Nature news article describes the system as follows: To make the one-inch London chip, the team etched a plan of the city centre on a glass slide. Fitting a flat lid over the top turned the streets into hollow, connected tubes. They filled these with helium gas, and inserted electrodes at key tourist hubs. When a voltage is applied between two points, electricity naturally runs through the streets along the shortest route from A to B - and the gas glows like a tiny neon strip light. The approach itself provides a novel visible analog computing approach for solving a wide class of maze searching problems based on the properties of lighting up of a glow discharge in a microfluidic chip. Application to voltage regulation In the mid-20th century, prior to the development of solid state components such as Zener diodes, voltage regulation in circuits was often accomplished with voltage-regulator tubes, which used glow discharge. See also Electric arc discharge Electric spark Electrical breakdown Electrostatic discharge Vacuum arc X-ray tube Fluorescent lamp, neon lamp, and plasma lamp List of plasma (physics) articles References Further reading First chapter of the article Secondary effects by P.F. Little. Electrical discharge in gases Gas discharge lamps Lighting Ion source Analytical chemistry