Shrinking bubbles and dancing cells: combining microfluidics and ultrasound for medical diagnostics and therapy

ROOM 125

Microbubbles are clinically used to enhance the contrast of ultrasound images, for the diagnosis of several heart diseases and cancers. Recently, nanobubbles–bubbles that are orders-of-magnitude smaller than microbubbles–have emerged as even more promising contrast agents for diagnostics applications due to their ability to extravasate from vessels into organ tissue. However, current state-of-the-art techniques to generate nanobubbles are unable to create uniform size nanobubbles, which limits the clinical efficacy of the nanobubbles. In this talk, I describe a microfluidic approach to produce monodisperse–uniform size–nanobubbles. We exploit the differential solubility of gases in aqueous solution to shrink microbubbles into nanobubbles. Namely, we use a two-component gas mixture of water-soluble nitrogen and water-insoluble octafluoropropane as the gas phase. We first generate microbubbles microfluidically, then allow the microbubbles to shrink, due to the dissolution of the water-soluble gas component, to achieve nanobubbles. We find that these nanobubbles show better homogeneity and brightness in both in vitro and in vivo ultrasound imaging experiments, in phantoms and in live mice, respectively, when compared with state-of-the-art bulk-made nanobubbles. These results suggest that the monodisperse nanobubbles may be suitable as ultrasound contrast agents for detecting nanoscale physiological leakages. The second half of this talk focuses on a newly discovered biophysical phenomenon, whereby adherent cells under the perturbation of an acoustic field self-generates microstreaming flows in a microfluidic channel. We find that the velocity of the microstreaming flow is a strong proxy for cellular mechanical properties, and that large molecule drugs can be selectively delivered into the cells via such microstreaming.

Dr. Scott Tsai is an Associate Professor in the Department of Mechanical and Industrial Engineering at Ryerson University, and an Affiliate Scientist at the Li Ka Shing Knowledge Institute of St. Michael’s Hospital. He obtained his BASc degree (2007) in Mechanical Engineering from the University of Toronto, and his SM (2009) and PhD (2012) degrees in Engineering Sciences from Harvard University. Dr. Tsai is the theme lead for Biomedical Delivery Systems at the Institute for Biomedical Engineering, Science, and Technology (iBEST), and he directs the Laboratory of Fields, Flows, and Interfaces (LoFFI). At Ryerson, Dr. Tsai is the interim director of the Biomedical Engineering Graduate Program. Dr. Tsai is a recipient of the United States’ Fulbright Visiting Research Chair Award (2018), Ontario’s Early Career Researcher Award (2016), Canadian Society for Mechanical Engineering’s I. W. Smith Award (2015), and Ryerson University’s Deans’ Teaching Award (2015). 

NOV 26 – Chen Gao – MECH Research Seminar Series

Chen Gao is currently working as a control system engineer in Honeywell Aerospace. She received her PhD in Aerospace Engineering from University of Toronto, Institute for Aerospace Studies in 2014. Her research interests focus on path planning, autonomous UAV systems, state estimation, and robotics.

Autonomous soaring surveillance in wind fields with an unmanned aerial vehicle

Small unmanned aerial vehicles (UAVs) play an active role in developing low-cost autonomous platforms. The success of the applications needs to address the challenge of the short endurance of UAVs. Inspired by nature where birds utilize various wind patterns to stay airborne without flapping their wings, designing an autonomous soaring UAV, which can utilize its surrounding wind patterns to wisely decide the most energy-efficient path during its mission, is an interesting topic and a practical concern in real world applications.

An integration of soaring and a large-scale surveillance mission is considered in this presentation. The static and dynamic soaring and associated surveillance strategies will be introduced for different application scenarios. The bird-mimicking soaring maneuver is designed for UAVs to not only improve flight endurance by extracting energy from surrounding wind environment, but also finish the designated surveillance task and provide the dynamic surrounding wind map to allow future soaring flight.

Keywords: UAV, autonomous soaring, surveillance, dynamic wind map, energy-efficient, path planning, nonlinear controller design.

See poster here



NOV 19 – Paula Meyer – MECH Research Seminar Series

Paula Meyer, P.Eng., holds her Bachelor, Master’s and Ph.D. degrees in Mechanical Engineering from McMaster University.  Dr. Meyer’s Ph.D. research was in vibrations and ultra precision machining.  Dr. Meyer worked in the automotive, nuclear and construction industries.  She was a senior contact engineer for General Motors of Canada Ltd., a senior engineer for AMEC NSS Ltd., and a project manager for RWDI.  Dr. Meyer is now a professor in Conestoga College’s Bachelor of Mechanical Systems Engineering Program, an accredited engineering degree program.

A Career in Industry and Academia

Dr. Paula Meyer will discuss her research in academia, and her career in industry.   Dr. Meyer will also describe Conestoga College’s current bachelor of Mechanical Systems Engineering program, where she is a professor.

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NOV 12 – Caroline Wagner – MECH Research Seminar Series

Caroline Wagner is a postdoctoral researcher in the Ecology and Evolutionary Biology department at Princeton University. She completed her PhD in Mechanical Engineering at the Massachusetts Institute of Technology (MIT), combining experimentation and mathematical modeling to study how the fluid mechanical properties of biological gels could be interpreted as indicators of the underlying biopolymer microstructure. Dr. Wagner’s current work focuses on modeling the nonlinear dynamics of infectious diseases, both at the population level and at the level of the in-host dynamics and biological processes regulating parasite transmission and suppression by natural immunity or vaccines. Dr. Wagner completed her B. Eng. at McGill University and her MS at MIT, both in Mechanical Engineering.

Mathematical disease models: from mucus rheology to infectious disease dynamics and control

The cross-linked polymeric microstructures of biological hydrogels give rise to their mechanical properties, which in turn contribute to their proper biological function. Quantification and modeling of the mechanical properties of these materials can provide insight into their microstructures, which is particularly important when structural changes are associated with impaired biological function. In the first part of this presentation, we will discuss this relationship between microstructure and mechanical properties in the context of the biological hydrogel mucus. To do so, we explore the network structure and association dynamics of reconstituted mucin gels using micro- and macrorheology in order to gain insight into how environmental factors, including pathogens and therapeutic agents, alter the mechanical properties of fully-constituted mucus. We then apply these findings to interpret changes in the mechanical properties of cervical mucus and saliva as biomarkers for disease. In the second part of this presentation, I will present plans for my current and future research directions, which include leveraging data sets in order to explore the complex forcing functions of nonlinear epidemic dynamics across the molecular-to-individual and the individual-to-global length-scales.

See poster here

OCT 29 – Mathilde Jean-St-Laurent – MECH Research Seminar Series

Mathilde Jean-St-Laurent is a Doctoral Candidate at Laval University supported by the National Science and Engineering Council of Canada. She has a Bachelor and a Master degree in mechanical engineering from Laval University. Her research interests are focused on composite materials for space applications and the development of new methods for testing composite materials in extreme environment. She is currently working on the effect of extreme low temperatures on the low velocity impact behaviour of composite sandwich panels for lunar exploration rovers. As part of her doctoral studies, she joined the Computational Mechanics Laboratory at University de Liège for one semester to acquire a specialization in modelling of damage in composite materials. Her Ph.D. is done in collaboration with the Canadian Space Agency and she was a research assistant for this institution for 4 months.

Composite Materials in Extreme Environment: Two Case Studies

Composite materials are increasingly used in the aerospace, automotive, and naval industries among others, since they offer excellent mechanical properties and a good performance to weight ratio. In all of those applications, they can be subjected to extreme environments. In flight, plane components are exposed to temperatures as low as -70°C. Low earth orbit satellites are subjected to extreme temperature variations from 150°C to -170°C. On the moon, during lunar nights, the temperature is approximately -150°C, and in some permanent shadowed areas temperatures can be even lower than -200°C. However, composite materials are sensitive to temperature variations, leading to the development of internal stresses. Moreover, temperature has an impact on the mechanical properties of composite materials, especially those governed by matrix behaviour. Two case studies are presented in order to highlight some of the challenges and research developments regarding composite materials in extreme environments. The first case study focuses on the effect of extreme temperature cycling on composite laminates and sandwich panels for the fabrication of satellites, and the second case study focuses on the effects of extreme low temperatures on the low velocity impact behaviour of composite sandwich panels for the fabrication of lunar exploration rovers.

Poster – Mathilde Jean-St-Laurent



Dr. Phillip Choi, Ph.D., P.Eng., Professor
University of Alberta, Department of Chemical and Materials Engineering, Edmonton, Alberta

Phillip Choi is Professor of the Department of Chemical and Materials Engineering at the University of Alberta and is a registered professional engineer in the province of Alberta and a Fellow of the Chemical Institute of Canada. Prof. Choi is also an active consultant to various multinational organizations on issues related to polymer products development and polymer failure analysis.
He received his BASc (1988) in chemical engineering from the University of British Columbia and his MASc (1992) and PhD (1995) from the University of Waterloo. His teaching and research interests lie in the areas of chemical thermodynamics and design/development of synthetic and bio-based polymers for food packaging applications, respectively.
He has authored and co-authored 3 book chapters, 103 referred journal publications and 1 US patent. He is also a coauthor of a textbook entitled “The Elements of Polymer Science and Engineering,” 3rd edition published by Elsevier. Prof. Choi was named the McCalla Professorship in 2007 and won the Faculty of Engineering Undergraduate Teaching Award in 2008 at the University of Alberta recognizing his dedication to undergraduate education. He received a National Young Innovator Award from Petro Canada Inc. in 2001 and an international IUPAC Travel Award in 2002, respectively, recognizing his work on polymer research.


Over the past several decades, the food packaging technology has improved dramatically. Such improvement is somewhat driven by the fact that packaged food needs to travel longer journeys from farms or factories to reach their consumers as well as to have longer shelf life.
This in turn puts great demands on packaging materials, particularly their barrier properties. A suitable packaging material must be able to protect food from oxygen (which causes oxidation and deterioration of the food), loss of carbonation, transport of moisture (loss or gain on moisture), contamination and infection, permeation of solvents and odours and flavours of the food, and absorption of flavour components by the packaging material. Obviously, selection of the right packaging material for the food item in hand is not a trivial task. And in many cases, polymers are the preferred materials.
In this seminar, he will present our recent studies on the barrier properties of a few food-packaging polymers. In particular, the discussion will be focused on how does the structure of such polymers affect the diffusivity of small molecules (e.g., water) using the techniques of molecular dynamics simulation and inverse gas chromatography.