A flexible capacitance sensor integrated micropump for precise volume control



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Pneumatically actuated micropumps are operated by external pressure sources that enable deflection of the thin PDMS membrane. Depending on the geometrical parameters of the microvalve, these micropumps can deliver microliter to picoliter sample volumes precisely. However, the most conventional pneumatically actuated micropumps are operated by a fixed geometry under open-loop pressure control. Open-loop control limits the controllability of volume control per cycle and the reusability of the device In this study, we created an integrated system to improve the capability of pneumatically actuated micropumps. A parallel capacitive sensor based on a silver nanowire(AgNW)/poly(dimethylsiloxane) (PDMS) nanocomposite integrated into a micropump is developed to estimate the deflection of a thin PDMS membrane. The embedded flexible capacitance sensor shows excellent repeatability without altering the characteristics of PDMS membrane property. The output of this capacitive sensor was utilized for feedback signals passed to a PID controller, which integrated into the closed-loop system to manipulate the hydrodynamics force, flow speed, and volume per unit time with a wider range of volume control. The embedded flexible capacitance sensor showed great sensitivity and repeatability. With the advantages in adjustable pneumatic pressure and significant improvement in volume per cycle control resolution, this integration can be easily implemented into automatically controllable opening and closing pressure systems to rapidly control flow speed and transfer volume of contamination-free fluidic per unit time for full automation of microfluidic manipulation system.



Microvalve, Pneumatically actuated micropump, Silver nanowire, Flexible capacitance sensor, PID controller.