Needle-Type Ultra Micro Silver/Silver Chloride Reference Electrode for Use in Micro-Electrochemistry

Kitade, Tatsuya; Kitamura, Kazuya; Takegami, Shigehiko; Miyata, Yoko; Nagatomo, Miwa; Sakaguchi, Tomomi; Furukawa, Michiko

doi:10.2116/analsci.21.907

Cited by 22 publications

(16 citation statements)

References 11 publications

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“…Silver/silver chloride (Ag/AgCl) were chosen because they allow the free and reversible transport of ions from the buffer solution, resulting in little added impedance to the electrical circuit [88,89]. They are made by chloriding 125 µm silver wire (Goodfellow) in household bleach for several hours.…”

Section: Experimental Measurementsmentioning

confidence: 99%

Airflow Sensing With Arrays of Hydrogel Supported Artificial Hair Cells

Sarlo

Leo

2015

Volume 2: Integrated System Design and Implementation; Structural Health Monitoring; Bioinspired Smart Materials and Systems; E

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Arrays of fully hydrogel-supported, artificial hair cell (AHC) sensors based on bilayer membrane mechanotransduction are designed and characterized to determine sensitivity to multiple stimuli. The work draws upon key engineering design principles inspired by the characteristics of biological hair cells, primarily the use of slender hair-like structures as flow measurement elements. Many hair cell microelectromechanical (MEMS) devices to sense fluid flow have already been built based on this principle. However, recent developments in lipid bilayer applications, namely physically encapsulated bilayers and hydrogel interface bilayers, have facilitated the development of AHCs made primarily from biomolecular materials. The most current research in this field of "membrane based AHCs," shows promise, yet still lacks the modularity to create large sensor arrays similar to those in nature. This paper presents a novel bilayer based AHC platform, developed for array implementation by applying some of the core design principles of biological hair cells. These principles are translated into key design, fabrication and material considerations toward improved sensor sensitivity and modularity. Single hair cell responses to base excitation and short air pulses are to investigate the dynamic coupling between hair and bilayer membrane transducer. In addition, a spectral analysis of the AHC system under varying voltages and air flow velocities helps to build simple, predictive models for the sensitivity properties of the AHC. And finally, based on these results, we implement a spatial sensing strategy that involves mapping frequency content to stimulus location by "tuning" linear, three-unit arrays of AHCs.Individual AHC sensors characterization results demonstrate peak current outputs in the nanoamp range and measure flow velocities as high as 72 m/s. Characterization of the AHC response to base excitation and air pulses show that membrane current oscillates with the first three bending modes of the hair. Output magnitudes reflect of vibrations near the base of the hair. A 2 degree-of-freedom Rayleigh-Ritz approximation of the system dynamics yields estimates of 19 N/m and 0.0011 Nm/rad for the equivalent linear and torsional stiffness of the hair's hydrogel base, although double modes suggest non-symmetry in the gel's linear stiffness. The sensor output scales linearly with applied voltage (1.79 pA/V), avoiding a higher-order dependence on electrowetting effects. The free vibration amplitude of the sensor also increases in a linear fashion with applied airflow pressure (3.39 pA/m s −1 ). Array sensing tests show that the bilayers' consistent spectral responses allow for an accurate localization of the airflow source. However, temporal variations in bilayer size affect sensitivity properties and make airflow magnitude estimation difficult. The overall successful implementation of the array sensing method validates the sensory capability of the bilayer based AHC.iii DedicationTo my parents, Guillermo and Maria, and to my...

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Section: Experimental Measurementsmentioning

confidence: 99%

Airflow Sensing With Arrays of Hydrogel Supported Artificial Hair Cells

Sarlo

Leo

2015

Volume 2: Integrated System Design and Implementation; Structural Health Monitoring; Bioinspired Smart Materials and Systems; E

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“…Bilayer formation was characterized using electrical recordings via 125 µm-diameter silver-silver chloride (Ag/AgCl) wire-type electrodes [19] positioned in the aqueous phases on both sides of the bilayer. The data acquisition system (DAQ) was comprised of an AxoPatch 200B and Digidata 1440A (Molecular Devices) and run through AxoScope software (Molecular Devices).…”

Section: Materials and Equipmentmentioning

confidence: 99%

Formation, encapsulation, and validation of membrane-based artificial hair cell sensors

2012

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Hair cell structures are one of the most common forms of sensing elements found in nature. In nearly all vertebrates hair cells are used for auditory and vestibular sensing. In humans, approximately 16,000 auditory hair cells can be found in the cochlea of the ear. Each hair cell contains a stereocilia, which is the primary structure for sound transduction. This study looks to develop and characterize an artificial hair cell that resembles the stereocilia of the human ear. Recently our research group has shown that a single artificial hair cell can be formed in an open substrate using a single aqueous droplet and a hydrogel. In this study, air was blown across the hair and analyzed using spectral analysis. The results of this study provided the foundation for our current work toward an artificial hair cell that uses two aqueous droplets. In the current study a test fixture was created in order to consistently measure various properties of the encapsulated hair cell. The response of the hair cell was measured with an impulse input at various locations on the test fixture. A frequency response function was then created using the impulse input and the output of the sensor. It was found that the vibration of the hair was only detectable if the test fixture was struck at the correct location. By changing the physical parameters of the hair sensor, such as hair length, we were able to alter the response of the sensor. It was also found that the sensitivity of the sensor was reliant on the size of the lipid bilayer.

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“…They can, nevertheless, be of microscale. (26) They mostly utilise the all-important silver/silver chloride (Ag/ AgCl) electrode, which, in the presence of a high concentration of chloride ions, Cl − , can establish a very stable half-cell potential. For this reason, the Ag/AgCl electrode is used as a reference electrode in many other applications, including in a variety of microscale devices.…”

Section: Ag/agcl Reference Electrodementioning

confidence: 99%

“…An ultramicro Ag/AgCl reference electrode having a glass capillary tip outer diameter of 1.0 µm and inner diameter of 0.5±0.2 µm has been developed and its assessment for intracellular measurement reported. (26) A salt bridge was used to make contact between an internal 300-µm-diameter chlorided silver wire rather than fabricating a Ag microtip.…”

Section: Towards Nanoparticlesmentioning

confidence: 99%

Micro- and Nanosensors for Medical and Biological Measurement

Rolfe¹

2012

Sensors and Materials

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Micro-and nanosensors have evolved rapidly in the last few decades and they have expanding roles within biology and medicine, where measurement science and technology is of key importance. The targets for measurement include a huge number of simple and complex molecules, physical quantities such as pressure, force, displacement and flow, and electrical and magnetic phenomena arising from the heart, brain, muscles and nerves. Routine clinical care of patients currently benefits from the use of macro-and microscale sensors based on electrical, electrochemical, acoustic, piezoelectric and optical principles. Disposable electrodes for recording biopotentials, such as the electrocardiogram and electroencephalogram, are common, whereas invasive electrochemical and optical fibre sensors for pressure, blood gases and pH are useful in intensive care. Microscale immobilised enzyme glucose sensors are largely confined to the analysis of small blood samples, their invasive use still facing technical challenges. Sensors constructed to the nanoscale using quantum dots and carbon nanotubes are now rapidly emerging, being aimed at more complex biomolecules such as DNA. Nanoparticles in general and surface-enhanced Raman spectroscopy also play important roles in these developments. The impact of micro-and nanosensors on the fundamental understanding of major biomedical challenges and on clinical diagnosis and care are highlighted here.

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Needle-Type Ultra Micro Silver/Silver Chloride Reference Electrode for Use in Micro-Electrochemistry

Cited by 22 publications

References 11 publications

Airflow Sensing With Arrays of Hydrogel Supported Artificial Hair Cells

Airflow Sensing With Arrays of Hydrogel Supported Artificial Hair Cells

Formation, encapsulation, and validation of membrane-based artificial hair cell sensors

Micro- and Nanosensors for Medical and Biological Measurement

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