Research
Current and Ongoing Projects
"Directed Motion of Janus Particles"
(ongoing research, enabled by our NSF Scalable Nanomanufacturing Program)
More information on this current research here:
"Studying Deposition of Hair Care Ingredients Using High-Speed Confocal Microscopy"
Pennsylvania Infrastructure Technology Alliance w/ Dow Chemical Co. (Dr. John Riley)
Details to follow...
"ISS: Thermophoresis in quiescent non-Newtonian fluids for bioseparations"
National Science Foundation
with: Professor Xuanhong Cheng and Professor Kelly Schultz
There are many natural and industrial processes where nanoscale particles suspended in a fluid move as a result of a temperature gradient known as thermophoresis. Thermophoresis impacts a wide variety of processes, such as drug delivery and bioseparations utilized for detecting viruses. However, our current understanding of thermophoresis is limited. Prior experimental studies have conflicting evidence, making the determination of the fundamental mechanisms that drive particle motion difficult. Very few prior studies have considered the motion of these particles in more complex fluids and gels. One key limitation is that it is difficult to separate the impact of thermophoresis from thermally-driven fluid flow that results from fluid recirculation due to temperature-dependent fluid density and gravity. To overcome this limitation, this project will pair terrestrial experiments with those in microgravity onboard the International Space Station (ISS) where buoyancy-driven flow is negligible. The goal is to determine the fundamental physics and chemistry driving thermophoresis in both simple and complex fluids, and use this information for enhancing viral separation platforms by optimizing fluid properties. In an era when disease control is influencing the lives of everyone on Earth, this work will focus on developing enhanced and robust microfluidic viral-load detection devices.
"EAGER: Microscale Fingering Instabilities in Drying Colloid and Polymer Films"
National Science Foundation
This research investigates a visually striking fluid flow instability in colloid-polymer thin films during drying found using high-speed confocal laser scanning microscopy. This is the first observation of a fingering instability of polymer solutions at micron or sub-micron length scales in porous materials such as colloidal crystals. Fingering instabilities, such as the Saffman-Taylor instability, have had broad impacts for transport in porous media for secondary oil recovery and aquifer transport. Most studies of the Saffman-Taylor instability focus on the displacement of one higher viscosity Newtonian fluid with an immiscible lower viscosity Newtonian fluid in either a Hele-Shaw cell or a porous material. The knowledge gained will be used to control or suppress the formation of fingers in order to alter the properties of these films. These fingers may be ubiquitous in drying thin films of particles in viscous liquids and may have a strong impact of the adhesion of these films to their substrates. These structures will be investigated and utilized in the fabrication of nanoscale or microscale networks of fluid channels for devices.
"GOALI: Collaborative Research: Non-invasive measurement of kinematics and rheology in a non-equilibrium drying complex fluid"
National Science Foundation, Case Western Reserve University, and PPG
Lead: Professor Christopher Wirth, Case Western Reserve University
Coatings impact many applications, including consumer products, medicine, food, and engineering applications, typically serve one of three purposes: to protect and extend the life of a product, to improve aesthetics, or to add new functionality. Small defects that form during solidification of a fluid film coating can harm the ultimate functionality of the coating. In a single automotive plant, painting accounts for 60% of the energy consumption, and refinishing to repair defects can cost more than $10 million/year. There are few methods capable of non-invasive tracking of the coating properties during drying. The objective of this project is to develop the capability to measure the transient viscosity and flow of a drying coating with time- and space- resolved optical measurements. The underlying knowledge gained via this project in relation to how transient rheology affects fluid flow will be applicable to a multitude of coating manufacturing processes. The project will have significant impact on coatings design and processing, help to bridge the gap between academia and industry, and include outreach to the science, technology, engineering, and math communities.
Lead: Professor Xuanhong Cheng, Department of Bioengineering
Bionanoparticles, such as viruses and vesicles, are commonly concentrated in clinical diagnosis, defense surveillance and food safety monitoring. Conventional methods, such as high-speed centrifugation and nanofiltration, are instrument and labor intensive and unpractical under resource-limited conditions. These challenges motivate the researchers to create a novel microfluidic solution for nanoparticle processing. Success of the proposed research will have broad practical impact in viral sample processing for clinical diagnostics of infection, homeland security surveillance and food safety monitoring.
"Custom Particle Development"
Johns Hopkins University Applied Physics Laboratories
Past Projects
(Updates ongoing)
"SNM: Technologies for Nanoparticle Monolayer Self-Organization and Deposition "
National Science Foundation
with Mark Snyder, Xuanhong Cheng, and Nelson Tansu
This research seeks to advance the fundamental manufacturing science of nanoparticle monolayer self-assembly and deposition as a unit operation for commercial nano manufacturing. Specifically, the proposed project will investigate the fundamental aspects of self-assembly methods, incorporate these discoveries into continuous roll-to-roll commercial-scale processes, and develop novel applications that utilize these processes. These processes will enable production of nanoporous membranes, flexible dye sensitized solar cells (DSSCs), and light emitting diodes (LEDs).
"Mixing, Migration, and Structure of Suspensions in Pressure-Driven Flows "
National Science Foundation
Suspensions of a moderate particle volume fraction tend to demix in nonlinear shear. Although this effect has been studied extensively in simple flows to determine how suspension rheology results in migration, few studies have considered how migration occurs in more complicated flows. Migration in industrial processes has long complicated process development and has become increasingly important as researchers strive to process and analyze blood and other biological suspensions in complicated BioMEMS flows. The objectives of this research were to broaden our fundamental understanding of flowing suspensions by considering how the fundamental symmetries within flows interplay with the underlying suspension structure. In 1D, 2D and 3D microchannel flows commonly used in BioMEMS, the competition between suspension demixing via shear migration resulting from multibody hydrodynamic interactions and chaotic advection generated within microchannels designed to enhance mixing will be investigated. Direct measurement of flow and concentration profiles will be performed using high speed 3D confocal laser scanning microscopy (CLSM). This technique, coupled with a flow-stop-scan protocol, allows direct measurement of suspension structural anisotropy that generates the normal stresses that result in migration. These studies were extended to examination of technologically relevant fluids, including polydisperse suspensions, electrostatic-stabilized suspensions, suspensions in viscoelastic media, and whole blood.
"Investigation of Microsphere Convective Deposition for Photonic and Biological Applications"
National Science Foundation
with Xuanhong Cheng and Nelson Tansu
Although colloidal convective deposition is used in many technologies, the fundamental physics is poorly understood. This research generated a fundamental description of the physics involved in the deposition of a monolayer of particles using convective self-assembly. Drawing an evaporating meniscus across a substrate, a process related to the "coffee ring effect" and the Langmuir-Blodgett technique, forms a structure of particles ranging from random and ordered sub-monolayer to well-ordered multilayers. Through this research, the importance of controlling this microstructure will be demonstrated in two applications that have significant potential impact on their respective industries. First, the microlens arrays fabricated using this technique have the potential to surmount the current state-of-the-art LED photon extraction, allows scale-up for industrial applications, and is low-cost as compared to current techniques of surface patterning via electron beam lithography. In whole blood analysis, this technique can be generalized for a variety detection schemes and will aid development of a process that aims to bring low cost detection to regions lacking proper medical resources. This work will directly provide both graduate and undergraduate educational opportunities in an area at the convergence of several technologically-critical research areas including microfluidics, suspension transport, photonics, and bioengineering.
More to be added...
