Inkjet Fluid Dynamics and Fundamentals - Part 2: Droplet Formation and Droplet Impact.
Instructor: J. Frits Dijksman, University of Twente
Level: Advanced/Specialist
Duration: 2:00 plus 15 minute break.  After the class, adjourn to Zoom to join the instructor and other students in a discussion of the class.
Course time: 
    New York: Monday 12 October 12:45 - 15:00
   London: Monday 12 October 17:45 - 20:00
   Tokyo: Tuesday 13 October 01:45 - 04:00

Benefits:
This course enables an attendee to:

• Learn about the design rules of piezo driven inkjet print heads.
• Discern the basics of formulation of ink in terms of viscosity (viscoelasticity), density and surface tension on droplet formation and impact.
• Understand the importance of the different substrate properties on the spreading of a droplet on a substrate.
• Obtain a basic idea about the effect of the time constants involved in flying, impacting, spreading, permeation, and drying.

Intended Audience: scientists and engineers interested in designing and tuning piezo inkjet print heads.

Course Description:
Piezo driven droplet-on-demand inkjet print heads consist of a large number of parallel integrated piezo actuated valve less pumps. Each pump is a series connection of a throttle (the connection to the main supply channel), a pump chamber, and a nozzle (the connection to ambient). Such pumps are acoustic cavities filled with ink and upon actuation pressure waves are generated in the ink. At the nozzle these pressure waves are transferred into a time dependent fluid velocity and ultimately in one droplet or more droplets (satellites). Droplet formation and drop impact are highly dynamical phenomena where inertia effects compete with surface tension and viscosity. Droplet formation depends on the pulse shape (height, rise time, dwell time and fall time, or more complicated shapes), the driving frequency, the layout of the pump, in particular, the dimensions of throttle, pump chamber, and nozzle and ink properties like viscosity (viscoelasticity), density, and surface tension. Dot formation depends on also flight time, the properties of the substrate, such as surface tension and permeability and the drying characteristics.

J. Frits Dijksman obtained his masters (1973) and PhD (1978) at the Technical University of Delft in The Netherlands. He worked with Philips Research Laboratories in Eindhoven, The Netherlands, for 32.5 years, mainly on inkjet printing, rheology of polymers, and medical devices. After his retirement he became part time professor in fluid dynamics at the University of Twente, The Netherlands. He is the author of a book  Design of Piezo Inkjet Print Heads (Wiley-VCH 2018). He is now emeritus professor. 



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