Last week Daedalus outlined his new ‘microdermic needle’ injection technology. A giant multilayered carbon nanotube, a micrometre across and coated with slippery graphite fluoride, is drawn into the body by ultrasonic pulses sent down it. It noses its way harmlessly between the cells, even those of bone, and is steered under imaging control to the injection site.

Daedalus now muses that, thanks to its insulating coating of graphite fluoride, his new needle is an ideal biological electrode. It could sense an electrical potential at its tip, and relay electrical signals back down again.

The obvious target organ is the brain. Unlike electroconvulsive therapy, microdermic therapy would allow precise intervention. Far too fine to hurt or even be noticed, a microdermic needle could be inserted into the skull of the conscious patient, and steered around his brain. Like a precision electroencephalograph, it would detect the electrical activity of the cells it encountered. Pulses could then be sent down it to reinforce or modify their action. Sudden memories, ideas, or motives might grip the patient, revealing their exact site in the brain. His mentality could be mapped in detail and its troubles precisely located.

The same needle could then be used for therapy. A drug — say a neurotransmitter or an antipsychotic — could be passed down it to normalize the local brain cells. Alternatively, a pattern of electrical pulses might be devised for the same purpose. Inert, painless, undetectable, the needle could be left in place indefinitely, for future (or even maintained ‘depot’) corrective action. Manias, obsessions and delusions could be erased, tics and seizures switched off. Psychiatry would become an exact science at last.

The technology might even be developed into quite a general man-machine interface. Inserted into a nerve, a microdermic needle could read the traffic in that nerve, and launch impulses into it. A computer attached to the needle could learn to command that nerve. The first applications would be prosthetic — restoring sensation and action to victims of paralysis, or sensory and functional disorders. But a mass of needles densely distributed through the nervous system, all connected to a true back-pack ‘personal computer’, would create the very first cyborg robot: a computer seeing through human eyes and controlling a human body.