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.
Highlights
Pressure is one of the key factors in microfluidic systems, which has been intensively studied in various applications
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
Since the voltage change was completely saturated within 1 min at the given flow rate, each flow rate was maintained for 1 min to ensure full deflection of the PDMS thin membrane
Summary
Pressure is one of the key factors in microfluidic systems, which has been intensively studied in various applications. High-performance pressure sensors are required to achieve desired results in various applications; diverse pressure-sensor types have been widely reported, such as in optical or electrical measurement methods. In the case of the interface-monitoring-type, the experimental results are affected by the reference fluid, which directly contacts the sample fluid Electrical measurement types, such as capacitive [22,23,24] and resistive [25,26,27,28] pressure sensors, have been intensively investigated owing to their simple measurement methods compared with the optical type. Liquid metal-based pressure sensors can provide high stability for long-term experiments, simple measurement and fabrication methods, and can be integrated in various lab-on-a-chip systems. The proposed pressure sensor is highly reversible without showing damage, even at high pressure
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