Abstract
A microfluidic chip with a controllable and integrated piezoelectric pump was proposed and demonstrated, where the pump was designed as a micro-actuator based on polyvinylidene fluoride (PVDF) organic piezoelectric film. In this case, the pump should integrate with the microfluidics device very well into one chip. The flow rate can be precisely controlled in the range of 0–300 µl/min for water by tuning the Vpp and frequency of Alternating Current (AC) voltage applied on the diaphragm. To analyze the relationship between the flow rate and the deflection of diaphragm, the deformations of diaphragm at different voltages were researched. The displacement of diaphragm was defined as 17.2 µm at the voltages of 3.5 kV, 5 Hz when the pump chamber was full of water. We have used the integrated microfluidic chip with two pumps for droplet generation to demonstrate its great potential for application in droplet-based microfluidic chip.
Highlights
IntroductionEven though capillary pump offers the advantages of low cost, contiguous flow and easy to integrating several pumps into one chip, but it has limitations in processing large volume of fluid and modulating flow rate due to complex pump geometrical design and physicochemical modification[28]
To address these issues, several self-powered or bulky facility-free pumps have been developed, such as finger or hand powered pump[23,24,25] and capillary pump[26]
In order to achieve precise controlled of flow in integrated microfluidic devices, many electronic materials have been used to fabricate pump, such as piezoelectric ceramics with big displacement and applied force[27, 31], piezoelectric films integrated with silicon membrane using Micro-Electromechanical Systems (MEMS) technology[32, 33], dielectric elastomeric with electrostriction for its flexibility and environmental performance[34]
Summary
Even though capillary pump offers the advantages of low cost, contiguous flow and easy to integrating several pumps into one chip, but it has limitations in processing large volume of fluid and modulating flow rate due to complex pump geometrical design and physicochemical modification[28]. Piezoelectric ceramics are fragile, while dielectric elastomeric is not stable when using for a long time and the process of MEMS is complex To address these issues, electrostrictive poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) thick film with a large electrostrictive strain has been used for pump, which can achieve maximum flow rate of around 25 μl/min for methanol at 63 Hz with a backpressure of 350 Pa35. We have integrated two PVDF piezoelectric pumps into one T-junction[36, 39, 40] microfluidic chip to generate droplets, where controlled droplet size was achieved by tuning the peak to peak value of driving voltage
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