(525b) In Situ Mechanical Testing of Bijel Fibers

Bicontinuous interfacially jammed emulsions (bijels) are a new class of soft materials [1] with promising applications in various areas ranging from healthcare, food, energy and reaction engineering due to their unique structural, mechanical and transport properties. We recently presented a new method to prepare bijels via solvent transfer-induced phase separation (STRIPS), which enables continuous fabrication of hierarchically structured bijel fibers using a microfluidic platform [2]. Understanding the mechanical properties of these bijel fibers is crucial for their implementation in new technologies. Here, we introduce a novel microfluidic in situ technique to measure the yield strength of bijel fibers, and potentially the mechanics of other fibrous materials. The yield strength of bijel fibers depends on the various factors such as the age of the bijel material, the nanoparticle concentration and the strength of particle-particle attraction. We show that such fibers with controlled aspect ratios can be fabricated by varying the flow rates in a co-axial microfluidic device and explain the formation process with a simple force-balance model. These findings broaden the potential for the use of STRIPS bijels in applications with different mechanical demands. Moreover, our in situ mechanical testing method could potentially enable the mechanical characterization of various soft fibrous materials such as hydrogels and protein complexes.

[1] Herzig, E. M., et al. (2007). Nature materials, 6(12), 966-971.

[2] Haase, M. F., Stebe, K. J., & Lee, D. (2015). Advanced Materials, 27(44), 7065-7071.