Lorentz Center - Contact Line Instabilities from 4 Jan 2010 through 8 Jan 2010
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    Contact Line Instabilities
    from 4 Jan 2010 through 8 Jan 2010

 
Contact line instabilities, January 4-8 2010

SCIENTIFIC REPORT

 

Motivation

The newest industrial technologies in producing most accurate imaging at micro and nano scales, such as nano-lithography and micro inkjet printing, have opened up a plethora of unsolved issues in further development of the machines to realize these technologies. Many of these issues find their origin directly in the contact line instabilities at the interface of liquid, gas and solid at micro and smaller scales. The physical mechanisms behind these instabilities are very diverse in nature and raise a number of fundamental challenges. The aim of the workshop was to provide a bridge between the industrial and academic worlds, connecting technological challenges to the latest experimental and theoretical findings on contact line instabilities. The workshop also links the FOM-Industrial Partnership Program on wetting dynamics to the international scientific community.

 

The workshop

The workshop was attended by 71 people from 10 countries, and enjoyed a mixed audience of leading scientists, young researchers and representatives from industry (ASML, OCE, Philips, SKF). Among the keynote speakers were: Andreotti (Paris), Bocquet (Lyon), Eggers (Bristol), De Coninck (Mons-Hainault), Limat (Paris), Pomeau (Paris), Quere (Paris). The main industrial and fundamental challenges were outlined by lectures during the first days of the program. This was followed by thematic workshops on the following specific topics:

 

  • Air entraiment
  • Inkjet printing
  • Surface tension gradients
  • Film breakup

 

These sessions were very instrumental in generating open discussion and turned out a key part of the meeting. In addition, the program contained many talks by PhD students and postdocs.

 

Outcome of the workshop

 

Several latest scientific and industrially related subjects were presented and intensively discussed. Some of the noteworthy findings are summed below:

 

  • Liquid layer break-up for layer thickness of the order of micron (or 0.1 micron) was discussed next to recent findings on this phenomenon at nano size thicknesses. It turns out that the nucleation for relatively thick layers is still a moot question that should be researched more. Specially the micron size is of considerable importance for immersion lithography. Some new contacts have been made between ASML and a few academic centers, Thiele (Loughborough University), Rauscher (Max-Planck-Institut fuer Metallforschung in Stuttgart) together with a PhD project at University of Eindhoven (Darhuber) to understand and model this phenomenon.
  • Possible similarity was observed in the transition mode at critical speed during pulling of a plate from a liquid bath and the critical speed observed in immersion lithography.  The phenomenon was shown with recent findings by Eggers. A follow-up will be started in co-operation between ASML (Riepen) and University of Twente (Snoeijer).

 

  • Valuable findings were shown when comparing pearls formation at sliding drops (Limat) and the water loss under a needle for immersion lithography (Winkels, Snoeijer, Riepen). Large similarity was shown quantitatively. It was also shown that at high speed the 3D structure becomes very dominant and deviation from 2D solutions is very large. The behaviour of top curvature of the sliding drop is very important in this analysis.

 

  • For inkjet printing several not well-understood phenomena were discussed and contacts for further research were successfully made. Some of mentioned phenomena were: collision between free surfaces; Inclusion of air pockets and parameters determining contactline pinning and the nozzle outlet.

 

  • Some latest results on Leidenfrost effects or similar phenomena were shown by Quere on surfaces that have special structures and where the size of the profile structures on the surface are of importance. These can also be used in immersion lithography where removing undesired drops on certain surfaces is needed. Some new activities have recently been started on this subject at ASML.

 

  • Splashing phenomena were shown to be highly dependent not only on surface geometry and chemistry but also on surrounding pressure level of the drop.

 

  • New contacts were made for contribution to another Lorentz workshop in May on capillary shaping of solutes, deposition of particles etc.

 

Many of the above-mentioned discussions showed that still critical issues exist in film pulling, pinning, marangoni effects, teapot effects, splashing and coalescence that are apt for a new workshop later with more industrial applications. The goal of providing a bridge between industrial and academic world on the subject of contact line instabilities was well achieved during this workshop.

 

We thank the Lorentz Center for their excellent support both from organizational as well as financial aspects.

 

 

 

Detlef Lohse (University of Twente, The Netherlands)

Jacco Snoeijer (University of Twente, The Netherlands)

Ramin Badie (ASML Netherlands BV, The Netherlands)

Michel Riepen (ASML Netherlands BV, The Netherlands

Hans Reinten (Oce Technologies BV, The Netheralnds)

Herman Wijshoff (Oce Technologies BV, The Netherlands)

 



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