MIT researchers redesigned ordinary fog nets, changing the mesh and coating, to extract drinking water from air in some of Earth's driest regions

In Chile, the Atacama Desert is widely described as one of the driest places on Earth, with parts of it going years at a time with almost no rainfall. Yet the dense fog known as the camanchaca moves across Chile's arid coastal region daily, carrying fresh water that largely goes uncollected. Researchers at MIT found a simple way to harness this underused resource without developing complex technology. Instead, they innovated on existing mesh nets. By adjusting fiber diameter and the mesh coating, the engineers created a fog collector that captured far more water than existing designs.

How the MIT fog-harvesting mesh works

According to MIT News, engineers at MIT worked with researchers in Chile to create a mesh for fog collectors. They found that this new mesh can catch much more water than the nets people use around the world. The findings were published in the journal Langmuir under the title "Design of Permeable Fiber Network Structures for Fog Harvesting." The people who did this study are Kyoo-Chul Park, Shreerang Chhatre, Siddarth Srinivasan, Robert Cohen, and Gareth McKinley. The mesh design remains an important basis for fog-harvesting research today.


Why fog can provide water

Rainfall is not the only source of freshwater from the sky. For example, in coastal desert regions, fog often comes from the ocean rather than from rain. Plants, animals, and people in these areas have relied on fog for water for many years. MIT's team aimed to achieve this on a much larger scale. A simple mesh-net system is used to harvest water from fog in more than 17 countries. However, the major problem here is efficiency. Most nets use plastic with relatively large fibers.

What changing the mesh actually did

Three factors determine how much water a net can harvest: fiber diameter, spacing between fibers, and the fiber coating. The researchers at MIT investigated each of these factors. The team found that the best results came from stainless-steel fibers three to four times the diameter of a hair, spacing set at twice the fiber diameter, and a surface coating that removed water droplets quickly before the wind carried them away. The new mesh is considerably more efficient. While a traditional mesh net captures just 2% of the water contained in fog, the MIT mesh captured 10% or more, making it about five times more efficient. Several layers of this finer net can improve this yield even further.

Testing the idea on a hillside in Chile

A good lab result does not mean much until it is proven in field conditions. To do so, the MIT researchers worked with the Pontifical Catholic University in Santiago and tested the mesh on hilltops in a semi-arid region north of the city, not the Atacama itself, but a separate stretch of Chile's fog belt that sees little rainfall and is frequently blanketed by dense fog driven by the camanchaca winds. The site was chosen partly for its accessibility, offering researchers a practical proxy for the more remote and harsher conditions of the Atacama. The researchers conducted a one-year test of the new mesh in this area to determine how efficiently it would operate and how long it would last.

Fog collectors currently used in coastal Chile collect only a few liters of water per square meter of mesh per day. MIT researchers estimate that an improved mesh could yield up to 12 liters of water per square meter under the strong winds and dense fog typical of Chile's coast. Separately, researchers in Chile calculated that collecting just 4 percent of the fog's water content could be enough to meet the water needs of the country's four northernmost regions, which make up the Atacama Desert.

Why this still matters today

A water source that requires no energy can be valuable in places with few other options. These fog collection nets are not a substitute for pipelines and water treatment facilities. However, when a community lacks a nearby water source, a low-cost system that does not require electricity and needs little maintenance may be very helpful. As Gareth McKinley of MIT's Department of Mechanical Engineering says, nature did the hardest part already: it evaporated the water, desalinated it, and made droplets. Access to clean water remains a pressing global issue. According to the United Nations, over two billion people worldwide lack access to safe water resources, and about half of the world's population experiences an acute water shortage for at least part of the year.

The bottom line

A finer, more accurate mesh, along with a coating with the right chemical mixture, made the age-old concept several times more efficient. For communities already living alongside the camanchaca, that improvement could mean the difference between a trickle of water and a usable daily supply.