TY - JOUR
T1 - Microfluidic production of size-tunable hexadecane-in-water emulsions
T2 - Effect of droplet size on destabilization of two-dimensional emulsions due to partial coalescence
AU - Abedi, Samira
AU - Suteria, Naureen S.
AU - Chen, Chau Chyun
AU - Vanapalli, Siva A.
N1 - Funding Information:
The authors thank the financial support of the Jack Maddox Foundation and National Science Foundation (CAREER: 1150836 ). We are grateful to Dr. Patrick Spicer and Dr. Swastika Bithi for useful discussions. Scott Hiemstra and Vince Wilde are gratefully acknowledged for assistance with assembly of the pressure control system.
Publisher Copyright:
© 2018
PY - 2019/1/1
Y1 - 2019/1/1
N2 - Hypothesis: Despite numerous studies, the mechanism of destabilization of oil-in-water emulsions during cooling-heating cycles is unclear due to indirect measurements and lack of direct control over the droplet size. It is hypothesized that emulsions with a smaller droplet size are more resistant to destabilization than emulsions containing larger droplets since the probability of initiating partial coalescence and forming large-scale aggregates is lower for small droplets. Experiments: Monodisperse hexadecane-in-water emulsions with controlled droplet sizes were produced using a microfluidic valve-based flow-focusing device and varying the system parameters. A unique approach was developed to create a two-dimensional (2D) array of droplets enabling visualization of the destabilization process due to temperature cycling. The influence of droplet size on partial coalescence and destabilization was investigated. Findings: In the 2D emulsion, destabilization proceeds through a combination of spontaneous coalescence events that yield small-scale structures followed by formation of large-scale structures by coalescence propagation. We find that emulsion destabilization increases with droplet size. Quantifying the frequency of n-body coalescence events reveals that in emulsions with small droplets coalescence propagation is hindered. Phenomena involving restructuring, growth and cross-linking of droplet aggregates are identified as the key features of the emulsion destabilization mechanism.
AB - Hypothesis: Despite numerous studies, the mechanism of destabilization of oil-in-water emulsions during cooling-heating cycles is unclear due to indirect measurements and lack of direct control over the droplet size. It is hypothesized that emulsions with a smaller droplet size are more resistant to destabilization than emulsions containing larger droplets since the probability of initiating partial coalescence and forming large-scale aggregates is lower for small droplets. Experiments: Monodisperse hexadecane-in-water emulsions with controlled droplet sizes were produced using a microfluidic valve-based flow-focusing device and varying the system parameters. A unique approach was developed to create a two-dimensional (2D) array of droplets enabling visualization of the destabilization process due to temperature cycling. The influence of droplet size on partial coalescence and destabilization was investigated. Findings: In the 2D emulsion, destabilization proceeds through a combination of spontaneous coalescence events that yield small-scale structures followed by formation of large-scale structures by coalescence propagation. We find that emulsion destabilization increases with droplet size. Quantifying the frequency of n-body coalescence events reveals that in emulsions with small droplets coalescence propagation is hindered. Phenomena involving restructuring, growth and cross-linking of droplet aggregates are identified as the key features of the emulsion destabilization mechanism.
KW - Microfluidics
KW - Monodisperse oil-in-water emulsions
KW - Multi-body coalescence
KW - Partial coalescence
KW - Valve-based flow-focusing device
UR - http://www.scopus.com/inward/record.url?scp=85051964271&partnerID=8YFLogxK
U2 - 10.1016/j.jcis.2018.08.045
DO - 10.1016/j.jcis.2018.08.045
M3 - Article
C2 - 30145441
AN - SCOPUS:85051964271
VL - 533
SP - 59
EP - 70
JO - Journal of Colloid and Interface Science
JF - Journal of Colloid and Interface Science
SN - 0021-9797
ER -