Authors: E.P. Furlani, K.C. Ng, A.G. Lopez, C. Anagnostopoulos
Affilation: Eastman Kodak, United States
Pages: 284 - 287
Keywords: jet instability, marangoni instability, continuous inkjet printing, microfluidic drop generator, thermal drop deflection, thermal microjet deflection
We present a novel CMOS/MEMS microfluidic device that enables the controlled production and redirection of streams of picoliter-sized droplets at frequency rates in the hundreds of kilohertz range. This device consists of a pressurized reservoir that feeds a micro-nozzle manifold with hundreds of active orifices, each of which produces a continuous jet of fluid. An integrated cylindrical blocking structure is suspended beneath each orifice. This structure splits the flow from the reservoir into two opposing flows that merge immediately beneath an orifice to form the jet. Each microjet is subjected to thermal modulation as it exits the orifice, which causes the formation of droplets downstream. Controlled thermal modulation is achieved using individually addressable resistive heater elements that are integrated into the nozzle plate around each orifice, and also into the suspended blocking structure. The heaters are configured to enable symmetric or asymmetric heating. Modulated symmetric heating produces a straight stream of droplets whereas asymmetric heating causes the stream to deflect. The ability to redirect droplets is useful for applications such as continuous inkjet printing in which only a fraction of the generated droplets are used to render an image; unused droplets are guttered and recirculated to the reservoir. The integrated CMOS-based thermal modulation and deflection capability of our device represents distinct advantages over conventional continuous inkjet printing systems that rely on piezoelectric driven drop generation and electrostatic deflection of charged droplets. In this presentation we discuss the fabrication and operating physics of our novel continuous microdrop generator. We present experimental data of droplet generation and deflection and compare this data with 3D CFD simulations. We also discuss applications of this device to continuous inkjet printing.