatial resolution than scalp electrodes because of their close proximity to neural tissues . For these reasons, subdural ECoG recordings have also been considered as an attractive candidate to build next‐generation brain‐machine interface (BMI) …”

“…The interfaces between electrodes and neural tissues play an essential role in neural activity recordings because extracellular signals decay rapidly with distance . A key challenge for creating tight interfaces between conventional subdural electrodes and neural tissues has been their large mechanical mismatch .…”