Prsentation PowerPoint

Activity measurements at the microfluidic scale: towards osmotic pressure measurements1

GDR CNRS AMC2October 20-22, SteZIANE NadiaSupervisors: J. Leng and JB. SalmonIntroductionDialysis process: Perfect control of the environment Concentration of non-volatile solutes in aqueous solutionsTowards phase diagrams

Microfluidics interests:Linear geometryEasy observations of confined volumeEasy analysis and fast experiments

2Microfluidic chip3

PDMSPDMS membranee = 30 40 mglass slide rectangular channelw = 50 60 mh = 30 40 mL0 = 1,5 3 cmL0 hnLRandall and al., 2005Salmon and Leng, 2010 Water pervaporation4

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Channel geometry: confined drop5Step 1Fill dead-end microchannels Step 3Evaporation of confined dropletsStep 2Injection of a fluorinated oil or airL0 = 1,5-3 cm

60 mNoblin and al., 2008Simple model for solutions and dispersions6

Continuous and uniform concentration (t) = 0 L0 /L(t)

Evaporation rate controlled by activity Hypotheses:

No initial gradientsPe = hV/D < 1 no vertical gradientsPervaporation rate uniform along xQuasi steady regime for water pervaporation6

Absorbance measurements7 Bleu brillant FCF at 0,1 mM (10x) No gradients for molecular solutions200 m

Fluorescence meausurements8Fluorescent latex (40x)Gradients at x=0 : evidence of leakage velocityDiameter = 20 nm

J. Angly and al., 2012x=0x=Lg50 m

Fluorescence meausurements9Gradients at x=0 : evidence of leakage velocity

Gradients at x=Lg : is not true

Fluorescent latex (40x)Diameter = 200 nm hTD = h/DT = h/Vx=0x=Lg50 m9Pure water 10

Time ~ 1h30 Image analysisPure water 11

Accurate estimation of humidy using 1D modelVf ~ 0,52 m/sTe ~ 1500 sBinary water/glycerol mixture12

Water/glycerol 2% v/vRoom humidity = 60%h = 26 m, time ~ 2 hrNinni and al., 2000

Binary water/glycerol mixture13

Te ~ 2200 s

Binary water/glycerol mixture14

Binary water/glycerol mixture15

Conclusion & outlooksRobust measurements of the activity of aqueous solutions at the nanoliter scale

New chip design

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17Estimation of liquid-liquid transition of ternary system PEG/water/ammonium sulfate Conclusion & outlooksPEG: 5% w/w

Ammonium sulfate:5% w/wTime ~ 1h20 Conclusion & outlooks18

Development and characterization of new microfluidic devices including dialysis membranes

Control of osmotic exchanges at a nanoliter scale

Quantitative measurements of thermodynamic properties of complex fluidsMicrodialysis processHsieh, 2007Jensen and al., 2008Thank youQuestions ?19