The starting point is a glass plate coated with cell-repellent material. The desired circuit pattern is scratched into this coating and then coated with a cell-friendly adhesive. Unable to gain purchase on most of the plate, the cells are forced to grow in the scratched areas.
The scratched paths are thin enough to force the neurons to grow along them in one direction only, forming straight wire-like connections around the circuit.
Using this method the researchers built a device that acts like an AND logic gate, producing an output only when it receives two inputs.
A computer without COBOL and Fortran is like a piece of chocolate cake without ketchup and mustard.