A butterfly’s unusual way of drinking has inspired scientists to develop a tiny, low-cost device that can collect viruses, pollutants and other airborne threats without using a pump, battery or electricity.
Researchers at the Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences developed the technology as a possible alternative to conventional air-sampling equipment, which can be expensive, bulky and energy-intensive.
The new system, called Film-Rupture Actuated Capillary Enrichment, or FACE, can cost as little as $0.12 per disposable unit. The research was published in the Proceedings of the National Academy of Sciences.
The idea began with a question about butterflies.
Butterflies normally drink nectar through a long feeding tube called a proboscis. Scientists used X-ray imaging to examine how liquid moves through this structure and discovered a clever process that requires almost no energy.
When a butterfly’s proboscis is coiled, a thin film of liquid can form across its center. As this film becomes thinner, it eventually breaks. The surface energy stored in the film is suddenly released, pushing the remaining liquid rapidly into the feeding tube.
The entire process happens within milliseconds. No muscular pumping is required. Instead, the butterfly takes advantage of surface tension, the same basic physical force that allows water droplets to hold their shape.
The researchers wondered whether they could use the same principle to build a mechanical device that moves liquid without a pump.
Using inexpensive 3D printing, they created a device roughly the size of a coin. It contains a ring-shaped liquid film connected to tiny channels that imitate the butterfly’s feeding system.
When exposed to air, the liquid film acts like a microscopic sticky net. It can capture many types of airborne material, including pollutant gases, pesticide particles and tiny droplets containing viruses.
Once sampling is finished, a test strip is brought into contact with the device, causing the liquid film to break. The energy released by the rupture pushes the collected liquid through the tiny channels and directly toward the detection area.
Because the system uses energy already stored in the liquid surface, it needs no battery, motor or external power source.
Tests suggest that the technology could work in several real-world settings. The sampler continued functioning even in strong airflow, raising the possibility of attaching it to agricultural drones. Farmers could potentially use such devices to measure airborne pesticide residues over fields and assess exposure risks.
The system could also help monitor respiratory diseases. Because FACE is small and lightweight, it can be placed close to a person’s mouth and nose to capture exhaled droplets before they spread and become diluted in the surrounding air.
In experiments looking for a protein from SARS-CoV-2, the virus responsible for COVID-19, FACE achieved detection sensitivity 100 times greater than conventional pump-based aerosol samplers.
Part of this improvement comes from the device’s simplicity. Traditional air samplers may lose some of their collected material as samples travel through tubes or undergo recovery and dilution. FACE combines collection, concentration and delivery to a test area in one small system, reducing those losses.
The researchers believe the technology could eventually be useful for disease screening, pollution monitoring, agricultural safety and public health surveillance.
Its extremely low cost and lack of electricity requirements could make it especially valuable in remote areas and communities with limited resources.
In this case, inspiration from one of nature’s smallest drinking systems may lead to a surprisingly powerful new way to monitor the air around us.
