Jet formation and control in laser induced forward transfer printing of liquid inks

March 22, 2018

March 22, 2018
Craig B. Arnold 
Princeton University 
2:00 - 3:00pm
SEH, B1220



Laser induced forward transfer (LIFT) has become a well-recognized technique for depositing small amounts of material for microscale additive patterning.  In this technique, a thin film of ink is ejected from a sacrificial substrate using a short pulsed laser and the resulting material is propelled forward to the desired substrate.  Depending on the combination of incident laser power and ink properties, it is possible to observe different transfer regimes including single droplet, multiple droplet and particle spraying.  However for optimal materials patterning, the single droplet regime is optimal.  In this study, we offer criteria to separate different transfer regimes by comparing the time scales of the effective forces acting on the ink material. We demonstrate that one can define a “characteristic shear rate” for the problem, and the evaluate shear-rate dependent viscosity accordingly. The calculated effective Ohnesorge number combined with the viscosity value obtained using this characteristic shear rate offers a good criterion to predict the parameters needed for the ideal printing regime.  Experiments also show that higher Deborah number is another way to suppress multiple droplet formation. It is shown that while increasing viscoelasticity reduces capillary instabilities, inertial effects should be reduced for optimum printing.



Craig B. Arnold is a Professor of Mechanical and Aerospace Engineering at Princeton University and the director of the Princeton Institute for Science and Technology of Materials.  His research ranges from basic science to applied technology aimed at developing a deeper understanding of fundamental materials synthesis and processing with interests in energy storage systems, laser materials processing and advanced optics.  He earned his PhD. in condensed-matter physics from Harvard University, and was an NRC post-doctoral fellow prior to joining the faculty at Princeton in 2003.  He has earned numerous accolades for his work in materials processing including the Edison Patent Award, an R&D 100 award, the Laser Focus World-OSA technology innovation award, and the SPIE PRISM award for photonics innovation.  Prof. Arnold is a fellow of OSA and SPIE.