Light-triggered generation of multifunctional gas-filled capsules on-demand

A combination of a microfluidic technique and laser-triggered reactions has been developed to fabricate functional gas-filled capsules (GFCs) on-demand with applications such as a pressure sensor. This method involves (i) the generation of monodispersed alginate microcapsules containing ammonium bicarbonate (AB) as gas resource and gold nanorods as a heating resource, in a microfluidic device; and (ii) the near-infrared light-triggered generation of gases from the AB-containing microcapsules and simultaneous encapsulation of the gases in an alginate shell to produce GFCs. Various functional substances such as dyes, quantum dots, and magnetic nanoparticles can be introduced into the shell of the GFCs to impart the system with multifunctionality. We further demonstrated the use of the GFCs as pressure sensors capable of sensing the variation in the pressure of environment.