Abstract
Microfluidic systems are of paramount importance in various fields such as medicine, biology, and pharmacy. Despite the plethora of methods, accurate dosing and mixing of small doses of liquid reagents remain challenges for microfluidics. In this paper, we present a microfluidic device that uses two micro pumps and an alternating drive pattern to fill a microchannel. With a capacitive sensor system, we monitored the fluid process and controlled the micro pumps. In a first experiment, the system was set up to generate a 1:1 mixture between two fluids while using a range of fluid packet sizes from 0.25 to 2 µL and pumping frequencies from 50 to 100 Hz. In this parameter range, a dosing accuracy of 50.3 ± 0.9% was reached, validated by a gravimetric measurement. Other biased mixing ratios were tested as well and showed a deviation of 0.3 ± 0.3% from the targeted mixing ratio. In a second experiment, Trypan blue was used to study the mixing behavior of the system. Within one to two dosed packet sets, the two reagents were reliably mixed. The results are encouraging for future use of micro pumps and capacitive sensing in demanding microfluidic applications.
Highlights
Microfluidic devices are becoming more and more common in a variety of fields, including point-of-care diagnostics, pharmaceutical research, and biology [1]
A key challenge for every microfluidic device is the control of the fluid flow inside the system
Many microfluidic systems use closed-loop systems based on flow sensors, which are based on mechanical cantilevers [8,9,10], thermal anemometers [11,12], or Coriolis force measurement [13,14]
Summary
Microfluidic devices are becoming more and more common in a variety of fields, including point-of-care diagnostics, pharmaceutical research, and biology [1]. Many microfluidic systems use closed-loop systems based on flow sensors, which are based on mechanical cantilevers [8,9,10], thermal anemometers [11,12], or Coriolis force measurement [13,14]. Another commonly used method is capacitive fluid sensing. The sensor system described in [19] uses the capacitance change induced by air bubbles injected into a fluid stream for continuous flow measurement. Another example for non-continuous flow is the dosing system developed by Zhang et al [20], which uses a capacitive sensor electrode to measure the fluid amount dosed into a channel cavity
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