Free Suspended Thin-Walled Nickel Electroplated Tubes for Microfluidic Density and Mass Flow Sensors

Abstract

In this paper, a novel fabrication method is proposed for microfluidic tubes with a large diameter, circular cross-section, and thin wall. These properties make the tubes especially suitable for density sensors and Coriolis mass flow sensors, because of the resulting low tube mass, low-pressure drop, and low pressure-dependence of the tube shape. A demonstrator sensor was fabricated and the first measurement results of fluid density and mass flow are presented. The low-cost fabrication method is based on electroplating technology and results in tubes with a near-perfect circular cross-section. Diameters ranging from 120 µm to 1 mm and wall thicknesses from 8 µm to 60 µm have been achieved. For the demonstrator sensor presented in this paper a freely suspended tube was realized with a total length of 37 mm, a diameter of 600 µm, and a wall thickness of 20 µm. Density measurements were performed using various gases, liquids, and liquid mixtures at 21 • C to 23 • C lab temperature. The accuracy of the measured densities of gases such as nitrogen, argon, and helium is 5%. For liquids including DI water, isopropyl alcohol (IPA), and their various mixtures an accuracy of 0.5% was obtained. Preliminary mass flow rate measurements were performed with water and isopropyl alcohol up to 30 g/h with less than 30 mbar pressure drop thanks to the large tube diameter.[2021-0179]

Modeling, Fabrication, and Testing of a 3D-Printed Coriolis Mass Flow Sensor

“…As is clear from Figure 11, the measured pressure drop is significantly higher because of the extra pressure drop in the relatively long connecting tubing between the sensor and the two pressure sensors. pressure drop for water and IPA should be 1.1 mbar and 0.8 mbar, respectively [17]. The pressure drop for nitrogen is expected to be around 5 mbar, mainly due to the two 90degree bends in the tube.…”

“…The pressure drop over the tube vs. flow rate is shown in Figure 11. An estimation of the pressure drop based on the Hagen-Poiseuille equation shows that the maximum pressure drop for water and IPA should be 1.1 mbar and 0.8 mbar, respectively [17]. The pressure drop for nitrogen is expected to be around 5 mbar, mainly due to the two 90-degree bends in the tube.…”

“…However, these technologies resulted in a rectangular cross-sectional tube shape. To obtain a circular cross-sectional shape, electroplated nickel [17] tubes and glass capillaries [18] can be considered. In [17], it was shown that the nickel-plated tubes can in principle be used in a Coriolis mass flow sensor, but the demonstrated performance needs much improvement.…”

“…To obtain a circular cross-sectional shape, electroplated nickel [17] tubes and glass capillaries [18] can be considered. In [17], it was shown that the nickel-plated tubes can in principle be used in a Coriolis mass flow sensor, but the demonstrated performance needs much improvement. Glass capillaries have been used successfully for density and mass sensing.…”

Compact Micro-Coriolis Mass-Flow Meter with Optical Readout

“…As will be shown in Section 2 , to obtain a high sensitivity for fluid density and mass flow, the mass of the channel should be small compared to the mass of the fluid. Therefore, the inner diameter or cross-sectional area of the channel should be large compared to the wall thickness [ 16 ], or a low-density wall material should be chosen. A large channel diameter also has the advantage that it results in a low pressure drop over the sensor.…”