Two key components of any fluidic system are valves and pumps. These are the basic mechanisms for creating and controlling fluid flow. In lab-on-chip (LOC) applications, where analytic processes are carried out on a microchip, the need for pumps and valves remains, but new designs are required to fit within the constraints of available microfabrication processes. Unfortunately, current designs for microfabricated valves and pumps impose a significant chip-to-world burden, and this burden impedes progress towards greater miniaturization and integration of LOC systems.
Microfabrication processes, especially those suitable for mass production, are strongly biased towards planar geometries. This flattening of geometries makes traditional macroscopic designs unworkable or inefficient. This has affected the types of valves and pumps that are being used in LOC applications. For this reason many workers in the field have switched from mechanical pumps to other transduction mechanisms, such as electro-osmotic flow (EOF). However, these new mechanisms can have a number of significant drawbacks, such as affecting ion concentrations, which are significant when attempting to perform chemical reactions. For this reason, many groups have continued to use mechanical pumps. In particular, microfluidic “peristaltic” pumps have become very popular. Underlying the operation of peristaltic pumps, which are different in design from their macroscopic counterparts, is the operation of a sequence of active valves. In particular, existing processes actuate the valves and pumps using pneumatic control signals that are generated off-chip. This imposes significant interconnect burdens to the system design.
Even more critical is the fact that existing microfabrication processes support only limited system integration. Fluidic channels, valve, pumps, and aqueous contacts are commonly supported, but all other components are off-chip. A very small portion of the systems' overall complexity is embedded on the chip. This divide essentially creates a barrier to increased integration.