Paper Number
MC5 

Session
Micro- and Nanofluidics and Confined Flows

Title
Growth and coalescence of nanoscopic mesas in stratifying, ultrathin freestanding films

Presentation Date and Time
October 11, 2021 (Monday) 5:25

Track / Room
Track 6 / Ballroom 1

Authors (Click on name to view author profile)

  1. Xu, Chenxian (UIC, Chemical Engineering)
  2. Yilixiati, Subinuer (Abbott, Process engineer III)
  3. Zhang, Yiran (10X Genomics, R&D Engineer)
  4. Sharma, Vivek (University of Illinois at Chicago, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Chenxian Xu1, Subinuer Yilixiati2, Yiran Zhang3 and Vivek Sharma1
1Chemical Engineering, University of Illinois at Chicago, Chicago, IL 60607; 2Process engineer III, Abbott, San Diego, CA; 3R&D Engineer, 10X Genomics, San Francisco, CA

Speaker / Presenter 
Xu, Chenxian

Keywords
confined flows; foams

Text of Abstract
Ultrathin (thickness < 100 nm) freestanding films of soft matter exhibit stratification due to confinement-induced structuring and layering of supramolecular structures like micelles and nanoparticles. Stratification in micellar films proceeds by the growth of thinner domains at the expense of surrounding thicker film, and local volume conservation leads to the formation of nanoscopic ridges at the moving front. The ridge often undergoes instability leading to the nucleation of nanoscopic mesas, that grow and coalesce over time. The shape and size of ridges and mesas in stratifying films are visualized and analyzed using interferometry, digital imaging, and optical microscopy (IDIOM) protocols, with unprecedented high spatial (thickness < 100 nm, lateral ~500 nm) and temporal resolution (< 1 ms). In this contribution, we analyze the shape evolution and coalescence of mesas in an effort to develop a comprehensive understanding of drainage by stratification in micellar foam films, including the role played by the contribution of supramolecular oscillatory structural forces to disjoining pressure. We present the theoretical analysis of flows under confinement using a thin film equation amended with oscillatory structural disjoining pressure and discuss how the interplay of hydrodynamics and thermodynamics dictates the drainage flows in foam and soap films.