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BEGIN:VEVENT
DTSTAMP:20260815T205940Z
LAST-MODIFIED:20121116T203436Z
DTSTART:20070823T150000Z
DTEND:20070823T160000Z
UID:event130@bu.edu
URL:http://physics.bu.edu/internal/events/show/130
SUMMARY:Ultrafiltration of macromolecules through nanopores
DESCRIPTION:Featuring Chi Wu\, The Chinese University of Hong Kong\nHosted 
	by: Ophelia Tsui\n\nPart of the Biophysics/Condensed Matter Seminar Series.
	\n\nAbstract: Using a special double-layer membrane to avoid interaction am
	ong flow fields generated by different pores\, we have\, for the first time
	\, observed the predicted discontinuous first-order transition in ultra-fil
	tration of flexible linear polymer chains. Namely\, the chain could pass th
	rough a pore much smaller than its unperturbed radius only when the flow ra
	te is higher than a certain value. When only one chain and one pore conside
	red in theory\, such a threshold is surprisingly independent of both the ch
	ain length and the pore size. Our results reveals that for a membrane with 
	many pores and at a microscopic flow rate  (q) lower than the threshold\, t
	he inevitable blocking of some pores by longer non-stretched coiled chains 
	increases q in those non-blocked pores because the macroscopic flow rate (Q
	) is a constant.  Our results reveal that the force to stretch a polymer co
	il in an athermal solvent is only ~10 fN. Further\, using this method\, we 
	are able to measure how "soft" a polymer chain is and how strong the inter-
	chain interaction is when they are collapsed and entangled with each other.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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