Physical maze solvers. All twelve prototypes implement 1961 Lee algorithm

TL;DR

This paper reviews twelve experimental maze solver prototypes that implement the Lee algorithm using various physical phenomena, comparing their methods, speed, costs, and durability.

Contribution

It provides a comprehensive overview of diverse physical maze solvers and analyzes how they approximate the Lee algorithm through different gradient-based methods.

Findings

All prototypes implement the Lee algorithm concept.

Various physical phenomena are used to trace paths, including electrical, chemical, and biological methods.

Prototypes differ in speed, cost, and durability of path visualization.

Abstract

We overview experimental laboratory prototypes of maze solvers. We speculate that all maze solvers implement Lee algorithm by first developing a gradient of values showing a distance from any site of the maze to the destination site and then tracing a path from a given source site to the destination site. All prototypes approximate a set of many-source-one-destination paths using resistance, chemical and temporal gradients. They trace a path from a given source site to the destination site using electrical current, fluidic, growth of slime mould, Marangoni flow, crawling of epithelial cells, excitation waves in chemical medium, propagating crystallisation patterns. Some of the prototypes visualise the path using a stream of dye, thermal camera or glow discharge; others require a computer to extract the path from time lapse images of the tracing. We discuss the prototypes in terms of speed, costs and durability of the path visualisation.