Fig. 5: Controllable liquid capsule for on-demand cargo delivery.

a Schematic diagram showing a ferrofluid droplet transforming a traditional pill into an active drug delivery system. b The active construction, controlled locomotion and on-demand release of a liquid capsule in an ex vivo animal stomach. c Schematic diagram of a liquid capsule that ejects its internal cargo on demand by applying a magnetic field. d Liquid capsules maneuver in various motion modes while carrying the liquid or solid cargo and release on demand. (i) Liquid cargo delivery. (ii) Solid cargo delivery and mixing. (iii) Two liquid capsules are actuated together to deliver the liquid cargo and fuse. The substrate is made of hydrogel. e The liquid capsule shuttles back and forth in the channel, which is made of hydrogel, for 40 min before ejecting the liquid cargo. f The liquid capsule moves in a bile duct phantom made of soft gel, inside whose narrow branches are in stretching mode and release the liquid cargo on demand. g Ultrasound Doppler-guided locomotion of the liquid capsule in an ex vivo animal bile duct. Color bar represents the Doppler signal. Scale bars, 2 mm.