Bionische Mikrofluidventile aus Polydimethylsiloxan nach dem Vorbild der Venenklappen
- Bionic polydimethylsiloxane - based microfluidic valves derived from the venous valve principle
Klammer, Ingo; Mokwa, Wilfried (Thesis advisor)
Aachen : Publikationsserver der RWTH Aachen University (2010, 2011)
Dissertation / PhD Thesis
Aachen, Techn. Hochsch., Diss., 2010
Microfluidic valves are the central elements within complex microfluidic networks to control the fluids. In the human blood stream venous valves representing flexible passive valves to control the blood flow. The venous current is generated passively against the force of gravity by using venous valves. When realized in flexible substrates such as e.g. Polydimethylsiloxane (PDMS) passive venous valves can operate without peripheral devices and the need of an oscillating flow in microfluidic devices. This thesis reports on an implementation of a novel microfluidic valve based on the venous valve principle of human blood system for complex pneumatically actuated microfluidic networks. Using PMDS as a substrate the microfluidic valves were designed derived by the biological archetype, analytically and numerical analyzed, fabricated and characterized. The valves were fabricated using standard softlithographic techniques and PMDS as a substrate. The venous valves with fluidic in- and output on one wafer and a polymeric membrane on a second wafer were structured in resist by standard lithographic techniques. The long-term influence of strong alkali solution (up to pH 13) like sodium hydroxide (NaOH) which is the most important pH suspending agent in biocatalytic reactions on the surface energy, the surface roughness and the absorption of the liquids has to the best of our knowledge not been reported adequately before. Therefore the change of PDMS interface characteristics due to the long-term influence of aqueous alkaline solutions was analyzed. Strong coupled field numerical simulations were used to analyze bionic, artificial micro-machined, PDMS-based venous microfluidic valves for the first time. The solution algorithm uses a fluid structural interaction (FSI) method for solving the interaction of the valve structure and the fluid field. Depending on different pressures the diodicities of the valves were simulated. To determine the diodicities of the venous-type valves and to verify the numerical simulations capacitive-based pressure sensors as well as fluorescence-based measurements were used. In comparison to conventional methods no external peripheral devices are necessary been connected to the fluidic system using the fluorescence-based measurements. The results indicate that the functional principle of bionic valves can be integrated in complex flexible, pneumatically actuated microfluidic systems to substitute active pneumatic valves and therefore significantly reduce the pneumatic periphery.
- Chair of Materials in Electrical Engineering I and Institute of Materials in Electrical Engineering