Fluid Dynamics & Acoustics
How inkjet printing really works
Monday 13 - Tuesday 14 July, 2020
Online Course
COURSE FOCUS
Inkjet printing is a process of depositing on demand small droplets with a specified volume onto a precise location on a substrate. This definition covers a wide variety of applications like document printing, label printing, 3D printing, and functional applications like patterning of displays and biosensors. During the course we follow the ink all the way through the printhead, through droplet formation and on to landing on the substrate.
The course is mainly restricted to piezo-driven printheads jetting Newtonian inks, although the issue of viscoelastic inks will be discussed. A piezo-driven printhead is modelled as a set of acoustic cavities, the characteristics of which will be presented in the time (response to waveforms) and frequency domain.
The course is based on precise descriptions of the physical phenomena involved and on the derivation of the mathematical framework needed to solve the governing equations. Where possible the outcomes will be compared with experimental findings. Different mathematical methods will be presented to calculate the responses of different systems in the frequency and time domain. To describe correctly the behaviour of a printhead with a large number of narrow pitched nozzles, the long duct theory will be presented.
The aim of this course is to couple the characteristics of droplet formation and landing, spreading and permeation to the acoustics and microfluidics of the printhead. The knowledge conveyed during the course will enable the participants to analyse the behaviour of a wide variety of existing printheads and to support the development of new printheads and inks from a physics point of view.
COURSE OUTLINE (Central European Time)
Monday 13 July 2020
13:00 - 13:30 Log-on & join the meeting
13:30 Course begins
General introduction
Introduction on physics & mathematics
Basic concepts (single degree of freedom system)
Waveforms
Fluid dynamics
Mathematics
Different piezo designs
Helmholtz theory and waveforms (two and five degree of freedom systems)
Single nozzle printheads
Multi-nozzle devices
17:00 Session ends
Tuesday 14 July 2020
09:00 Session begins
Theoretical considerations
Long duct theory
Droplet formation
Speed of sound
Damping
Refilling
12:30 - 13:30 Break
13:30 Session begins
Further considerations
Maximum jetting frequency
Drag on droplets
Droplet impact and spreading
Jetting of viscoelastic inks
Examples: polyLED display printing, printing of biomolecules (co-authored by Dr Anke Pierik, Philips Research)
17:00 Course ends
Course Leader
Prof Dr J. Frits Dijksman
University of Twente, Faculty of Science and Technology, Netherlands
Prof Frits Dijksman is professor of biomedical applications of inkjet technology at the University of Twente, Netherlands. He has worked with Philips Research for more than 30 years and his main area of interest has been inkjet technology for consumer and non-consumer applications, such as PolyLED display manufacturing and the printing of biomolecules.