Frequency response of electrochemical sensors to hydrodynamic fluctuations

Deslouis, C.; Gil, O.; Tribollet, Bernard

doi:10.1017/s0022112090002567

Cited by 87 publications

(53 citation statements)

References 20 publications

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“…Determining the transfer function has been the objective of several studies (Deslouis et al 1990;Nakoryakov et al 1986). This function allows identifying wall shear stress dynamics.…”

Section: Electrodiffusion Technique For Wall Shear Rate Determinationmentioning

confidence: 99%

Unsteady flows in milli- and microsystems: analysis of wall shear rate fluctuations

Huchet¹,

Legentilhomme

Legrand

et al. 2011

Exp Fluids

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To cite this version:Abstract The particular benefits of microfluidic systems, in terms of heat and mass transfer enhancement, require conducting local flow diagnostics, especially when unsteady properties of the microflow can play a critical role at the reaction interface, as currently observed in the fields of bioengineering and chemical engineering. The present paper focuses on unsteady confined flows within microsystems characterized by various geometries of crossing channels and exhibiting high surface-to-volume ratios. An experimental analysis of the signal measured at microsensors embedded to the wall of microsystems is discussed. In the objective of performing flow diagnostics, including regime identification and wall flow structure recognition, two methods for electrochemical signal processing are investigated and compared within an experimental network of crossing minichannels. One method is based on the use of a transfer function, while the other, the so-called Sobolik solution (Sobolik et al. in Coll Czech Chem Commun 52:913-928, 1987), consists of finding a direct solution to the mass balance equation. Sobolik's method has been selected given its ability to provide a description, over a wide range of Reynolds numbers (317 \ Re \ 3,535), for all wall shear rate fluctuations, as well as for the associated mixing scales in the power spectra density (PSD). This technique is then applied to flow within micromixers composed of two crossing microchannels in order to study highly unsteady and inhomogeneous microflows. The hydraulic diameters of the studied channels are 500 and 833 lm, respectively. Two flow patterns are investigated herein: the crossing-flow type and the impinging flow (or so called co-flow) for a Reynolds number range between 173 and 3,356. The PSD of wall shear rate fluctuations reveals various flow characteristics depending on the microchannel aspect ratio.

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“…Determining the transfer function has been the objective of several studies (Deslouis et al 1990;Nakoryakov et al 1986). This function allows identifying wall shear stress dynamics.…”

Section: Electrodiffusion Technique For Wall Shear Rate Determinationmentioning

confidence: 99%

Unsteady flows in milli- and microsystems: analysis of wall shear rate fluctuations

Huchet¹,

Legentilhomme

Legrand

et al. 2011

Exp Fluids

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“…Through Faraday's law, Equation (1), the current fluctuations are directly proportional to the mass flux fluctuations. The mass flux on the wall is proportional to the concentration gradient, so statistical analysis of current fluctuations allows us to obtain important information concerning the turbulent transfer characteristics within the viscous sublayer [1,10,11,[18][19][20][21][22][23]. The detailed study of the near wall turbulent transfer is possible by using a matrix of measuring electrodes [19].…”

Section: Spectral Analysis Of Mass Flux and Wall Shear Stress Fluctuamentioning

confidence: 99%

“…For the smooth ('ideal') electrode the transfer function H(f) was calculated analytically and numerically [1,18,20]. Thereafter, for the normalising form of the transfer function "…”

Section: Spectral Analysis Of Mass Flux and Wall Shear Stress Fluctuamentioning

confidence: 99%

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On the electrochemical flow measurements using carbon-based screen-printed electrodiffusion probes

et al. 2005

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In this article, we have studied the possibility of using carbon-based screen-printed probes for electrochemical flow and mass flux measurements. Such probes have, up to now, been mainly used as biosensors to study in vivo reactions. Our study shows that screen-printed sensors allow the measurement of mass flux and mean wall shear stress with good accuracy and high reproducibility. The existence of a micro-porous layer covering the surface of screen-printed electrodes has been revealed by means of the impedance measurements and has been confirmed by Scanning Electron Microscopy. This layer influences the statistical characteristics of the turbulent limiting diffusion current and should be taken into account as an additional transfer function between the current and the velocity fluctuations. The use of screen-printed sensors opens new possibilities in the field of electrochemical flow diagnostics. The advantage of this new manufacturing technology lies in the possibility of serial mass production at very competitive prices (disposable sensors) combined with the possibility of the manufacture of segmented electrodes or matrix of electrodes. These new possibilities can be used for various industrial applications as well as for scientific studies on near-wall turbulent mass transfer. Furthermore, it is possible to envisage the development of a hybrid sensor (electrodiffusional/biochemical) allowing the study of in situ biochemical reactions in a flow

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“…The electrochemical (electrodiffusion) diagnostics of flows are widely used for the measurements of the wall velocity gradient and the local wall shear stress s w in electrolyte solutions [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. This method is based on the measurement of the limiting diffusion current I on small flush-mounted electrodes.…”

mentioning

confidence: 99%

Electrodiffusion diagnostics of laminar flows using the delay-time method

2007

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Electrodiffusion diagnostics are widely used for measurement of local wall shear stresses in liquid flows. At present, this method requires special electrolytes, so the applications are limited to laboratory conditions. Another problem concerns the dependence of the limiting diffusion current on the electrode surface state and on the bulk concentration of the electroactive species. In this paper, it is shown that the delay time between generation of the electroactive species and their detection on the downstream electrode, is directly related to the local wall shear stress value. Thus, the measurements of the delay-time open a new way for the study of near-wall hydrodynamics. This new method has been confirmed experimentally using an electrolyte containing the conventional hexacyanoferrate(III/II) redox couple, as well as with the chlorine (chloric(I))/ chloride couple in an electrolyte similar to seawater.

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Frequency response of electrochemical sensors to hydrodynamic fluctuations

Cited by 87 publications

References 20 publications

Unsteady flows in milli- and microsystems: analysis of wall shear rate fluctuations

Unsteady flows in milli- and microsystems: analysis of wall shear rate fluctuations

On the electrochemical flow measurements using carbon-based screen-printed electrodiffusion probes

Electrodiffusion diagnostics of laminar flows using the delay-time method

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