Creating direct interfaces between humans and machines isn't easy, because our bodies use more than just electricity to send signals. We also rely on ions and protons, and the same material that makes up the insides of squids and the outsides of crabs can be used to tap into these channels to control our cells directly.
Computers work by shuffling around electricity in the form of electrons. Our nervous system works in kind of the same way, with electricity, which is why we can use electric pulses to stimulate our muscles. To control more complex processes, like cell membrane channels, our bodies use ions and protons, which are trickier to control. Materials scientists at the University of Washington have taken a compound called chitosan, which can be found in squid backbones and crab shells, and used it to create a sort of biological transistor that can generate and channel proton currents to interface with biological systems.
Chitosan is ideal because it's easy to get, easy to mess with, and your body won't freak out if you've got some of it implanted into you. It absorbs water and forms a bunch of hydrogen bonds, allowing protons to jump from one bond to the next, analogous to how electronic circuits work. Researchers are hoping that this is the first step to creating a way for computers to sense biological activities in our bodies, and eventually, allow us to control specific functions inside our own cells. This may not mean an implantable button that you can push to fill your body with adrenaline to perform superhuman feats, but then again, it might mean that, too.