Queen Mary University of London: â€œThe capsules, which have a diameter of two micrometers (about the size of a bacterium), are built by wrapping strands of a metabolism-resistant material around spherical particles, which are then dissolved in acid, leaving behind an empty container. To fill the capsules, the scientists heat them in a solution that contains the desired drug compound. This makes them shrink and traps some of the solution and compound inside. The loaded capsules are introduced into live cells by a technique known as electroporation – a tiny electric shock – which makes the cell walls permeable for micrometer-sized particles. The cells are unharmed by this treatment and retain the capsules.â€ â€“ The article refers to the capsules as â€œmicro shuttlesâ€ and states that the release of medication could also be controlled â€œby a biological trigger like a drop in blood sugar levels, or activated manually with a pulse of light.â€ – I worked on something similar as an undergrad. We applied various currents to polyaniline, forcing the polymer to take up and hold certain molecules. Reversing the current resulted in the polyaniline dropping the substance. Crazy technology! It makes me want to get into R&D.