Tiny antennas make brain implants a little more possible.

Nature explores the possibilities of, in not so many words, putting electronic receivers in our brains:

Metal antennas that send and receive TV signals and radio waves could soon be replaced by tiny films up to one hundred times smaller, scientists say. Among the possible benefits are smaller smartphones and wearable technology, and miniaturized implantable devices to stimulate brain cells.

The prototype antennas work by coupling acoustic waves — vibrations in a material — with electromagnetic waves. They employ a thin piezoelectric membrane, which vibrates when subjected to an electric current. This vibration in turn stretches and compresses an attached film which contains magnetic particles. That action creates an oscillating magnetic field, and in turn an electromagnetic wave. The process occurs in reverse to pick up radio waves: incoming radiation sets up an oscillating magnetic field in the film, which induces vibrations in the attached membrane, whose changing shape generates the electric signal.

The antennas might be used on chips in the brain, [Northeastern University engineer Nian Xiang] Sun says. Biomedical researchers already use transcranial magnetic stimulation — in which a magnetic coil positioned outside the head induces electrical currents inside the brain — to treat depression and migraine; the technique is also being researched to treat learning disorders. But directing the electromagnetic waves from the coil is tricky. An implantable, controllable chip that receives and emits electromagnetic radiation could stimulate neurons more precisely, if its antenna could be shrunk.

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