Precise evaluation of liquid conductivity using a multi-channel microfluidic chip and direct-current resistance measurements

Noh, Hyowoong; Lee, Junyeong; Lee, Chang-Ju; Jung, Jaedong; Kang, Jaewoon; Choi, Muhan; Baek, Moon‐Chang; Shim, Jae Hoon; Park, Hongsik

doi:10.1016/j.snb.2019.126810

Cited by 8 publications

(10 citation statements)

References 42 publications

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“…Here, 2 R int is the electrode–electrolyte interface resistances of the two wires due to their electric double layers in series with the nonuniform solution resistances near the wires. 29 R sol. is the bulk solution resistance which is relatively high for the cases in this study with samples containing low salt concentrations, i.e., high resistivities.…”

Section: Materials and Methodsmentioning

confidence: 99%

Low-Cost Resistive Microfluidic Salinity Sensor for High-Precision Detection of Drinking Water Salt Levels

2022

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Rapid, inexpensive, and precise water salinity testing remains indispensable in water quality monitoring applications. Despite many sensors and commercialized devices to monitor seawater salinity, salt detection and quantification at very low levels of drinking water (below 120 ppm) have been overlooked. In this paper, we report on optimization of a low-cost microfluidic sensor to measure water salinity in the range of 1–120 ppm. The proposed design employs two copper microbridge wires suspended orthogonally in a PDMS microchannel to measure salinity based on the electrical resistance between the wires. The preliminary design of the sensor microchannel with a rectangular cross-section width ( w ) of 900 μm and height ( h ) of 500 μm could measure the water salinity in the range of 1–20 ppm in less than 1 min with detection sensitivity, limit of detection (LOD), and limit of quantification (LOQ) of 17.1 ohm/ohm·cm , 0.31 ppm, and 0.37 ppm, respectively. Data from the preliminary design was used for developing and validating a numerical model which was subsequently used for parametric studies and optimization to improve the sensor’s performance. The optimized design demonstrated an order of magnitude increase in sensitivity (385 ohm/ohm·cm), a 6-fold wider detection range (1–120 ppm), and a 15-fold enhancement in miniaturization of the microfluidic channel ( w = 200 μm and h = 150 μm) with LOD and LOQ of 0.39 and 0.44 ppm, respectively. In the future, the sensor can be integrated into a hand-held device to remove present impediments for low-cost and ubiquitous salinity surveillance of drinking water.

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Section: Materials and Methodsmentioning

confidence: 99%

Low-Cost Resistive Microfluidic Salinity Sensor for High-Precision Detection of Drinking Water Salt Levels

2022

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“…Applying the sin wave voltage with 1 kHz frequency between electrodes inside the water sample is a suitable condition for water EC measurement [28]. The merit of using the frequency method against the capacitive method is that in the capacitive method, the value of the capacitor and water sample conductivity varies by environmental variations, especially by temperature, which results in noticeable measurement errors.…”

Section: Ec Measurementmentioning

confidence: 99%

“…At the first step for TDS measurement and voltage offset purpose, the ICL7660 gets the 3 V voltage from the regulator and converts it to −3 V. Finally, the −0.5 V is obtained after passing by R 1 and R 2 resistance. The −0.5 V offset voltage is given to the AC voltage to eliminate the DC value, since, DC value can decompose water molecules [28,34]. Then, the voltage is applied to an electrode of the strip which causes the current to pass through the sample water molecules and reaches the other electrode.…”

Section: Ec Measurementmentioning

confidence: 99%

“…Depending on the device design, the electrodes-based method includes two, three, or four electrodes. The electrode-based method is also divided into capacitive and frequency methods [27,28]. Meanwhile, one of the most common challenges in electrode-based TDS sensors is the corrosion of electrodes which results in measurement errors and requires further calibration [26,29].…”

Section: Introductionmentioning

confidence: 99%

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A strip‐based total dissolved solids sensor for water quality analysis

Akram

Ramezannezhad

Nikfarjam

et al. 2022

IET Science Measure & Tech

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In this study, a portable Total Dissolved Solids (TDS) and Electrical Conductivity (EC) of water sensor using a disposable polymer strip and the readout circuit segments is presented. The strip consists of gold electrodes and a vent hole for water flow injection inside the measurement chamber. This strip reduces the cost of the measurement, decreases the measurement duration, and increases the repeatability of the system. Besides, there is no demand for electrodes cleaning and recalibration of the system. According to the electrical model of strip electrodes and their frequency responses, the EC value is in the range of 78.1-1230.8 (µs)/cm. The experimental tests are carried out based on the frequency method in the concentration range within 50-800 ppm. The results confirm the linear relation of TDS concentration on the EC voltage value which is 1.9 mV for 1 ppm resolution. Also, the effect of temperature variations on the EC value is investigated. Furthermore, the average amount of error for EC measurement exhibits an acceptable amount in comparison with other studies. Moreover, studying the drift variations for 20 days reveals the maximum drift of 1.6%. Finally, according to the present study, the sensor is a suitable candidate for practical applications.

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“…For salinity measurement, the conductivity meters [9,10] are the most widely used and two electrodes are exploited to detect the water conductivity, related to the concentrations of the dissolved salt. However, this method can easily cause water polarization [11]. Besides, when the electrodes are covered by a dirty substance, the length and area of the electrodes will change.…”

Section: Introductionmentioning

confidence: 99%

Water Temperature and Salinity Measurement Using Frequency Comb

Zhang

Zhao

et al. 2019

Applied Sciences

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Water temperature and salinity are key parameters in many fields such as industry, forestry and agriculture. In this paper, we, theoretically and experimentally, demonstrate a method which is capable of water temperature and salinity measurement based on a laser frequency comb at 518 nm. We have developed a simple Michelson interferometer system. By scanning a mirror on a precision displacement platform, a pair of cross-correlation patterns can be obtained. The real-time optical distance information from these cross-correlation patterns can be used to calculate the optical distance difference changes. Temperature and salinity can be measured via these changes, aided by the empirical formulas. Compared with the reference values, our results show the differences of below 0.12 °C for temperature measurements, and 0.06 ‰ for salinity measurements. The obtained results indicate that our method can offer a powerful scheme for future temperature and salinity measurement.

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Precise evaluation of liquid conductivity using a multi-channel microfluidic chip and direct-current resistance measurements

Cited by 8 publications

References 42 publications

Low-Cost Resistive Microfluidic Salinity Sensor for High-Precision Detection of Drinking Water Salt Levels

Low-Cost Resistive Microfluidic Salinity Sensor for High-Precision Detection of Drinking Water Salt Levels

A strip‐based total dissolved solids sensor for water quality analysis

Water Temperature and Salinity Measurement Using Frequency Comb

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