| Thu November 12th 2009 16:00 HR Z203 | Seminar | 1. Stability and droplet formation in inkjet printing 2. Building water bridges in air (with the aid of some thousands of volts) Arjan van der Bos, Alvaro Marin |
Details:Droplets with a well-controlled and narrow size distribution are required in many industrial and medical applications, e.g. for inkjet printing or for the formation of medical inhaler microsprays. In this work we study droplet formation from a drop on demand inkjet print head using the Brandaris 128 ultra high-speed camera at 10 million frames per second as well as stroboscopic images of 6 nanoseconds. The results show that a long tail is formed after droplet formation. The detailed data reveal insight in the dynamics near the tail and the breakup phenomena. The onset of the Rayleigh Plateau instability and the scaling laws of the break up of the tail are studied with a numerical model based on the lubrication approximation. Excellent agreement was found between the numerical model and the experiments.A bubble can be entrained in the ink channel of a piezo-driven ink jet print head leading to malfunction. Here an acoustic sizing method for the volume and position of the bubble is presented. The influence of the bubble on the channel acoustics is detected by the piezo-actuator operating in a sensing mode. The acoustic response is also modeled in a linearized bubble dynamics model and we demonstrate how the size of the bubble and its position within the channel can be inferred from the inverse problem. The validity of the presented method is supported by time-resolved optical observations of the bubble dynamics visualized in a glass connection channel. The combined optical and acoustical recordings are compared to the model, where we find very good agreement. | ||
