Micro/nanofluidic transport by special fibers deposited by electrohydrodynamic direct-writing

Recently micro/nanofluidic transportation is important in many natural and engineering processes, such as water collection, fluid patterning and microfluidic chip. But the natural microstructures for fluid transportation are usually difficult to manufacture and adjust. Here we find that some fibers (the diameters < 10 μm) deposited by electrohydrodynamic direct-writing(EDW) can be directly used for micro/nanofluidic transportation due to the geometries of fibers. The liquid paraffin (its minimum width < 100 nm) can transport along the circular fiber because of the wedge microcavities formed by circular fiber and substrate. Ultrafast directional water transport (about 22 mm/s) has been achieved by oblique elliptic fiber array which has been placed at a distance of 300 μm above the substrate. Moreover, we found that the contact angles of the test liquids on the substrates and on the fiber materials also play a crucial role in this structure. So electrowetting has been used to change the contact angles of water on the substrate to fast switch (response time < 0.4 s) direction of water transport. We think electrohydrodynamic direct-writing the fibers with various geometries opens up new low-cost, high efficiency, fast and accurate pathways to realize fabric-based wearable microfluidic device.