All inkjet-printed piezoelectric polymer actuators: Characterization and applications for micropumps in lab-on-a-chip systems

Abstract

Digital printing technologies are promising as future manufacturing approaches due to their capabilities of highly flexible and additive material deposition on various substrates. In this contribution, all inkjet-printed piezoelectric polymer actuators are presented based on polyvinylidene fluoride trifluoroethylene (P(VDF-TrFE)) and electrodes printed from silver nanoparticle dispersions. The target application for the actuators described here are membrane pumps for microfluidic lab-on-a-chip (LOC) systems. For the first time, all-inkjet-printed P(VDF-TrFE) actuators are reported and the corresponding piezoelectric d31 coefficient is measured. For manufacturing the actuators, a low-cost procedure is employed that consists of only three inkjet printing and post-processing steps where moderate thermal treatments (Tmax=130°C) are combined with plasma sintering. The processing is therefore compatible with a wide range of temperature sensitive polymer substrates, completely additive and highly flexible. A sandwich-like structure of a piezoelectric P(VDF-TrFE) layer between two silver electrodes is inkjet-printed onto a polyethylene terephthalate (PET) substrate. When a voltage is applied across the piezoelectric layer, the reverse piezoelectric effect will lead to a bending deflection of this unimorph structure. The piezoelectric d31 coefficients are found to be approximately 7 to 9pmV−1, which allows the generation of significant actuator deflections. For the application in a micropump, flow rates of several 100μLmin−1 are anticipated, which is promising for LOC applications. Most current micropumps are based on actuator elements that are fabricated separately and mounted on a passive membrane. By using all inkjet-printed actuators, as presented here, the joining step is avoided and the benefits of low-cost printed devices are added to the well-developed processing approaches for microfluidic chips.