Euler force-assisted sequential liquid release on the centrifugal microfluidic platform

Abstract

The sequential release of liquid is essential for the automation of multistage biochemical analyses, such as immunoassays and nucleic acid extraction. Current methods for sequential liquid release are either too complicated owing to the bulky external control component or lack of flexibility. The Euler force can be flexibly adjusted on centrifugal platforms; this characteristic has great potential for developing interior force-triggered valves, increasing the methods for liquid manipulation in centrifugal microfluidic devices. In this study, a Euler force-assisted method is proposed to realize sequential liquid release in a convenient and flexible manner. The Euler force-assisted siphon valve proposed in this study has an ascent part of the siphon channel for priming by Euler force and a descent part for priming by capillary forces so that this siphon can be actively actuated by acceleration. With a certain channel size and angle, siphons with different lengths of the ascent channel can be triggered by different Euler forces, making the controllable release of liquid with different accelerations possible. By the simple combination of this kind of siphon, multiple unit operations can be realized, including sequential release, selective distribution, interruptible priming, and multistep immunoassay. This suggests that Euler force-assisted siphon priming can be a simple but efficient solution for complex liquid manipulation on the centrifugal microfluidic platform.