Paper Number
MM1 

Session
Microrheology and Microfluidics

Title
Multiple particle tracking microrheology of thermally gelling nanoemulsions

Presentation Date and Time
October 9, 2017 (Monday) 3:45

Track / Room
Track 6 / Aspen

Authors (Click on name to view author profile)

1. Cheng, Li-Chiun (Massachusetts Institute of Technology)
2. Hsiao, Lilian C. (North Carolina State University, Department of Chemical and Biomolecular Engineering)
3. Doyle, Patrick S. (Massachusetts Institute of Technology)

Author and Affiliation Lines (in printed abstract book)
Li-Chiun Cheng¹, Lilian C. Hsiao², and Patrick S. Doyle^1
1Massachusetts Institute of Technology, Cambridge, MA; ²Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27606

Speaker / Presenter 
Cheng, Li-Chiun

Text of Abstract
We perform multiple particle tracking (MPT) on a thermally-gelling oil-in-water nanoemulsion system developed by our group [1]. We investigate the role of the colloidal probe size and surface chemistry on MPT in the nanoemulsion systems. As temperature increases, hydrophobic groups of PEG-based gelators (PEGDA) partition into oil/water interfaces and bridge droplets. This inter-colloidal attraction generates a wide variety of microstructures consisting of droplet-rich and droplet-poor phases [2]. By tailoring the MPT colloidal probe surface chemistry, we can control the residence of probes in each domain, thus allowing us to independently probe each phase. Our results show stark differences in probe dynamics in each domain. For certain conditions, the mean squared displacement (MSD) can differ by nearly five orders of magnitude for the same probe size but different surface chemistry. Some probe surface chemistries result in “slippery” probes while others appear to tether the probe to the nanoemulsion gel. We also observe probe hopping between pores in the gel for “slippery” probes at certain conditions. Our approach allows for the unique ability to probe different regions of a colloidal gel and is useful for measuring local properties in these mesostructured hydrogels [3]. References: [1] Helgeson, M.E., Moran, S., An, H., and Doyle, P.S., "Mesoporous organohydrogels from thermogelling photocrosslinkable nanoemulsions", Nat. Mater., 11, 344-352, 2012. [2] Hsiao, L.C. and Doyle, P.S.. "Sequential phase transitions in thermoresponsive nanoemulsions," Soft Matter, 11, 8426-8431, 2015. [3] Hsiao, L.C., Badruddoza, A.Z.M., Cheng, L.-C., and Doyle, P.S. "3D Printing of Self-Assembling Thermoresponsive Nanoemulsions into Hierarchical Mesostructured Hydrogels," Soft Matter, 13, 921-929, 2017.