Levich Institute Seminar – Tuesday, 02/27/2024

Tuesday, 02/27/2024
2:00 PM
Steinman Hall #312 

Professor Alicia Boymelgreen
Florida International University, Department of Mechanical and Materials Engineering

“Beyond Propulsion: The importance of Modelling the Metallic Coating of Active Colloids”


In an active system, elements draw energy from their surroundings and convert it to mechanical motion. Numerous examples exist in nature; from macroscale schools of fish to microscale bacterial colonies. Recently, attention has been drawn to a synthetic analog of these biological systems comprised of custom microfabricated colloids (1-10um in size) suspended in a bulk fluid, which can be activated in a variety of ways including surface chemical reactions and the application of external fields. Due to their small size, the particles move in the Stokes regime and in accordance with the scallop theorem, require some form of symmetry breaking to attain net motion. Most commonly, this is achieved through coating an inert microsphere with a partial metallic coating; the choice of which depends on the intended propulsion mechanism. For example, active colloids driven by asymmetric chemical reactions are coated in a catalyst such as Pt while electric field driven particles will be coated in a non-reactive conductor such as Au.

In this talk, we will examine two different ways in which modelling the metallic coating can enhance our understanding of experimental measurements of active colloid mobility. We begin with looking at electric field driven systems and demonstrate that the equilibrium orientation -and by extension the velocity – of active colloids is a function of the electric field properties (frequency, voltage) and the gravitational torque arising from the “bottom heaviness” of metallic coating. Secondly, we turn to catalytic active colloids, and demonstrate that mathematical models of the relationship between the size of the coating and active colloid mobility can offer insight into the nature of the chemical reactions occurring at the surface. The results of this work can be used to reduce discrepancy between theoretical models and experiment and optimize the design of active colloidal systems.

Alicia Boymelgreen is currently an Assistant Professor at Florida International University in Miami and heads the Interdisciplinary Microfluidics Lab (IML) there. She was born in Melbourne Australia and completed her B.Eng at Monash University. Dr Boymelgreen then travelled to Israel, completing her MSc in 2012 focusing on theoretical modelling of electrokinetically driven Janus spheres at Tel Aviv University under the advisement of Professor Touvia Miloh. Looking to validate these models experimentally, Dr Boymelgreen continued her PhD at the Technion -Israel Institute of Technology, in the lab of Professor Gilad Yossifon.


At IML, we currently have two very distinct research thrusts. The first focuses on active colloidal systems and particularly the role gravity plays in modifying both the individual and collective mobilities. In a totally different direction, we are also using microfluidic technology with integrated sensing to understand the impact of nanoplastics on early state development of marine species through in-situ real time observation.
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