Geckos and many other animals have heads that are too small to triangulate the location of noises the way humans do: with widely spaced ears. Instead, they have a tiny tunnel through their heads that measures the way incoming sound waves bounce around to figure out which direction they came from.
A similar system for detecting the angle of incoming light was developed that could let tiny cameras detect where light is coming from but without the bulk of a large lens, which is the typical way to determine the direction of light. These tiny detectors could record characteristics of light such as color, polarity, and angle of light. More detailed light detection could support advances in lens-less cameras, augmented reality, and robotic vision, which is important for autonomous cars.
If a sound isn’t coming from directly over a gecko’s head, one eardrum essentially steals some of the sound wave energy that would otherwise tunnel through to the other. This inference helps the gecko understand where a sound is coming from. This structure was mimicked in the photodetector by having two silicon nanowires — each about 100 nanometers in diameter — lined up next to each other like the gecko’s eardrums. They are positioned so closely that when a light wave comes in at an angle, the wire closest to the light source interferes with the waves, hitting its neighbor and basically casting a shadow. The first wire to detect the light would then send the strongest current. By comparing the current in both wires, the researchers can map the angle of incoming light waves.