Microfluidic active pressure and flow stabiliser

Abstract

In microfluidics, a well-known challenge is to obtain reproducible results, often constrained by unstable pressures or flow rates. Today, there are existing stabilisers made for low-pressure microfluidics or high-pressure macrofluidics, often consisting of passive membranes, which cannot stabilise long-term fluctuations. In this work, a novel stabilisation method that is able to handle high pressures in microfluidics is presented. It is based on upstream flow capacitance and thermal control of the fluid’s viscosity through a PID controlled restrictor-chip. The stabiliser consists of a high-pressure-resistant microfluidic glass chip with integrated thin films, used for resistive heating. Thereby, the stabiliser has no moving parts. The quality of the stabilisation was evaluated with an ISCO pump, an HPLC pump, and a Harvard pump. The stability was greatly improved for all three pumps, with the ISCO reaching the highest relative precision of 0.035% and the best accuracy of 8.0 ppm. Poor accuracy of a pump was compensated for in the control algorithm, as it otherwise reduced the capacity to stabilise longer times. As the dead volume of the stabiliser was only 16 nL, it can be integrated into micro-total-analysis- or other lab-on-a-chip-systems. By this work, a new approach to improve the control of microfluidic systems has been achieved.

A low-cost microfluidic flow stabilizer for enhancing QCM measurement stability in in-liquid bio-applications

“…Previous studies have explored different methods to address flow rectification in microfluidic systems. Different active flow stabilizers were proposed [12,13]. However, the need for external components and power sources increases the complicity and costs of these systems.…”

Method to fabricate round cross‐sectional channel using thermal expansion of air for passive flow regulators

“…Microfluidic pressure and flow regulators are divided into active and passive regulators. Active methods enable precise flow manipulation but require external devices and complex systems [7][8][9][10]. In contrast, using passive regulators is a convenient and alternative method for effective flow control.…”

An integrated resource-efficient microfluidic device for parallelised studies of immobilised chiral catalysts in continuous flow via miniaturized LC/MS-analysis

“…35–38 By immobilizing the respectively investigated catalysts on a solid support, a simplified separation of the catalyst and reaction products is furthermore possible. 39–42 Especially, in combination with integrated on-line analytics, 43–47 and due to the comprehensive flow control in lab-on-a-chip-devices, 48–50 integrated microreactors can offer a fast and efficient option for screening experiments. 51…”

“…[35][36][37][38] By immobilizing the respectively investigated catalysts on a solid support, a simplified separation of the catalyst and reaction products is furthermore possible. [39][40][41][42] Especially, in combination with integrated on-line analytics, [43][44][45][46][47] and due to the comprehensive flow control in lab-on-a-chip-devices, [48][49][50] integrated microreactors can offer a fast and efficient option for screening experiments. 51 Previously, we reported on two microfluidic systems, combining a packed microreactor either in a micro batch-like manner (stopped-flow), 52 or in continuous flow to an embedded chiral separation unit with subsequent MShyphenation by using only a minimized amount of catalytic material.…”