James Bird

How Do Micro and Nanoparticles Deposit on a Surface Following Oblique Impact and Drop Drying?

PROJECT DESCRIPTION
This project investigates the fluid dynamics of droplets. When spraying plants with pesticides or coating a surface with functional inks, an effective way to deposit micro- and nanoparticles onto a surface is to suspend the particles in a droplet, impact the droplet on the surface, and then let the droplet dry. The deposition is typically non-uniform due in part to the coffee-ring effect, a phenomenon by which the evaporating drops draws liquid and the suspended particles to the contact line. Most research has focused on drops impacting vertically on a horizontal surface. Yet in many situations, the drop will impact obliquely, and the surface may be inclined relative to gravity. This project aims to characterize the influence of surface and impact orientation on the deposition non-uniformity.

LABORATORY MENTOR
Garam Lee

RESEARCH GOALS
– Predict the deposition thickness profile based on the concentration, particle size, droplet size, impact angle, and velocity.
– Determine if particle size influences the deposition through either inertial or gravitational effects.
– Evaluate whether such a colloidal system mimics dried blood stains and with the goal of improving forensic analysis.

LEARNING GOALS
– Learn how to make colloidal suspensions and measure their viscosity, surface tension, density, and contact angle on a surface
– Learn how to operate a high-speed camera and measure the thickness profile of a stain
– Learn image processing techniques to extract parameters from the high-speed images
– Learn how to analyze the measurements to search for correlations and test scaling hypotheses
– Learn best practices in poster presentations

Learn more about Associate Professor Bird on his faculty page.