Electrochemical Characteristics Based on Skin-Electrode Contact Pressure for Dry Biomedical Electrodes and the Application to Wearable ECG Signal Acquisition

Based on one simulated skin-electrode electrochemical interface, some electrochemical characteristics based on skin-electrode contact pressure (SECP) for dry biomedical electrodes were analysed and applied in this research. First, 14 electrochemical characteristics including 2 static impedance (SI) characteristics, 11 alternating current impedance (ACI) characteristics and one polarization voltage (PV), and 4 SECP characteristics were extracted in one electrochemical evaluation platform, and their correlation trends were statistically analysed. Second, dry biomedical electrode samples developed by the company and the laboratory, including textile electrodes, Apple watch, AMAZFIT rice health bracelet 1S, and stainless steel electrodes, were placed horizontally and vertically on the “skin” surface of the electrochemical evaluation platform, whose polarization voltages were quantitatively analysed. Third, electrocardiogram (ECG) collection circuits based on an impedance transformation (IT) circuit for textile electrodes were designed, and a wearable ECG acquisition device was designed, which could obtain complete ECG signals. Experimental results showed SECP characteristics for dry electrodes had good correlations with static impedance and ACI characteristics and the better correlation values among 2-10 Hz. In addition, polarization voltages in vertical state were smaller in horizontal state for dry biomedical electrodes, and polarization voltage of electrode pair (PVEP) values for Apple watch bottom was always smaller than ones for Apple watch crown and LMF-2 textile electrode. And the skin-electrode contact impedance of IT textile electrodes was less than the traditional textile electrodes.

Polarization Reversal Characteristics in Capacitors with a Metal/Insulator/Ferroelectric/Metal Structure

A metal/insulator/ferroelectric/metal structure was fabricated using a covering of approximately 10 nm thick of an insulating polystyrene film on a ferroelectric poly(vinylidene fluoride-trifluoroethylene) film. To fabricate several samples, the thickness of the ferroelectric film was held constant while the thickness of the insulating film was varied from 8 to 24 nm. The polarization– voltage relationships were measured to extract the main parameters, in this case the remanent polarization, depolarization, coercive voltage and biased voltage values. As the insulating film becomes thicker, the remanent polarization and coercive voltage values tended to increase. On the other hand, depolarization and biased voltage values decreased. By analyzing the above mentioned parameters, a certain optimum insulator thickness could be predicted. This work shows that metal/insulator/ferroelectric/metal devices are more useful than metal/ferroelectric/metal capacitors.

INDUCTIVE SOURCE INDUCED POLARIZATION OF FROZEN ROCKS AND ITS RELATIONSHIP WITH DIELECTRIC RELAXATION OF ICE

Fast decaying induced polarization in frozen rocks manifest itself as a not monotone induction transients. To account for induced polarization in the transient electromagnetic method, one usually uses the Pelton resistivity model. The relaxation time t, as found using the Pelton model, determines the decay rate of induced polarization voltage response to a current source. Conversion from t to the time constant t specifying the decay rate of the polarization current response to a voltage source, suggests that fast decaying induced polarization in frozen rocks is controlled by the dielectric relaxation of ice.

Effect of Buffer Layer Capacitance on the Electrical Characteristics of Ferroelectric Polymer Capacitors and Field Effect Transistors

We demonstrated the effect of a buffer layer on the electrical characteristics of ferroelectric polymer capacitors and field-effect transistors. Various polymer materials with a dielectric constant between 2 and 42 were used to form buffer layers with a similar thicknesses, but with different capacitances. In order to evaluate the characteristics of the ferroelectrics with a buffer layer, the polarization–voltage characteristics of the capacitor, the transfer characteristics, and the retention characteristics of the transistors were investigated. As the capacitance of the buffer layer increased, high remnant polarization (Pr), high hysteresis, and long retention times were observed. Exceptionally, when poly(methylmethacrylate) and rigid poly(aryl ether) (poly(9,9-bis(4-hydroxyphenyl)fluorene-co-decafluorobiphenyl)) were used as the buffer layer, Pr had a value close to 0 in the dynamic measurement polarization–voltage (P–V) characteristic, but the quasi-static measurement transfer characteristic and the static measurement retention characteristic showed relatively high hysteresis and long retention times. Our study provides a scientific and technical basis for the design of ferroelectric memory and neuromorphic devices.

Al Ions Doping Effect on The Diffusion Coefficient and Capacity of Li4Ti5O12 (Lithium Titanate, LTO) in Lithium-Ion Battery Anode

Li4Ti5O12 (LTO) anode doped with Al ions with varying concentrations (Al = 0; 0.005; 0.015; 0.03; 0.045) was successfully synthesized using the sol-gel method. Al-doped LTO samples were obtained through the sintering of gel at 850oC for 4 hours under a normal atmosphere. Electrochemical performance such as charge-discharge capacity and diffusion coefficient were characterized using an automatic battery cycler. The cells consist of electrode sheets (LTO doping Al) as a working electrode, lithium metal as the counter electrode, Celgard film as the separator, and LiPF6 as an electrolyte. Cyclic voltammetry test results show that a greater scan rate results in decreased capacity and greater polarization voltage. In addition, an increase in concentrations used in Al doping on LTO causes capacity, and the diffusion coefficient tends to decrease.