MANIPULATING SMALL DROPLETS IN MICROCHANNELS WITH COMPLEX FLUIDS - PowerPoint PPT Presentation

JUNE 5, 2019 MANIPULATING SMALL DROPLETS IN MICROCHANNELS WITH COMPLEX FLUIDS Blue Waters Symposium 2019 MICHAEL P . HOWARD The University of Texas at Austin I use Blue Waters to engineer complex fluids and soft materials at the nanoscale.

Manipulating particles in microchannels - filtration - fractionation - cell sorting - oil recovery - water treatment How can we systematically engineer these processes? 2 Di Carlo et al., PNAS 104 , 18892 (2007).

Complex fluids 3

microscopic macroscopic 4 × 10 0 ρ =0.025 (a) κ =0 ρ =0.050 ρ =0.100 η / η s 10 0 10 10 -5 10 -4 10 -3 10 -2 . γ A. Nikoubashman and M.P. Howard. Macromolecules 50 , 8279 (2017). 4

Cross-stream migration Addition of a viscoelastic component induces migration in Poiseuille flow flow ß distance down channel What happens when the particles become “small”? D'Avino et al., Lab Chip 12 , 1638 (2012). 5

Cross-stream migration at the nanoscale Comparable length scales Brownian motion PEO R e ~ 300 nm Kim et al., Lab Chip 12 , 2807 (2012). Prohm et al., Eur. Phys. J. E 35 , 80 (2012). Average force on particles 〈 F x 〉 gives average direction of movement 〈 F x 〉 < 0 〈 F x 〉 = 0 〈 F x 〉 > 0 6

Mesoscale modeling s Constitutive resolution models ms time scale Coarse-grained & μs mesoscale models ns Atomistic models speed ps fs μm nm mm length scale 7

Coarse-grained models bond dispersion forces, excluded stretch volume, electrostatics angle bend dihedral twist 8

A. Nikoubashman et al., J. Chem. Phys. 140 094903 (2014). M.P. Howard et al., J. Chem. Phys. 142 , 224908 (2015). What happens if the particles are droplets or cells that deform? 9

Droplet migration F = F C + F R + F D repulsive random drag force force force 10

Why Blue Waters Large parametric design space Large coarse-grained model 4 polymers 384,000 particles x 3 polymer concentrations = 4 GPUs for 48 hours x 5 flow rates x 5 replicas (HOOMD-blue) Blue Waters is the only system available to us with the GPU resources needed! 11

Droplet in a neat solvent is different from a rigid particle f x [ ε /d ] no polymer 6 0 . 001 inward 0 . 002 probability 0 . 003 4 0 . 004 0 . 005 2 (a) 0 0 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 | z c | /H M.P. Howard et al., Soft Matter 15 , 3168 (2019). 12

<latexit sha1_base64="ZFeXCJkpmc0L/fmZSvzcO2cZU8=">AB/HicbVDLSsNAFL3xWesr2qWbwSIYklU0I1QqgsXVSwD2hDmUwn7dDJg5mJEL8FTcuFHrh7jzb5y2WjrgQuHc+7l3nvciDOpLOvbWFpeWV1bL2wUN7e2d3bNvf2WDGNBaJOEPBQdF0vKWUCbilO5Gg2Hc5bvjm4nfqRCsjB4UElEHR8PA+YxgpW+mbpFl2jnicwSeuntSytn9Syvlm2KtYUaJHYOSlDjkbf/OoNQhL7NFCEYym7thUpJ8VCMcJpVuzFkaYjPGQdjUNsE+lk06Pz9CRVgbIC4WuQKGp+nsixb6Uie/qTh+rkZz3JuJ/XjdW3pWTsiCKFQ3IbJEXc6RCNEkCDZigRPFE0wE07ciMsI6CaXzKuoQ7PmXF0nrGKfV6z7i3K1lsdRgAM4hGOw4RKqcAcNaAKBJ7hFd6MJ+PFeDc+Zq1LRj5Tgj8wPn8AupiTiA=</latexit> Droplet shape depends on the local flow 0 . 6 f x [ ε /d ] 0 . 001 B 0 . 002 0 . 4 0 . 003 D = L − B ⟨ D ⟩ 0 . 004 L 0 . 005 0 . 2 L + B (a) 0 . 0 40 𝜄 ⟨ θ ⟩ [ ◦ ] 30 20 (b) 0 . 0 0 . 1 0 . 2 0 . 3 Ca M.P. Howard et al., Soft Matter 15 , 3168 (2019). 13

CIXicbVDLSgMxFM34rPV dekmWIS6KTMq2GXRjcsK9gGdsWTSTBuaeZDcEeswv+LGX3HjQpHuxJ8x0w6orRcCJ+fc 5N73EhwBab5aSwtr6yurRc2iptb2zu7pb39lgpjSVmThiKUHZcoJnjAmsB sE4kGfFdwdru6CrT2/dMKh4GtzCOmO TQcA9Tgloqleq2UBibCvuY1swDyq2JwlN7IhI4ETguPeQ/tweU1vywRBO7rS1bFbNaeF YOWgjPJq9EoTux/S2GcBUEGU6lpmBE6STa CpU 7ViwidEQGrKthQHymnGS6Y qPNdPHXij1CQBP2d+OhPhKjX1Xd/oEhmpey8j/tG4MXs1JeBDFwAI6e8iLBY QZ3HhPpeMgh rQKjk+q+YDomOCHSoR 2CNb/yImidVq2zqnlzXq5f5nEU0CE6QhVkoQtUR9eogZqIoif0gt7Qu/FsvBofxmTWumTkngP0p4yvb8hJpIY=</latexit> <latexit sha1_base64="MhFg8rnhmrAZlipHUD0ju739lvs=">A Flow and droplet position depend on polymer concentration Solution is non-Newtonian for higher Droplet moves inward with increasing polymer concentrations. polymer concentration. . ✓ ∂ u x ◆ n (b) φ p = 5 . 0% φ p = 10 . 0% no polymer 8 τ ∼ 1 . 5 ∂ z φ p = 2 . 5% φ p = 7 . 5% 6 u x [ d/ τ ] 2 probability 1 . 0 1 4 φ p = 7 . 5% no polymer 0 0 . 5 0 . 5 0 . 7 0 . 9 φ p = 2 . 5% φ p = 10 . 0% 2 φ p = 5 . 0% 0 . 0 0 − 1 . 0 − 0 . 5 0 . 0 0 . 5 1 . 0 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 z/H | z c | /H center wall M.P. Howard et al., Soft Matter 15 , 3168 (2019). 14

Conclusions Polymer solutions can be used to manipulate droplets in microchannels. Droplet position and shape depend on the polymer solution and flow. Important for applications like membrane filtration or cell sorting. M.P. Howard et al., Soft Matter 15 , 3168 (2019). All software has been released open source on GitHub: mphoward/azplugins 15