Waitukaitis Group

Soft and Complex Materials

The Waitukaitis Group is an experimental physics lab whose research focuses on complex phenomena occurring in solids and liquids. Under this general umbrella, their lab addresses a variety of topics ranging from the nanoscale to the macroscale and involving techniques ranging from atomic force microscopy to high-speed imaging.

An example at the smallest scale is the phenomenon of tribocharging – the exchange of electrical charge between objects during contact. Although well-known to anyone who has been shocked by a doorknob and described scientifically going back as far as ancient Greece, the underlying mechanism for tribocharging remains unresolved. They are particularly interested in same-material tribocharging, which counterintuitively occurs when identical materials are brought into contact. Recent results suggest that this phenomenon might be caused islands of water on the surfaces of materials. Using atomic force microscopy to characterize surfaces and several cutting-edge techniques to measure charge exchange, a major goal is to validate or nullify this hypothesis.

At larger scales, they are interested in the non-Newtonian dynamics that arise when colloidal-sized solid particles are suspended in liquids. Perhaps the most well-known example is a dense mixture of cornstarch particles in water, which behaves liquid-like when perturbed gently but solid-like when vigorously agitated. Previous work has centered on passive non-Newtonian suspensions such as this, but moving forward their lab will focus on colloidal suspensions filled with particles whose motion can be controlled by environmental stimuli. Their long-term goal in this direction is to be able to control the flow of fluids using the motion of active constituents.