Learn about suspension compatible micro throttle pumps developed at the University of Hertfordshire.
Precisely controlled transport of fluids within microfluidic systems is crucial if microfluidic instruments are to be reliably employed.
Large numbers of microvalves and micropumps have been reported in the literature. However pumping of 'real-world' fluids (for instance biological cell suspensions) remains problematic.
We have developed piezoelectrically actuated PDMS-glass and PDMS-PMMA valves and pumps which minimize the problems of blockage and sticking often encountered with microvalves when applied in real-world applications.
Micro throttles utilise the elastic properties of polydimethylesiloxane (PDMS) elastomer substrates. Soft lithographic techniques are used to fabricate PDMS microstructures. Glass or PMMA diaphragms are used to seal the structure and are deflected by a piezoelectric bimorph actuator bonded to the top surface of the diaphragm. Actuation provides either a significant increase or decrease in the flow resistance of the PDMS throttles via displacement amplification within the PDMS microstructures.
Single piezo actuated Micro Throttle Pumps (MTPs) exploit elastic substrate regions which concurrently flex in opposing directions due to stresses induced in the composite substrate/diaphragm by flexure of the PZT.
We believe that MTPs have significant potential in areas requiring non-destructive transport of both particulate and cellular suspensions. In addition the simple planar fabrication technique presented represents a practical step towards implementation of low-cost integrated polymer based Microfluidic systems.
The latest generation of MTPs have been tested with water, suspensions of 5μm diameter polystyrene beads and whole (anticoagulated) blood. Maximum pumping rates of 2ml min-1 for water and 200μl min-1 for blood were achieved at frequencies up to 1500Hz and a maximum back pressure of 30 kPa was achieved with zero flow.
Unbonded MTPs have also been successfully shown to pump biological fluids and retain the ability to disassemble, clean and reuse extending the lifetime of pumping components working with real-world analytes.
The internal volume of the pump from input to output connection is just 1.4 microlitres.