A microneedle electrode array on flexible substrate for long-term EEG monitoring

137

Bioelectrical or electrophysiological signals generated by living cells or tissues during daily physiological activities are closely related to the state of the body and organ functions, and therefore are widely used in clinical diagnosis, health monitoring, intelligent control and human-computer interaction. Ag/AgCl electrodes with wet conductive gels are widely used to pick up these bioelectrical signals using electrodes and record them in the form of electroencephalograms, electrocardiograms, electromyography, electrooculograms, etc. However, the inconvenience, instability and infection problems resulting from the use of gel with Ag/AgCl wet electrodes can’t meet the needs of long-term signal acquisition, especially in wearable applications. Hence, focus has shifted toward the study of dry electrodes that can work without gels or adhesives. In this paper, a retrospective overview of the development of dry electrodes used for monitoring bioelectrical signals is provided, including the sensing principles, material selection, device preparation, and measurement performance. In addition, the challenges regarding the limitations of materials, fabrication technologies and wearable performance of dry electrodes are discussed. Finally, the development obstacles and application advantages of different dry electrodes are analyzed to make a comparison and reveal research directions for future studies.

Section: Invasive Microneedle Electrodesmentioning

confidence: 99%

Dry Electrodes for Human Bioelectrical Signal Monitoring

Zhao

Dong

et al. 2020

137

“…Therefore, it is important to develop special electrodes for wearable bio-signal monitoring in home health care. Usually, Ag/AgCl electrodes are widely used in clinical practice, which require skin preparation and the use of gel [ 2 , 3 , 4 ]. The gel may cause skin irritations and allergic reactions, and gets dry during monitoring, reducing the quality of the recorded signals [ 5 , 6 ].…”

Section: Introductionmentioning

confidence: 99%

“…LDW is a promising process for the easy fabrication of conductive patterns due to it being high resolution, maskless, low-cost and easy to manipulate. Various methods have been employed to fabricate microneedle arrays, including etching and lithography [ 4 , 21 , 22 , 23 , 24 , 25 ], laser machining [ 26 , 27 , 28 ], micro-molding [ 29 , 30 , 31 ], 3D printing [ 32 ], thermal drawing [ 33 ], and magnetization-induced self-assembly [ 34 , 35 ], but most of microneedle arrays were fabricated on the rigid substrates. These techniques cannot directly fabricate microneedle arrays on a flexible substrate.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Flexible Microneedle Array Electrodes for Wearable Bio-Signal Recording

Ren

Gao

et al. 2018

Laser-direct writing (LDW) and magneto-rheological drawing lithography (MRDL) have been proposed for the fabrication of a flexible microneedle array electrode (MAE) for wearable bio-signal monitoring. Conductive patterns were directly written onto the flexible polyethylene terephthalate (PET) substrate by LDW. The microneedle array was rapidly drawn and formed from the droplets of curable magnetorheological fluid with the assistance of an external magnetic field by MRDL. A flexible MAE can maintain a stable contact interface with curved human skin due to the flexibility of the PET substrate. Compared with Ag/AgCl electrodes and flexible dry electrodes (FDE), the electrode–skin interface impedance of flexible MAE was the minimum even after a 50-cycle bending test. Flexible MAE can record electromyography (EMG), electroencephalography (EEG) and static electrocardiography (ECG) signals with good fidelity. The main features of the dynamic ECG signal recorded by flexible MAE are the most distinguishable with the least moving artifacts. Flexible MAE is an attractive candidate electrode for wearable bio-signal monitoring.

“…Specifically, the Ag/AgCl electrode suffers from two major defects, namely skin preparation and the use of gel. A microneedle array electrode is a promising dry electrode that has attracted increasing attention in EII [ 11 ], ECG [ 12 ], EMG [ 13 ], and EEG [ 14 ] monitoring due to excellent properties including painless puncture without skin preparation, minimal skin trauma, reduced infection, ease of operation, and high selectivity [ 15 , 16 ]. The previous microneedle array electrode mainly focused on the bio-signals recording.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Composite Microneedle Array Electrode for Temperature and Bio-Signal Monitoring

Sun

Ren

Jiang

et al. 2018

Body temperature and bio-signals are important health indicators that reflect the human health condition. However, monitoring these indexes is inconvenient and time-consuming, requires various instruments, and needs professional skill. In this study, a composite microneedle array electrode (CMAE) was designed and fabricated. It simultaneously detects body temperature and bio-signals. The CMAE consists of a 6 × 6 microneedles array with a height of 500 μm and a base diameter of 200 μm. Multiple insertion experiments indicate that the CMAE possesses excellent mechanical properties. The CMAE can pierce porcine skin 100 times without breaking or bending. A linear calibration relationship between temperature and voltage are experimentally obtained. Armpit temperature (35.8 °C) and forearm temperature (35.3 °C) are detected with the CMAE, and the measurements agree well with the data acquired with a clinical thermometer. Bio-signals including EII, ECG, and EMG are recorded and compared with those obtained by a commercial Ag/AgCl electrode. The CMAE continuously monitors bio-signals and is more convenient to apply because it does not require skin preparation and gel usage. The CMAE exhibits good potential for continuous and repetitive monitoring of body temperature and bio-signals.