Generating oil-in-water Pickering emulsions in PDMS to synthesize plasmonic mechanochromic microcapsules*

Oil-in-water (o/w) Pickering emulsions stabilized by gold nanoparticles (AuNPs) were synthesized using polydimethylsiloxane (PDMS) chips. These emulsions serve as the basis of a mechanochromic microcapsule (MC) with AuNPs at their surface. Exterior stimuli such as mechanical strain or pH induce a conformational change in the MCs, and thus a change in plasmonic resonance exhibited by the AuNPs. Emulsification by ultrasonication having been proven successful ^[1][2], we plan to synthesize MCs via microfluidics as it allows relative ease of control of the process and in situ observation of emulsification. PDMS, widely used in microfluidics, is not considered suitable for o/w emulsification. Here we present microfluidic experiments carried out in search of optimal conditions for stable o/w Pickering emulsions in PDMS.

[1] Burel et al., Plasmonic Based Mechanochromic Microcapsules as Strain Sensors. Small, 2017.
[2] Burel et al., Plasmonic Elastic Capsules as Colorimetric Reversible pH Microsensors. Small, 2020.