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CATEGORIES:Engineering Fluids Group Seminar
SUMMARY:Self-assembled Precipitate Membranes and the Impli
 cations for Life - Yang Ding (Department of Chemic
 al Engineering\, University of Cambridge)
DTSTART;TZID=Europe/London:20181123T130000
DTEND;TZID=Europe/London:20181123T140000
UID:TALK112414AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/112414
DESCRIPTION:Far from the thermodynamic equilibrium\, many prec
 ipitation reactions can create complex membrane st
 ructures.   Such membranes are of great research i
 nterest in fields ranging from chemical engineerin
 g to geophysics\, and even biology where they are 
 thought to have played a vital role in the origin 
 of life. Usually\, the transport of chemicals by c
 ombined buoyancy\, osmotic and diffusive mechanism
 s\, support the precipitation reaction. In order t
 o study these transport processes across a growing
  selective membrane\, we use a chemical-garden rea
 ction in a micro-fluidic reactor. We focus on two 
 studies in a horizontal Hele-Shaw cell:  one where
  the flow is driven by the membrane itself and ano
 ther where flow is forced by a pump. In the first\
 , we examine the changes of the membrane morpholog
 y associated with the concentration of reactants. 
 We also survey the growth rate of membrane\, which
  is determined by the osmotic flow as well as by c
 oncentration effects. The motion of the fluid is v
 isualized in order to understand the transport pro
 cess. The pressure inside the membrane structure i
 s measured and different patterns of pressure chan
 ges are identified. A pressure-concentration model
  is proposed to explain the harmonic pressure chan
 ges of this system. In the second study\, with ext
 ernally-forced flow\, the growth of a wavy precipi
 tate membrane is observed.  We establish that its 
 growth is controlled by transverse diffusion and d
 ispersion of ions. We develop a precipitation mode
 l\, taking into account diffusion of ions through 
 the precipitate and through an adjacent gel layer.
  Results from our theory are in excellent agreemen
 t with the measurements\, and show that a wavy pre
 cipitate surface can enhance the transverse transp
 ort of ions.
LOCATION:JDB Seminar Room\, CUED
CONTACT:Joseph Ibrahim
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