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

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-ink-jet-printed P(VDF-TrFE) actuators are reported and the corresponding piezoelectric d(31) 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 (T-max = 130 degrees 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 d(31) coefficients are found to be approximately 7 to 9 pm V-1, which allows the generation of significant actuator deflections. For the application in a micropump, flow rates of several 100 mu L min(-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. (C) 2013 Elsevier B. V. All rights reserved.