Desert horned lizards that drink captured water from their skin inspire water-harvesting system

A bioinspired system for harvesting water from soil offers a sustainable solution to water scarcity in arid environments, according to the Seoul National University and Daegu Gyeongbuk Institute of Science and Technology researchers who developed it.

Desert horned lizards (Phrynosoma platyrhinos) have unique skin microchannels to enable water collection in the dry climate of North America where they live. Exactly how they drink the collected water, however, has ‘long remained elusive’, according to the research team.

After closely observing 12 lizards, the researchers have revealed that these lizards use ‘unique’ rhythmic jaw movements to squeeze and transport water from their skin – a process that they have now translated into a multifunctional water system.

The lizards use their skin to harvest water from raindrops and moist or damp spots of soil through capillary action in the arid deserts of North America. The researchers showed that slow opening of the lizards’ jaws then allows the initial drawing of this water into the corners of their mouths between their lower and upper jaws. Upon rapid closing of the jaws, the skin at the corner folds inward, squeezing the water into the lizards’ mouths.

Through hydrodynamic modelling, the researchers found this motion facilitates efficient water intake. They applied these insights to an artificial system which they say ‘holds promise’ for regions where water is scarce but could be gathered instead from damp soil.

In tests, the ‘lizard-jaw mimicking device’ made use of porous media similar to the microchannels on the lizards’ skin to harvest water from a pile of glass beads within a polymer reservoir that simulates soil. It also makes use of an asymmetric cyclic motion seen in the jaw movements of horned lizards to pump the gathered water, applied to two glass plates – one fixed and one hinged.

‘Much of the world’s untapped water isn’t in rivers or reservoirs but locked in damp, often contaminated soil that’s difficult to use – and the desert horned lizard showed us it can be drawn out through simple, rhythmic capillary action rather than high pressure or large energy inputs,’ explains Ho-Young Kim at Seoul National University. ‘Because our system collects and purifies in a single low-power step and scales by running many small units in parallel, it’s well suited to off-grid, resource-limited settings, from remote arid communities to disaster relief. We see it less as a single device than as a flexible, nature-inspired template for sustainable water harvesting where conventional infrastructure can’t reach.’

A Nafion ion-exchange material was also integrated into the pores of the spongey material to remove harmful contaminants like heavy metals and purify the water. After saturation, the Nafion coating can be regenerated by soaking it in acidic solution for around 30 minutes, restoring its performance. The research team notes that even in the presence of a ‘complex mixture of cations’ found in damp soil, the system remains capable of removing heavy metals and may also find application in the purification of brackish water.