Three-dimensional fluid interface manipulation with printed structures for applications in materials, chemistry, and biomedical engineering

Fluid interfaces, including gas-liquid and liquid-liquid interfaces, are ubiquitous in nature and widely used in industrial applications. Many fundamental physical and chemical processes, such as evaporation, diffusion, adsorption, reaction, instability, and acoustic resonance, occur at the fluid interfaces, which form the pivot of chemistry, physics, biology, and material science. Engineering the fluid interface in a flexible manner can be very attractive for interfacial process research and technological renovations. To control fluid interface, numerous fluid manipulation methods have been developed. However, they still face great challenges in precise 3D fluid manipulation, including 1. lack of general methods to create structured 3D fluid interfaces. 2. the diversity of dynamic manipulation of 3D fluid interfaces is limited. 3. reversible liquid capture and release of capillary structures are still unattainable. 4. programmable 3D liquid patterning remains challenging. To address challenges 1 and 2, the magnetic-actuated “capillary container” composed of steel microbeads and a solid frame is proposed for the 3D fluid interface creation and dynamic manipulation. By wettability modification, 3D fluid interfaces with predesigned sizes and geometries can be constructed in air, water, and oils. Multiple motion modes were realized via adjusting the container’s structure and magnetic field. It is applicable to various fluids for applications in selective fluid collection and chemical reaction manipulations. Besides, the container can do liquid packaging via interfacial gelation for 3D membrane fabrication and controlled drug release. This versatile “capillary container” will contribute to diverse applications involving fluid sampling, transport, mixing, release, storage, and packaging. To overcome challenges 3 and 4, we present “switchable capillary and drainage containers” consisting of connected frames for 3D programmable liquid manipulation. The single-rod connected capillary containers can capture liquids, while the double-rod connected drainage containers release liquids. Reversible liquid capture and release are achieved by establishing or breaking the liquid continuity between the containers. Using predefined frame connections allows programmable 3D liquid patterning. In addition, the containers enable multifarious interfacial applications including reversible capillary sampling and release, high-flow evaporative humidifiers, and efficient CO2 capture. In conclusion, the proposed printed structure-based fluid manipulation methods will open broad applications in materials, chemistry, and biomedical engineering