Fluidics-on-Flex circuits comprise circuit elements — fluid conductors, pumps capable of pumping against large back pressures, valves, reservoirs and reactors containing integral dry reagents. Some elements are fabricated in media with micrometer or nanometer scale flow channels or pores. The fluidic properties of an element are achieved by suitable design of: the element's shape, the dimensions of the flow channels or pores, the surface tension and zeta potential of element surfaces, and the location of flex electrode contacts and the power applied to them.
Fluidics-on-Flex circuits are initially dry, becoming fluidically active when fluids are introduced into the circuit at one or more locations. The fluids can include the sample fluid as well as other fluids contained in sealed reservoirs integral to the flex components. Fluids fill dry circuit elements either by capillary flow, pneumatically by the fluidic circuit's integral pumps or diffusively through a water vapor permeable wall. Fluidic elements, when combined into a Fluidics-on-Flex circuit, can perform complex fluidic manipulations.
There are two ways in which the Fluidics-on-Flex circuits have been fabricated: thin film and thick film format. The choice of format depends on the volume of fluid to be transported in the circuit and on the degree of integration or multiplexing.
For high sensitivity assays at low levels of multiplexing, thick film circuits are comprised of formed micro-porous elements laminated onto the electrode circuit of a flex circuit module. A typical fluidic element in this version of the technology contains microliter volumes of fluid capable of moving at flow rates of 0-100 nanoliters per second.
For high levels of multiplexing, thin film circuits are comprised of patterned micro-porous solvent-cast films deposited onto planar substrates with patterned electrodes. A typical fluidic element in this version of the technology contains nanoliter volumes of fluid capable of moving at flow rates of 0-100 picoliters per second.