Enhanced visible light-excited ZnSnO3 for room temperature ppm-level CO2 detection

The electroencephalogram (EEG) is considered to be a promising method for studying brain disorders. Because of its non-invasive nature, subjects take a lower risk compared to some other invasive methods, while the systems record the brain signal. With the technological advancement of neural and material engineering, we are in the process of achieving continuous monitoring of neural activity through wearable EEG. In this article, we first give a brief introduction to EEG bands, circuits, wired/wireless EEG systems, and analysis algorithms. Then, we review the most recent advances in the interfaces used for EEG recordings, focusing on hydrogel-based EEG electrodes. Specifically, the advances for important figures of merit for EEG electrodes are reviewed. Finally, we summarize the potential medical application of wearable EEG systems.

Design of hydrogel-based wearable EEG electrodes for medical applications.

The detection of carbon dioxide (CO2) and water molecules (H2O) is of great interest because they play an important role in the fields of industry, agriculture, climate and medical treatment. However, both experimental studies and engineering applications indicate that most CO2 sensors suffer from selectivity problems in high humidity. Herein, we detect concentrations of CO2 and H2O simultaneously through decoupling surface density and shear modulus under negligible effect of electric conductivity based on a surface acoustic wave (SAW) resonator at 221 MHz. The SAW-based sensor demonstrates a small measurement error of ~ 65 ppm in CO2 and ~ 1.2% RH in H2O. The sensor also shows excellent short-term stability of 0.8 kHz. Besides, this general method that using a single SAW resonator to detect two analytes selectively will be useful for other resonator-based sensors.

Selective Detection of CO2 and H2O Dual Analytes Through Decoupling Surface Density and Shear Modulus Based on Single SAW Resonator

Highly sensitive, flexible and transparent TiO2/nanocellulose humidity sensor for respiration and skin monitoring

• A highly sensitive balloon-like fiber interferometer based on GO nanomaterial coated for humidity measurement is proposed. • GO nanomaterials are coated in the sensing region of balloon-like fiber interferometer by physical deposition method. • An RH sensor based on balloon-like fiber structure interferometer is fabricated. • The sensor possesses good repeatability and stability, and offers broad application prospects for RH monitoring. A highly sensitive balloon-like fiber interferometer based on Graphene Oxide (GO) nanomaterial coated for humidity measurement is proposed in this paper. The Mach-Zehnder interferometer (MZI) is formed by bending single-mode optical fiber. Then GO nanomaterials, which are sensitive to environmental humidity, are coated in the sensing region of the balloon-like fiber interferometer by physical deposition method. When ambient environmental relative humidity (RH) changes, GO nanomaterials will interact with water molecules, thus changing the refractive index (RI) around the sensing region of the balloon-like fiber interferometer, resulting in the shift of resonant wavelength. The measurement of different RH in the environment can be realized by evaluating the spectral drift. By comparing the RH sensitivity of the balloon-like fiber structure with different sensitive lengths, it can be found that the RH sensitivity of the balloon-like fiber structure is enhanced with the increase of the sensitive length. The experimental results of thickness optimization show that when the thickness of GO nanomaterial coating is about 250 nm, the sensitivity of 0.449 nm/%RH with a linearity of 0.992 can be achieved in the range of low humidity (less than 50 %RH). The response time and recovery time are about 4.8 s and 7.8 s. Moreover, the temperature sensitivity of the sensing structure with 250 nm GO nanomaterial is 0.102 nm/°C. Compared with the sensing structure without GO nanomaterial, the cross-influence of temperature can be effectively reduced by GO nanomaterial coating, so as to be better applied to humidity measurement. The balloon-like fiber sensors coated with GO nanomaterial possess good repeatability and stability, and offer broad application prospects for RH monitoring such as in the fields of biochemistry and medicine in the future. 

Renata Silva

Papers

Boron and nitrogen co-doped vertical graphene electrodes for scalp electroencephalogram recording

Surface acoustic wave sensor based on Au/TiO2/PEDOT with dual response to carbon dioxide and humidity

Surface acoustic wave sensor based on Au/TiO2/PEDOT with dual response to carbon dioxide and humidity.

Synthesis of PVDF membrane loaded with wrinkled Au NPs for sensitive detection of R6G