Be sure to check out part 3 of this 5-part series: " 5 Uses for the Astonishing Power of 2D Materials ," and check back next week for part 5!

No matter how strong the spirit, the flesh is weak. Fragile. Mortal. Usually doesn't smell very good. Cursed with a decidedly unappealing combination of corpse-pale skin and dense, almost werewolfesque body hair - at least when it's my flesh.

DARPA, the Defense Advanced Research Projects Agency - the folks who brought you the foundations of the Internet, the MQ-1 Predator attack drone, and Metal Gear REX - recently performed a remarkable experiment. The subject was a 28-year-old man who'd lost his hand a decade prior. In its place, a mechanical hand was attached. Sensors connected to the artificial limb were implanted in the motor cortex of his brain. There, they detect the electrical activity of firing nerve cells. When the patient thinks of moving his missing hand, the implants pick up the signal and send it to the artificial hand, which moves in accordance with the user's will like a real limb.

Meanwhile, mechanical sensors in the limb's fingers send their own signals back to another implant, this one an array of electrodes in the subject's somatosensory cortex - the main area of the brain responsible for the sense of touch. When the hand's sensors detect pressure, the electrodes stimulate the surrounding nerves to produce corresponding tactile sensations in the brain - replicating that sense of touch. This is not the first such experiment, but it is the most impressive to date. The volunteer was able to tell which of their individual fingers was being touched while blindfolded with almost perfect accuracy.

A machine has pressure applied to some torque sensors, and a conscious human mind feels it.

Attempts to send information directly between machines and organic brains date back to the 1960s. From crude origins, research into this area - whether by actually implanting devices into the brain or through less invasive means - has grown increasingly sophisticated.

There are many challenges still to overcome. Our understanding of the human nervous system is quite limited. The amount of information that can be transmitted across existing implants is very modest - a human brain and a computer using them to communicate is a bit like a pair of brilliant scientists trying to discuss the details of their research by blinking at each other in Morse code. And brains are a lot like people: They often react poorly to having bits of metal stuck into them. Luckily, progress is being made in all of these areas, and shows no sign of stopping.

This could be just the beginning. Brain-computer interfaces (BCI) could have incredibly far-reaching implications, not just for people with disabilities but for everyone. Medicine, work, entertainment, the legal system - all could be deeply affected as our ability to link mind and machine grows. It could even be used to go beyond just restoring normal human abilities to those who've lost them to enhance people beyond previous human limits - perhaps, someday, beyond what many people would even consider being human.

It would also revolutionize porn, but that goes without saying, since the first thing every new communication technology is used for is revolutionizing porn. Nonetheless, here are five other ways in which brain-computer interfaces will change the world - and us.