(258a) Pneumatically Controlled 32 Channel Scalable Disposable Microfluidic Sample Handling Device with Integrated Metering, Mixing, and Demultiplexing

As the popularity of integrated LOC systems grows the need for sterilization tolerant or disposable components will follow. Many LOC systems must be carefully sterilized and regenerated. These procedures can often be costly, time consuming, and in some cases require manual intervention. Also, the additional resources required to implement such procedures, i.e. pumps, valves, solution storage, etc., can be undesirable. They can also contribute to the possibility of inaccurate results if not carried out properly. Additionally the device material may have a limited number of sterilization cycles before its efficacy is compromised. Geometry can also contribute to the difficulty associated with sterilization. In many LOC systems this challenge is addressed by simply disposing of the entire device after a single test thus eliminating any possibility of cross-contamination. While the method is scientifically effective many times it is not cost effective. This paper presents the design, fabrication, and testing of a device capable of multiple disposable tests on a single soft lithography fabricated device. The device combines the cost effectiveness of sterilization and reuse of large-area resources as well as the additional robustness of disposable small-area components. The device is constructed exclusively of polydimethylsiloxane or PDMS. Portions of the device were cast using soft lithography and xurography while other components, such as membranes, were created by spinning uncured PDMS onto polystyrene substrates. The construction is a sandwich type. The device consists of six functionally important layers. The first two layers implement the metering system in which volumetrically identical samples can be created. This subcomponent is reusable and serves as the first step before samples are directed to one of the 32 pathways. The third and fourth layers implement the demultiplexing of the sample as well as a separate demultiplexing of an additional reagent. The fifth and final layers implement the disposable reaction chambers and route the sample to an interface for use in further manipulation. The mux assemblies function identically. The control lines actuate both devices simultaneously. The addressing scheme implemented for pathway selection in the system is a based on a simple binary solution commonly used in electronic multiplexors. The pneumatic solution however, requires twice the number of control lines. This is due to the number of valves necessary to simply implement the demux/mux and the single pole single throw nature of the pneumatic valve. The relationship is as follows; where n is equal to the number of valves and f is equal to the number of filters f=2^(n/2). This relationship becomes exponentially beneficial as the number of individual filters is increased. Note that n must be an even nonzero value. This system has shown to integrate both disposable and reusable components and utilize the unique benefits of each. The system has also been designed such that additional reusable and disposable components can be added in series or parallel by re-implementing one of the already existing layers.