Biomimetic air purification with liquid-gating topological gradient microfluidics

Particle capture is vital for air purification in environmental protection, regional climate regulation and public health. In particular, filters operating with gas–liquid interfaces can provide efficient particle absorption and removal while serving in a maintenance-free manner. Here a liquid-gating topological gradient microfluidics (LGTGM) device is developed for air purification inspired by the liquid-assisted filtration mechanism of the human respiratory system. The LGTGM device is based on the continuous generation of microbubbles from a supplied gas flow. Due to the large specific interfacial surface area, together with tailored wettability in the device, particulate pollutants in the microbubbles preferentially transfer across the gas–liquid interface and enter a collection liquid. Benefiting from the fine regulation of bubble generation dynamics, multiple LGTGM devices can be combined in series or parallel to achieve efficient air purification as well as high-throughput processing. Moreover, the application potential of LGTGM is demonstrated for smoke filtration, disease prevention and visual detection. This study develops a liquid-gating topological gradient microfluidics device that generates finely tuned microbubbles in a functional liquid in a high-throughput manner for air purification in different scenarios.