20:13 PM

A Solid Understanding of Liquid-Solid Interaction

Pitt Researcher Receives $300K from the NSF to Explore Motion of Viscous Liquids Interacting with Solid Bodies

The same principles that led to the Tacoma Narrows Bridge collapse in 1940 could someday allow doctors to direct microrobots through the bloodstream to deliver medicine precisely where needed.  

The interaction between viscous liquid and solid bodies has become a main focus of applied research, and with good reason. G. Paolo Galdi, distinguished professor of mechanical engineering and materials science at the University of Pittsburgh Swanson School of Engineering, is working to harness the potential of this interaction for wide-ranging applications in biomedical engineering, micro- and nano-technological equipment design, and suspension bridge construction. The National Science Foundation (NSF) recently awarded Galdi $299,792 for this work.

Galdi's project investigates  two specific aspects within this field. The first explores how a solid object moves when it vibrates in a viscous liquid, especially when the vibration is caused by an oscillating mass inside the object. This work has practical applications in biomedical engineering and designing small-scale equipment.

“A microrobot with a vibrating motor could be used to deliver medicine directly to where it’s needed in the body, as long as the robot’s movement could be precisely controlled,” explained Galdi. “An internal, vibrating motor would be much safer than other means of propelling something within the veins, but the movement from a vibrating motor is much more difficult to predict and control.”

Galdi’s research aims to discover how changing the frequency of vibration relates to the net motion of the robot, and how changing the shape of the robot and the speed of the vibration might direct its path.


The Tacoma Narrows Bridge, nicknamed “Galloping Gertie” for its undulating movements, before it collapsed in 1940.


The second aspect of Galdi's research examines how the flow of a viscous liquid can affect or even produce the oscillation of an elastic structure. Understanding this phenomenon is crucial for studying the stability of suspension bridges. By investigating these questions, Galdi hopes to contribute to preventing disasters like the Tacoma Narrows Bridge collapse, a suspension bridge that famously collapsed soon after it was built in 1940 because of oscillations caused by wind. 

“When wind hits a suspension bridge, it can create oscillations that can provoke movement of the structure and, sometimes, cause it to fail. This failure isn’t as simple as it appears,” explained Galdi. “I’m approaching this problem from a rigorous mathematical perspective so that, hopefully, we can prevent these catastrophes in the future.” 

The NSF funding not only recognizes the importance of Galdi's research but also creates opportunities for graduate students. The grant will provide valuable research experience to ECE PhD Candidate Marc Karakouzian. Two undergraduate students—Benjamin Carr and Oscar Gerber—will also contribute to the work.

The three-year project is set to begin on July 1.