An analytic equation for single cell electrochemical impedance spectroscopy with a dependence on cell position

An analytic equation for electrochemical impedance of a single-cell measured with a microelectrode is presented. A previously reported equation had a practical problem that it is valid only when the microelectrode resides at the center of the cell under test. In this work, we propose a new analytic equation incorporating dependence on cell position, and confirmed its effectiveness by numerical simulation. Comparisons show that our proposed equation gives an excellent agreement with simulated impedance values. Discrepancies between results from our equation and numerical simulation is suppressed within 13%, which is a dramatic reduction from the previously-reported equation as large as 58%. The proposed analytic equation is expected to enable more accurate analysis in actual cell experiments.Comment: 31 pages, 8 figures, journal manuscrip

Electrochemical Redox Cycling Realized by Chromatography Paper-based Sensor

In this work, we demonstrated that enhancement of electrochemical current due to redox cycling could be accomplished by paper-based biosensor without any expensive micro-fabrication process. The paper-based sensor had layered structure to generate higher current than a conventional one. We took advantage of the fact that the paper thickness was micrometer-sized (180um), and it defined the distance between two electrochemical electrodes on both sides of the paper. Experimental results showed signatures of the redox cycling, where the electrochemical current from low concentration molecules could be arbitrarily increased by decreasing the distance between electrodes. Such a structure was advantageous for detecting target molecules at very low concentration, proposing a low-cost highly-sensitive biochemcal sensor.

Potentiometric Glucose Detection by Paper-based Electrochemical Sensor on CMOS Chip

This paper presents a low cost portable medical device for biochemical sensor using CMOS chip and paper-based fluidic channel. We measured a potential produced by enzyme activity of glucose between the working and reference electrode on CMOS chip. A liquid sample is transported by paper-based fluidic channel, which is made of chromatography paper and silicone resin, and consists of the area for filtering a sample (filter layer) and that for reacting enzyme (enyzme layer). The paper-based fluidic channel is used by combining CMOS chip, and the solution with glucose is dropped from top of the paper-based fluidic channel. The concentrations of glucose are detected by potentiometry (open circuit potential time). The experimental results show that the glucose concentration is measured by CMOS chip and paper-based fluidic channel

Simultaneous Electrochemical Measurement using Paper Fluidic Channel on CMOS Chip

This paper described the new system of biosensing using CMOS chip. The system was expected to be used in various circumstances because it was suitable for miniaturization compared to the conventional system. To conduct electrochemical measurements, the new system used paper fluidic channel set on the CMOS chip to transport solution to the on-chip electrodes. The materials of paper fluidic channel were only paper and silicone resin, and these were biocompatible. In experiment, we carried out simultaneous detection of glucose and ethanol in liquid sample solutions on the 5mm square CMOS chip and paper fluidic channel. Furthermore, this system can detect various target molecules in addition to glucose and ethanol, and increase number of simultaneous measurement by adding some more process to the paper and CMOS chip.

Sum Rules and Universality in Electron-modulated Acoustic Phonon Interaction in a Free-standing Semiconductor Plate

Analysis of acoustic phonons modulated due to the surfaces of a free-standing semiconductor plate and their deformation-potential interaction with electrons are presented. The form factor for electron-modulated acoustic phonon interaction is formulated and analyzed in detail. The form factor at zero in-plane phonon wave vector satisfies sum rules regardless of electron wave function. The form factor is larger than that calculated using bulk phonons, leading to a higher scattering rate and lower electron mobility. When properly normalized, the form factors lie on a universal curve regardless of plate thickness and material

Theory of quasiballistic transport through nanocrystalline silicon dots

A model to describe the underlying physics of high-energy electron emission from a porous silicon diode is presented. The model is based on an atomistic tight-binding method combined with semiclassical Monte Carlo simulation. It well reproduces essential features of experimental findings. An initial acceleration region is shown to play a crucial role in generating quasiballistic electron emission

Portable Electrochemical Gas Sensing System with a Paper-Based Enzyme Electrode

An unconventional portable electrochemical gas sensor composed of a smartphone, a finger-sized sensing chip and a single use paper-based enzyme electrode was proposed to detect a particular target gaseous inclusion for self-breath-analysis with ease. This attempt allowed us to monitor our physical status immediately and continuously regardless of a time, place or person due to the improved convenience, immediacy, and affordability. The custom CMOS chip with the capability of performing an amperometric determination when the power voltage supplied from the earphone jack of a smartphone was designed as an analytical device. A disposable enzyme electrode was prepared simply from a chromatography paper and a commercial carbon pencil instead of the conventional indisposable material and complex manufacturing process. The quantification of ethanol in gaseous samples was demonstrated in range from 50 to 500ppm (V/V) in accord with concentrations in exhaled breath. The response current increased linearly with increasing vapor ethanol concentration