Partially miscible droplet microfluidics to enhance interfacial adsorption of hydrophilic nanoparticles for colloidosome synthesis

Colloidosomes are spherical shells composed of closed-packed nanoparticles, which can be prepared through the self-assembly of nanoparticles at the interphase of two immiscible liquids. However, the method leads to colloidosomes of various sizes and limited synthesis due to charge repulsion and nanoparticle wettability. Herein, a microfluidic droplet device and partially miscible liquids are integrated for colloidosome synthesis. Dissolving liquids within droplets enables hydrophilic nanoparticles to close packing at the liquid interface to form colloidosomes. Moreover, the microfluidic droplet system achieved colloidosomes within a narrow and specific range of sizes. The close-packing of nanoparticles is proved by modifying colloidosomes into probes in signalenhanced lateral flow assays (LFAs). Due to the plasmon resonance effect, the testing lines are black, demonstrating the close packing of nanoparticles and their signal enhancement property compared to traditional LFAs. Accordingly, this approach is a potential bacterial detection platform with a detection time of 10 min, higher sensitivity, and specificity. Moreover, since colloidosomes are hollow spheres, they are capable of drug cargo with an encapsulation rate of 99.76 %. With this proposed partially miscible fluid-based droplet microfluidic system, colloidosomes can be fabricated with versatile properties, extending their application to advanced material fabrication, drug encapsulation, and biosensing.

Automated summary

This article introduces a new technique for the synthesis of colloidosomes using a microfluidic droplet device and partially miscible liquids. By dissolving liquids within droplets, hydrophilic nanoparticles can be close-packed at the liquid interface to form colloidosomes. This method also enables colloidosomes to be synthesized within a narrow range of sizes. The close-packing of nanoparticles is confirmed by modifying colloidosomes into signal-enhanced lateral flow assays, which demonstrates their potential application in bacterial detection platforms, drug encapsulation, and biosensing.