Core-shell droplet generation in an on-chip temperature gradient

We present a microfluidic device and associated heating/cooling setup for the generation of droplets stabilized by a lipid-crystalline shell. A conventional flow-focusing microfluidic droplet generator with 31 µm feature size was equipped with an on-chip resistive heater and placed on a microscope stage Peltier cooler in order to generate and isolate oil-in-water droplets enveloped by a crystalline shell of glycerol monostearate (GMS). A proof-of-concept protocol was developed for droplet generation over a temperature range between 60°C and 6°C, and GMS-coated droplets with a size between 13 and 49 µm were collected.

Practical application: Stabilized oil droplets of controlled size with a long shelf life and high thermal stability are of importance in various food applications. Improved emulsion stabilization prolongs retention of food quality. The GMS shell can efficiently preserve and protect sensitive cargo, such as flavors and nutrients. Reinforced droplets can also act as fat mimetics in low-fat or vegan formulations, help tailor mouthfeel, and enhance creaminess as well as spreadability. Given the size range of the particles produced, applications as microreactors for enzymatic reactions, which could enable new textures or flavors via micro-scale processing, are conceivable.