Pneumatic siphon valving and switching in centrifugal microfluidics controlled by rotational frequency or rotational acceleration

Air-pressure-mediated, pneumatic siphon valves employ temporary storage and subsequent release of pneumatic energy, exclusively controlled by rotation of the disk. Implementation is easy, and robust valves can be integrated in a monolithic way at minimum additional costs. However, so far, pneumatic siphon valving requires deceleration from high to low rotational frequencies. Valve opening is performed always when the rotation of the disk drops below a critical rotational frequency. To overcome this limitation, we introduce new concepts for pneumatic siphon valving which enable operation of the disk at any rotational frequency without unwanted bursts of the siphon valves. Thus, the design space for pneumatic siphon valves in centrifugal microfluidics is significantly extended. Three types of pneumatic siphon valves are presented with release control at (1) rotational frequencies between 25 and 48 Hz, (2) positive rotational accelerations between 1 and 22 Hz s−1, and (3) negative rotational accelerations between 5 and 20 Hz s−1. Finally, we combine two valve types to realize robust switching into two fluidic paths with flow rate ratios of 94/6 and 0/100.