Xurography actuated valving for centrifugal flow control

Abstract

We introduce a novel instrument controlled valving scheme for centrifugal platforms which is based upon xurography. In a first approach, which is akin to previously presented event-triggered flow control, the valves are composed of a pneumatic chamber sealed by a dissolvable film (DF) and by a pierceable membrane. Liquid is initially prevented from wetting the DF by the counter pressure of a trapped gas. Via a channel, this pocket is pneumatically connected to a vent, sealed by the pierceable membrane, located on the top surface of the disc. By scouring the top surface of the disc, along a pre-defined track by a robotic knife-cutter, the trapped gas is released and so the liquid can wet and disintegrate the DF. In order to automate assay protocols without the need to integrate DFs, we extend this xurography-based flow control concept by selective venting of chambers subjected to pneumatic over-pressure or vacuum suction. Unlike most instrument controlled flow-control mechanisms, in this approach to valve actuation can occur during disc rotation. To demonstrate the potential of this flow control approach, we designed a disc architecture to automate the liquid handling as the backbone of a biplex liver assay panel. We demonstrate valve actuation during rotation, using the robotic arm, using this disc with visualisation via dyed water. We then demonstrate the biplex liver assay, using calibration reagent, by stopping the disc and manually piercing the membrane to actuate the same valves.

Lab-on-a-CD: A Fully Integrated Molecular Diagnostic System

“…A hydrophobic membrane valve can be used in conjunction with dissolvable film to selectively flow aqueous and organic solutions into different chambers. [53][54][55][56][57] This technique has been used in combination with paper microfluidics to implement timed fluidic control 58 and has also been demonstrated in clinical applications, including a fluorescence-linked immunoassay and a liver assay panel.…”

Siphon-Induced Droplet Break-Off for Enhanced Mixing on a Centrifugal Platform

“…These lab-on-a-disc systems make specific use of the interplay of the frequency controlled centrifugal force and capillary action in a surface-functionalized network of micro-channels and cavities. Key liquid handling operations such as valving [44][45][46][47][48], metering [49,50], mixing [51,52], pumping [53][54][55], and switching/routing of flow [56,57] have been demonstrated.A major challenge for microfluidic systems is rapid mixing. In general, one can categorize micromixers according to different characteristics [58,59], e.g., batch and continuous flow mode, laminar and turbulent, planar and 3-dimensional geometry, low-or high-aspect-ratio structures, manufacturing technologies or active/passive mixers.…”

Wireless closed-loop control of centrifugo-pneumatic valving towards large-scale microfluidic process integration

“…By scouring the top of the disc with a robotic knife-blade, we could actuate valves during rotation [2]. Here, rather than piercing the membrane with a knifeblade, we use a gas-tight, low-melting temperature membrane (commonly available Parafilm) as our CF.…”

“…In this work, we combine the previously introduced 'electrified Lab-on-a-Disc' (eLoaD) [4] platform with our event-triggered dissolvable film (DF) valves [2] to actuate up to 128 valves in random sequence. In the conventional implementation, the event-triggered valves are composed of two dissolvable films, called the load film (LF) and control film (CF), placed in a dead-end pneumatic chamber.…”

“…This type of valve is typically based on unbalancing the hydrostatic equilibrium between rotationally induced pressure and the other forces acting on liquid elements such as pneumatic (counter) pressure or the capillary action; thus the key advantage is the only control input required is modulation of the spin rate. This category comprises capillary burst valves, siphons and dissolvable film barrier [2,3].…”