Rapid prototyping of pneumatically actuated hydrocarbon gel valves for centrifugal microfluidic devices.

A novel, easy to prototype hydrocarbon gel-based active valve was developed for use in centrifugal microfluidic devices. The valve has been demonstrated to restrict flow by an additional 1000 revolutions per minute (RPM) when compared to a passive capillary valve of the same size located at the same radius. Opening of the valve is accomplished in a contactless manner using a stream of focused compressed air. The ease of fabrication, low cost and small dimensions of the gel valve offer the potential for integration of multiple valves of this type into multi-process centrifugal microfluidic systems.

Automated liquid-liquid extraction by pneumatic recirculation on a centrifugal microfluidic platform.

In this technical note, a liquid-liquid extraction technique was performed using pneumatic liquid recirculation on a centrifugal microfluidic device. Non-contact pneumatic pumping enabled a multi-cycle liquid-liquid extraction process using aqueous iodine in a potassium iodide solution and hexadecane while requiring a minimal amount of space on the device. The extraction process was completely automated on the device following sample introduction and required only 50 s for each extraction cycle. The pumping rate achieved during liquid recirculation was 120 ± 10 µL/min. A recycling process such as the one demonstrated would be difficult to implement in a conventional centrifugal microfluidic system.

Rapid simultaneous determination of nitrate and nitrite on a centrifugal microfluidic device.

A centrifugal microfluidic device was developed for the rapid sequential determination of two critical environmental species, nitrate and nitrite, in water samples. The nitrate is reduced to nitrite and the nitrite is derivatized. The analytes are determined spectrophotometrically through the disc with a 1.4mm pathlength. The detection limits are 0.05 and 0.16 mg L(-1) for nitrite and nitrate respectively. The use of powdered reagents, the 100 microL sample required and the design of the device suggest that it would be suitable for field use.

A rapid prototyping technique for valves and filters in centrifugal microfluidic devices.

Using short lengths of fused silica capillary tubing embedded in the disk, a system for valving and filtering samples on centrifugal microfluidic devices has been designed and implemented. Sedimentation of turbid samples and transfer of the clear supernatant was also accomplished. Also demonstrated is the transfer of the liquid through a second capillary valve to the final reservoir. By controlling rotational speed, sedimentation and multiple step valving operations are readily implemented and easily prototyped.