EXPERIMENTAL STUDIES OF PARTICLE ASSEMBLY INTO STREAMWISE BANDS

Yee, Andrew Joseph

Title:

EXPERIMENTAL STUDIES OF PARTICLE ASSEMBLY INTO STREAMWISE BANDS

dc.contributor.advisor	Yoda, Minami
dc.contributor.author	Yee, Andrew Joseph
dc.contributor.committeeMember	Alexeev, Alexander
dc.contributor.committeeMember	Sulchek, Todd
dc.contributor.committeeMember	Behrens, Sven
dc.contributor.committeeMember	Prakash, Shaurya
dc.contributor.department	Mechanical Engineering
dc.date.accessioned	2022-01-14T16:07:53Z
dc.date.available	2022-01-14T16:07:53Z
dc.date.created	2021-12
dc.date.issued	2021-09-01
dc.date.submitted	December 2021
dc.date.updated	2022-01-14T16:07:53Z
dc.description.abstract	Over the last twenty years, methods that use external forces to manipulate and arrange, or assemble, colloidal particles have become a research topic of interest with applications in microfluidics and nanotechnology. This research studies a novel method that uses a combination of Poiseuille flow driven by a pressure gradient, and electroosmotic (EO) flow driven by a voltage gradient, or electric field, to manipulate radius a < 0.5 mm polystyrene particles suspended at very low concentrations (<0.5 vol%) flowing through a microchannel. When the particles lead the flow due to electrophoresis, they are attracted to, and accumulate near, the wall. Above a minimum electric field, these concentrated particles ultimately assemble into “bands”: streamwise structures a few microns in diameter and a few cm long with a consistent transverse spacing. These structures are unique because they form in a flowing (vs. quiescent) suspension, which could lead to a method for continuous particle assembly. This thesis is an experimental study based on evanescent-wave visualizations to characterize how, and under what flow and conditions, these bands form. Bands form over a range of particle radii and zeta-potentials, near-wall shear rates, where the parabolic velocity profile for Poiseuille flow near the wall can be approximated by a constant shear rate, and electric fields. The bands are characterized in terms of the time for band formation, which appears to be scaled by the near-wall shear rate, and the average transverse period of bands over a ~200 mm square field of view. Estimates based on tracking individual tracer particles imply that near-wall particle concentrations increase 100- to 200-fold (compared with the bulk concentration) as the particles are attracted to the wall. Estimates of the wall-normal “lift” force that attracts particles from the bulk to the channel wall suggest that this force is comparable to the force predicted by models recently proposed by other researchers. Measurements of the streamwise near-wall particle velocities are significantly different from what would be expected, namely the superposition of the flow and particle electrophoretic velocities. If the flow velocity is, as expected, the superposition of Poiseuille and EO flow, these results suggest that wall effects greatly suppress particle electrophoresis.
dc.description.degree	Ph.D.
dc.format.mimetype	application/pdf
dc.identifier.uri	http://hdl.handle.net/1853/66071
dc.language.iso	en_US
dc.publisher	Georgia Institute of Technology
dc.subject	particle electrophoresis
dc.subject	lift forces
dc.subject	particle manipulation
dc.subject	particle assembly
dc.title	EXPERIMENTAL STUDIES OF PARTICLE ASSEMBLY INTO STREAMWISE BANDS
dc.type	Text
dc.type.genre	Dissertation
dspace.entity.type	Publication
local.contributor.advisor	Yoda, Minami
local.contributor.corporatename	George W. Woodruff School of Mechanical Engineering
local.contributor.corporatename	College of Engineering
relation.isAdvisorOfPublication	d318e6bc-95be-4fd2-bb0a-19fe480686df
relation.isOrgUnitOfPublication	c01ff908-c25f-439b-bf10-a074ed886bb7
relation.isOrgUnitOfPublication	7c022d60-21d5-497c-b552-95e489a06569
thesis.degree.level	Doctoral