Measuring Thin Film Flows Using FRAP

Web Published:

Measuring Thin Film Flows Using FRAP

(Fluorescence Recovery After Photobleaching)

Princeton Docket #14-2963


Industrial coating, painting, and printing processes all involve a thin liquid film flowing over a solid surface. To properly design an industrial system containing these processes, it is necessary to understand the characteristics of the flow in these films. Current methods, such as Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV) techniques, are limited in their practicality and usefulness. These techniques both require expensive specialized equipment and complicated post-processing.  In addition, PIV potentially disrupts the flow itself by the addition of tracer particles.


Researchers in the Department of Mechanical and Aerospace Engineering at Princeton University have developed a new technique to measure the flow in thin liquid films that is non-invasive (i.e. no particles) and simpler to implement than prior techniques.  By exploiting established flow characteristics of thin viscous films, simple macroscopic measurements of a film can be made and extrapolated detailed information about the microscopic flow characteristics can be inferred.


This novel technique also allows for the measurement of flow in films that are far thinner than those which can be measured with prior techniques.  In a proof-of-concept experiment, the flow in a film that is 2 microns thick has been measured, and one could potentially measure films that are even thinner.



·         Manufacture of semiconductors and photovoltaics


·         Materials processing


·         Industrial coating, painting, and printing



·         Simple set-up


·         Inexpensive, non-specialized equipment


·         Particle-free


·         Simple image processing and data analysis


·         Measures flow in ultra-thin films not measurable by any other technique


Howard Stone is the Donald R. Dixon '69 and Elizabeth W. Dixon Professor in Mechanical and Aerospace Engineering at Princeton University.  His research has been concerned with a variety of fundamental problems in fluid motions dominated by viscosity, so-called low Reynolds number flows, and has frequently featured a combination of theory, computer simulation and modeling, and experiments to provide a quantitative understanding of the flow phenomenon under investigation.  Prof. Stone is the recipient of the most prestigious fluid mechanics prize, the Batchelor Prize 2008, for the best research in fluid mechanics in the last ten years.  He is also a Fellow of the American Academy of Arts and Sciences and is a member of the National Academy of Engineering.

Jason Wexler is a 4th year PhD student in Howard Stone’s group, who obtained his BS in Mechanical Engineering from UC Berkeley in 2008. His research at Princeton has focused on understanding small-scale flows using a combination of theory and experiments.  Before Princeton he worked as a design engineer for industry giant SunPower, developing strategies to mitigate wind loads on solar panels.


Ian Jacobi is a post-doctoral research fellow in Howard Stone’s group, who obtained his BS in Chemical Engineering from MIT and his MS and PhD in Aeronautical Engineering at Caltech. His research is primarily directed at the structure and behavior of turbulent boundary layers and other wall-bounded flows for the purpose of designing physics-based drag reduction and flow control strategies. More recently, he has been investigating the use of small-scale flows and micro-manufactured surfaces for solving both small- and large-scale fluid engineering problems.


Intellectual Property Status

Patent protection is pending.

Princeton is seeking to identify appropriate partners for the further development and commercialization of this technology.


Michael R. Tyerech
Princeton University Office of Technology Licensing • (609) 258-6762•

Laurie Bagley
Princeton University Office of Technology Licensing • (609) 258-5579•




Patent Information:
For Information, Contact:
Michael Tyerech
former Princeton Sr. Licensing Associate
Princeton University
Jason Wexler
Ian Jacobi
Howard Stone