Xuhong Guo

A Motion Interference-Insensitive Flexible Dry Electrode

Objective: A novel dry electrode is developed to improve the comfortability and the capability of alleviating motion interference by combining microneedles array (MNA) with flexible substrate. Methods: Silicon MNA with sharp tips and limited height is fabricated and transferred ona flexible Polydimethylsiloxane (PDMS) substrate through bonding. Poly (3, 4-ethylenedioxy thiophene) doped with poly (styrenesulfonate) (PEDOT/PSS) is coated on the surface of flexible MNA to form a conductive layer. Results: Flexible dry electrode with 1.2 cm diameter is successfully fabricated. The mean impedance magnitudes (measured on skin) at 10 Hz are 61.2 ± 31.3 kΩ·cm2 for flexible dry electrode, while the values are 114.9 ± 36.1 kΩ·cm2 for wet electrode and 335.7 ± 110.5 kΩ·cm2 for flexible planar dry electrode, respectively. In the process of biopotential recording, the flexible dry electrode has the similar performance as that of wet electrode. It exhibits more stable recording stability than rigid dry electrode in the movement state. Conclusion: By integrating flexible PDMS substrate, sharp and hard MNA structure, as well as PEDOT/PSS coated surface together, a novel dry electrode is developed to meet the comfortable and antimotion interference requirement of wearable equipment. Significance: The novel flexible dry electrode provides a simple and comfortable method to record biopotential signals in daily life.

Skin-Potential Variation Insensitive Dry Electrodes for ECG Recording

Objective: A skin-potential variation (SPV) insensitive dry electrode is developed to remove the interference of SPV. Methods: Based on a conventional microneedles array-based electrode, a layer of Parylene membrane is coated at the root of microneedles to insulate the electrode from the corneum layer. Only tips of the needles are exposed to make it can contact with the stratum germinativum layer directly. Results: As a result, skin potential will not be coupled into the recording electrode. Thus, SPV will not influence the biopotential recording in the dynamic state. Conclusion: The proposed electrode is potential for a device which is insensitive to the motion noise source from SPV. Significance: It paves the way for applications of the proposed dry electrode in the wearable technology which require strong anti-motion interference ability.

Developing a one-channel BCI system using a dry claw-like electrode

An eight-class SSVEP-based BCI system was designed and demonstrated in this study. To minimize the complexity of the traditional equipment and operation, only one work electrode was used. The work electrode was fabricated in our laboratory and designed as a claw-like structure with a diameter of 15 mm, featuring 8 small fingers of 4mm length and 2 mm diameter, and the weight was only 0.1g. The structure and elasticity can help the fingers pass through the hair and contact the scalp when placed on head. The electrode was capable to collect evoked brain activities such as steady-state visual evoked potentials (SSVEPs). This study showed that although the amplitude and SNR of SSVEPs obtained from a dry claw electrode was relatively lower than that from a wet electrode, the difference was not significant. This study further implemented an eight-class SSVEP-based BCI system using a dry claw-like electrode. Three subjects participated in the experiment. Using infinite impulse response (IIR) filtering and a simplified threshold method based on fast Fourier transform (FFT), the average accuracy of the three participants was 89.3% using 4 sec-long SSVEPs, leading to an average information transfer rate (ITR) of 26.5 bits/min. The results suggested the ability of using a dry claw-like electrode to perform practical BCI applications.An eight-class SSVEP-based BCI system was designed and demonstrated in this study. To minimize the complexity of the traditional equipment and operation, only one work electrode was used. The work electrode was fabricated in our laboratory and designed as a claw-like structure with a diameter of 15 mm, featuring 8 small fingers of 4mm length and 2 mm diameter, and the weight was only 0.1g. The structure and elasticity can help the fingers pass through the hair and contact the scalp when placed on head. The electrode was capable to collect evoked brain activities such as steady-state visual evoked potentials (SSVEPs). This study showed that although the amplitude and SNR of SSVEPs obtained from a dry claw electrode was relatively lower than that from a wet electrode, the difference was not significant. This study further implemented an eight-class SSVEP-based BCI system using a dry claw-like electrode. Three subjects participated in the experiment. Using infinite impulse response (IIR) filtering and a simplified threshold method based on fast Fourier transform (FFT), the average accuracy of the three participants was 89.3% using 4 sec-long SSVEPs, leading to an average information transfer rate (ITR) of 26.5 bits/min. The results suggested the ability of using a dry claw-like electrode to perform practical BCI applications.

A sapphire based monolithic integrated optrode

A novel kind of optrode fabricated on a sapphire substrate is proposed for optogenetic applications in neuroscience. Eight thin-film neural electrodes and a GaN-LED are monolithically integrated on the surface of a sapphire shank. The LED is used for optogenetic stimulation and the multiple electrodes are used for simultaneous recording of neural activities. The output power density of the LED is 1-19 mW/mm2 at 468 nm, driving with a current from 0.7-10 mA. The mean electrochemical impedance of the eight recoding sites on the optrode at 1 kHz is 385 kΩ. The highest temperature-raise at tissue around the LED is almost 1 °C when the output power density is 3 mw/mm2. The monolithic integrated structure will make it a powerful tool for optogenetics.A novel kind of optrode fabricated on a sapphire substrate is proposed for optogenetic applications in neuroscience. Eight thin-film neural electrodes and a GaN-LED are monolithically integrated on the surface of a sapphire shank. The LED is used for optogenetic stimulation and the multiple electrodes are used for simultaneous recording of neural activities. The output power density of the LED is 1-19 mW/mm2 at 468 nm, driving with a current from 0.7-10 mA. The mean electrochemical impedance of the eight recoding sites on the optrode at 1 kHz is 385 kΩ. The highest temperature-raise at tissue around the LED is almost 1 °C when the output power density is 3 mw/mm2. The monolithic integrated structure will make it a powerful tool for optogenetics.

A High-Speed SSVEP-Based BCI Using Dry EEG Electrodes

A high-speed steady-state visual evoked potentials (SSVEP)-based brain-computer interface (BCI) system using dry EEG electrodes was demonstrated in this study. The dry electrode was fabricated in our laboratory. It was designed as claw-like structure with a diameter of 14 mm, featuring 8 small fingers of 6 mm length and 2 mm diameter. The structure and elasticity can help the fingers pass through the hair and contact the scalp when the electrode is placed on head. The electrode was capable of recording spontaneous EEG and evoked brain activities such as SSVEP with high signal-to-noise ratio. This study implemented a twelve-class SSVEP-based BCI system with eight electrodes embedded in a headband. Subjects also completed a comfort level questionnaire with the dry electrodes. Using a preprocessing algorithm of filter bank analysis (FBA) and a classification algorithm based on task-related component analysis (TRCA), the average classification accuracy of eleven participants was 93.2% using 1-second-long SSVEPs, leading to an average information transfer rate (ITR) of 92.35 bits/min. All subjects did not report obvious discomfort with the dry electrodes. This result represented the highest communication speed in the dry-electrode based BCI systems. The proposed system could provide a comfortable user experience and a stable control method for developing practical BCIs.