Development of fabric electrode for bio-potential signal acquisition in wearable health monitoring and effect of perspiration on signal acquisition

Development of a gel-free bio-potential electrode for the wearable health monitoring applications is a challenging goal. A conductive fabric electrode can replace the traditional conductive gel electrode. This paper describes the development of a conductive fabric electrode with regard to its potential use for electrocardiogram (ECG) acquisition. Since direct contact between the conductive fabric and human skin will be involved, an investigation on the effect of perspiration on the electrical conductivity of fabric is critical. Hence, the developed electrode was treated with alkaline (pH=8.0) and acidic (pH=4.3) perspiration for 3, 8 and 40 h to study the effect of perspiration on the conductivity and surface morphology. The acquired ECG signals were analysed with respect to morphology and frequency distribution. Conductivity tests were carried out on the perspiration-treated test electrodes by two probe method and surface resistivity meter. The ECG signals of volunteers were also recorded. The results showed a slight decrease in conductivity but without affecting the morphology and the quality of ECG signal. Leached silver content in the acid perspiration-treated solution was found to be 0.117 ppm as determined by Atomic absorption spectroscopy. The result shows that soft conducting textile materials can indeed be used as an electrode for ECG acquisition. This is a novel type of gel-free fabric electrode for long term wearable health monitoring applications including space application.

PPy coated nanoflower like CuCo2O4 based on in situ growth of nanoporous copper for high-performance supercapacitor electrodes

General CuCo2O4 electrodes suffer a very low reversible capacity and poor cycling stability because of easily fading phenomena and volume change during cycling. To optimize the electrode, a facile method is conducted to fabricate a novel electrode of Cu@CuCo2O4@polypyrrole (Cu@CCOP) nanoflowers. Due to larger specific surface area and more electrochemical reactive areas of Cu@CCOP nanoflowers, the pseudocapacitance of the in-situ grown Cu@CCOP (912 F g-1 at 2 A g-1) is much higher than the pristine CuCo2O4 (CCO) (618 F g-1 at 2 A g-1). Remarkably, the Cu@CCOP (cathode) and active carbon (anode) are used to assemble an asymmetric supercapacitor, which exhibits a relatively high energy density of 90 Wh kg-1 at a power density of 2519 W kg-1 and 35 Wh kg-1 at a high-power density of 9109 W kg-1, and excellent cycling stability (about 90.4% capacitance retention over 10000 cycles). The prominent performance of Cu@CCOP makes it as a potential electrode for supercapacitor.

Fabrication of GeS-graphene composites for electrode materials in lithium-ion batteries

The new electrode materials are critically important for the development of lithium-ion batteries (LIBs). Herein, we report the synthesis of GeS-graphene composite (GeS-G) by facile sonication which exhibits the excellent cycling performance for lithium-ion batteries. Under the condition of change-discharge rate of 50 mA·g-1 and voltage window of 0.005-3 V, the specific capacity of GeS-G is 170 mAh·g-1 after 100 cycles, which is significantly higher than that of pure GeS. The results of the present work imply that the nanostructure of GeS-G is the potential electrode materials for application in high-performance lithium-ion batteries and enrich the gene bank of lithium-ion battery materials.

Cross-Borehole DC Resistivity Tomography of Sea Ice: Temporal and Spatial Variations in the Anisotropic Microstructure

<p>As an inhomogeneous mixture of pure ice, brine, air and solid salts the physical properties of sea ice depend on its highly temperature-dependent microstructure. Understanding the microstructure and the way it responds to variations in temperature and salinity is crucial in developing an improved understanding of the interaction between sea ice and the environment. However, measurements monitoring the microstructure of sea ice are difficult to obtain without disturbing its natural state. The brine fraction of sea ice is orders of magnitude more conductive than the solid ice, thus direct current resistivity techniques should yield information on sea ice microstructure. Due to the preferential vertical alignment of brine inclusions, the bulk resistivity of first-year sea ice is anisotropic, complicating interpretation of surface resistivity soundings. However, it can be shown that in a bounded anisotropic medium the resistivity structure may be resolved through in situ cross-borehole measurements. Measurement between borehole pairs, each containing one current and one potential electrode, allows the determination of the horizontal component of the anisotropic bulk resistivity (PH). Using three to four electrodes positioned at approximately the same depth in separate boreholes, provides an under-estimation of the geometric mean resistivity (Pm), and numerical modelling is required to retrieve an estimate of the true Pm. Combining these resistivities allows calculation of the vertical component of the bulk resistivity (PV). This thesis looks at results from measurements made in first year sea ice in April – June 2008 off Barrow, Alaska and in November 2009 off Ross Island, Antarctica. At Barrow, relatively quiescent conditions typically lead to a predominance of columnar ice, while more turbulent conditions and underwater ice formation in McMurdo Sound tend to produce a larger component of frazil or platelet ice. Interpretation of the resistivity measurements, aided by temperature and salinity data, shows that this measurement technique can be used to observe evolution of the ice structure, and distinguish different ice types. Basic two phase structures provide a simple picture of the brine microstructure and how it changes with depth and time. These models indicate the need for vertical connectivity of the brine inclusions even in cool ice, and that PH seems to be mostly due to connections along grain boundaries.</p>

Cross-Borehole DC Resistivity Tomography of Sea Ice: Temporal and Spatial Variations in the Anisotropic Microstructure

<p>As an inhomogeneous mixture of pure ice, brine, air and solid salts the physical properties of sea ice depend on its highly temperature-dependent microstructure. Understanding the microstructure and the way it responds to variations in temperature and salinity is crucial in developing an improved understanding of the interaction between sea ice and the environment. However, measurements monitoring the microstructure of sea ice are difficult to obtain without disturbing its natural state. The brine fraction of sea ice is orders of magnitude more conductive than the solid ice, thus direct current resistivity techniques should yield information on sea ice microstructure. Due to the preferential vertical alignment of brine inclusions, the bulk resistivity of first-year sea ice is anisotropic, complicating interpretation of surface resistivity soundings. However, it can be shown that in a bounded anisotropic medium the resistivity structure may be resolved through in situ cross-borehole measurements. Measurement between borehole pairs, each containing one current and one potential electrode, allows the determination of the horizontal component of the anisotropic bulk resistivity (PH). Using three to four electrodes positioned at approximately the same depth in separate boreholes, provides an under-estimation of the geometric mean resistivity (Pm), and numerical modelling is required to retrieve an estimate of the true Pm. Combining these resistivities allows calculation of the vertical component of the bulk resistivity (PV). This thesis looks at results from measurements made in first year sea ice in April – June 2008 off Barrow, Alaska and in November 2009 off Ross Island, Antarctica. At Barrow, relatively quiescent conditions typically lead to a predominance of columnar ice, while more turbulent conditions and underwater ice formation in McMurdo Sound tend to produce a larger component of frazil or platelet ice. Interpretation of the resistivity measurements, aided by temperature and salinity data, shows that this measurement technique can be used to observe evolution of the ice structure, and distinguish different ice types. Basic two phase structures provide a simple picture of the brine microstructure and how it changes with depth and time. These models indicate the need for vertical connectivity of the brine inclusions even in cool ice, and that PH seems to be mostly due to connections along grain boundaries.</p>

Theoretical investigation of capacitances in functionalized MXene supercapacitors Mn+1CnO2,M=Ti,V,Nb,Mo

MXene, the class of two-dimensional materials, has been found to be useful as potential electrode materials for electrochemical capacitors. Although experimental investigation on the electrochemical performances of a few MXenes have been carried out with exciting results, a complete understanding of their atomic scale behaviour is yet to be done. Using first-principles electronic structure methods, we perform a systematic investigation of the capacitances in pristine and functionalised MXenes Mn+1CnO2 where M = T i, V, Nb and Mo. We provide results on each of the three sources of the capacitance and analyse them in detail for a complete understanding of their behaviour. The inter-pretation of the experimental results, wherever available, in the light of our computations,provides useful insights.