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Highly stable liquid metal-based pressure sensor integrated with a microfluidic channel.

Jung T, Yang S - Sensors (Basel) (2015)

Bottom Line: Furthermore, the viscosity of various fluid samples was measured for a shear-rate range of 30-1000 s(-1).The results of Newtonian and non-Newtonian fluids were evaluated using a commercial viscometer and normalized difference was found to be less than 5.1% and 7.0%, respectively.The galinstan-based pressure sensor can be used in various microfluidic systems for long-term monitoring with high linearity, repeatability, and long-term stability.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical System Engineering, GIST, Gwangju 500-712, Korea. taekeonjung@gist.ac.kr.

ABSTRACT
Pressure measurement is considered one of the key parameters in microfluidic systems. It has been widely used in various fields, such as in biology and biomedical fields. The electrical measurement method is the most widely investigated; however, it is unsuitable for microfluidic systems because of a complicated fabrication process and difficult integration. Moreover, it is generally damaged by large deflection. This paper proposes a thin-film-based pressure sensor that is free from these limitations, using a liquid metal called galinstan. The proposed pressure sensor is easily integrated into a microfluidic system using soft lithography because galinstan exists in a liquid phase at room temperature. We investigated the characteristics of the proposed pressure sensor by calibrating for a pressure range from 0 to 230 kPa (R2 > 0.98) using deionized water. Furthermore, the viscosity of various fluid samples was measured for a shear-rate range of 30-1000 s(-1). The results of Newtonian and non-Newtonian fluids were evaluated using a commercial viscometer and normalized difference was found to be less than 5.1% and 7.0%, respectively. The galinstan-based pressure sensor can be used in various microfluidic systems for long-term monitoring with high linearity, repeatability, and long-term stability.

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Working principle of a galinstan-based pressure sensor. (a) When the membrane is subjected to pressure, the electrical resistance of the pressure sensor gets increased due to reduction in the cross-sectional area; (b) Schematic of the Wheatstone bridge circuit. The pressure is estimated by measuring the voltage difference between nodes A and B.
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sensors-15-11823-f002: Working principle of a galinstan-based pressure sensor. (a) When the membrane is subjected to pressure, the electrical resistance of the pressure sensor gets increased due to reduction in the cross-sectional area; (b) Schematic of the Wheatstone bridge circuit. The pressure is estimated by measuring the voltage difference between nodes A and B.

Mentions: Figure 2a shows a cross-sectional view of the proposed pressure sensor. Galinstan is introduced in the pressure-sensor channel, while the fluid flows through a fluidic channel located under the membrane. In this study, we utilized the electrical-resistance (Re) change of galinstan in the pressure sensor to measure the applied pressure. Electrical resistance is proportional to the resistivity and length of the pressure-sensor channel and inversely proportional to the cross-sectional area of the channel according to the electric-resistance theory form given by:(1)R e=ρ(l/A)where is the resistivity, is the length of the pressure sensor, and A is the cross-sectional area. The resistivity is constant as a physical property of galinstan, and the channel length is fixed for the employed device. Consequently, the electrical-resistance change is affected by the cross-sectional area change, which is also affected by pressure. At rest, the inlet (P1) and outlet (P2) pressures are identical, and the pressure sensor has an initial resistance because the membrane is not deflected. Meanwhile, the resistance of the pressure sensor increases because of the reduction in the channel area when P1 is higher than P2 under a certain flow rate. We can estimate the pressure at a specific position in the microfluidic channel by measuring the voltage signal, which is proportional to the resistance of the pressure sensor, using the data acquisition (DAQ) system of the LabVIEW program.


Highly stable liquid metal-based pressure sensor integrated with a microfluidic channel.

Jung T, Yang S - Sensors (Basel) (2015)

Working principle of a galinstan-based pressure sensor. (a) When the membrane is subjected to pressure, the electrical resistance of the pressure sensor gets increased due to reduction in the cross-sectional area; (b) Schematic of the Wheatstone bridge circuit. The pressure is estimated by measuring the voltage difference between nodes A and B.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4481972&req=5

sensors-15-11823-f002: Working principle of a galinstan-based pressure sensor. (a) When the membrane is subjected to pressure, the electrical resistance of the pressure sensor gets increased due to reduction in the cross-sectional area; (b) Schematic of the Wheatstone bridge circuit. The pressure is estimated by measuring the voltage difference between nodes A and B.
Mentions: Figure 2a shows a cross-sectional view of the proposed pressure sensor. Galinstan is introduced in the pressure-sensor channel, while the fluid flows through a fluidic channel located under the membrane. In this study, we utilized the electrical-resistance (Re) change of galinstan in the pressure sensor to measure the applied pressure. Electrical resistance is proportional to the resistivity and length of the pressure-sensor channel and inversely proportional to the cross-sectional area of the channel according to the electric-resistance theory form given by:(1)R e=ρ(l/A)where is the resistivity, is the length of the pressure sensor, and A is the cross-sectional area. The resistivity is constant as a physical property of galinstan, and the channel length is fixed for the employed device. Consequently, the electrical-resistance change is affected by the cross-sectional area change, which is also affected by pressure. At rest, the inlet (P1) and outlet (P2) pressures are identical, and the pressure sensor has an initial resistance because the membrane is not deflected. Meanwhile, the resistance of the pressure sensor increases because of the reduction in the channel area when P1 is higher than P2 under a certain flow rate. We can estimate the pressure at a specific position in the microfluidic channel by measuring the voltage signal, which is proportional to the resistance of the pressure sensor, using the data acquisition (DAQ) system of the LabVIEW program.

Bottom Line: Furthermore, the viscosity of various fluid samples was measured for a shear-rate range of 30-1000 s(-1).The results of Newtonian and non-Newtonian fluids were evaluated using a commercial viscometer and normalized difference was found to be less than 5.1% and 7.0%, respectively.The galinstan-based pressure sensor can be used in various microfluidic systems for long-term monitoring with high linearity, repeatability, and long-term stability.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical System Engineering, GIST, Gwangju 500-712, Korea. taekeonjung@gist.ac.kr.

ABSTRACT
Pressure measurement is considered one of the key parameters in microfluidic systems. It has been widely used in various fields, such as in biology and biomedical fields. The electrical measurement method is the most widely investigated; however, it is unsuitable for microfluidic systems because of a complicated fabrication process and difficult integration. Moreover, it is generally damaged by large deflection. This paper proposes a thin-film-based pressure sensor that is free from these limitations, using a liquid metal called galinstan. The proposed pressure sensor is easily integrated into a microfluidic system using soft lithography because galinstan exists in a liquid phase at room temperature. We investigated the characteristics of the proposed pressure sensor by calibrating for a pressure range from 0 to 230 kPa (R2 > 0.98) using deionized water. Furthermore, the viscosity of various fluid samples was measured for a shear-rate range of 30-1000 s(-1). The results of Newtonian and non-Newtonian fluids were evaluated using a commercial viscometer and normalized difference was found to be less than 5.1% and 7.0%, respectively. The galinstan-based pressure sensor can be used in various microfluidic systems for long-term monitoring with high linearity, repeatability, and long-term stability.

Show MeSH