Active and passive microfluidic valves, thermopneumatic pumps and low-power dosing systems have been fabricated using a new family of fabrication processes. These new processes are capable of producing integrated planar microfluidic systems with a one-thousand-fold increase in flow control over existing planar systems. The three fabrication processes described in this dissertation are capable of producing microfluidic valves with fluidic resistances on the order of 1015 Ns/m^5 and fluidic-resistance ratios greater than 4,000 for deionized water. Each of the three processes is tailored for a specific application but all can simultaneously produce integratable valves, fluidic channels, mixing chambers, thermoelectric heaters, and electrolysis electrodes. This large array of possible fluidic components makes it now possible to fabricate useful planar microfluidic systems.
The active valves controlled flow sufficiently for dosing insulin into an adult human andrequire as little as 9 μJ to operate. The passive valves demonstrated more than a ten-fold increase in sealing over previous planar one-way valves. The active and the passive valves have been implemented in low-power dosing systems and thermopneumatic micropumps, respectively. Both systems represent increases in performance relative totheir existing planar counterparts. The dosing system was designed to store fluid at an elevated pressure and dispense it on command, essentially making it a pump that requires power only to operate the bistable valve to function. The thermopneumatic pump can pump up to 9 μL/min and 16 kPa, representing 24% larger flow rates and up to 59% greater pressures for a given power consumption than existing planar pumps because of the improved sealing of two passive one-way valves used in the mechanical pump design.
Also described is the assembly method for microfluidic components that encapsulates the system with both fluidic headers and electrical interconnects. Prior academic packaging and sealing efforts produced chips with physically large fluidic interconnects assembled in serial fabrication steps and could not provide electrical connection to the fluid. The new method creates zero-dead volume fluidic interconnects to the chip and packages it in a standard DIP geometry for simple electronic integration with commercial solid-state devices.
December 31, 2004
Frank, J. A. (2004). Planar Microfluidic Devices for Control of Pressure-driven Flow. United States: University of California, Berkeley.