Superhydrophobic "Aspirator": Toward Dispersion and Manipulation of Micro/Nanoliter Droplets.

of the tiny droplets dispersed from the commercial needle nozzle. Therefore, to solve this issue, a superhydrophobic system that possesses real-time switchable water adhesion can be utilized for the capture of tiny droplets with certain volumes, i.e., “sticky” surface for tiny droplet capture and the “nonsticky” surface for releasing the captured droplet. [ 6 ] In general, the water adhesion property of superhydrophobic materials can be controlled by utilizing electric and magnetic fi elds, changing temperature and pH value, etc. [ 7 ] However, most of those advanced techniques require complicated equipment and slowly respond to the external environments, which might not be suitable for the simultaneous and convenient manipulation of tiny droplets. Here, we report that the superhydrophobic mesh under specifi c negative air pressure supply, viz. a superhydrophobic “aspirator,” can quantitatively prepare and facilely manipulate the micro/nanoliter droplets. The continuous and tunable negative air pressure generated by a vacuum pump was incorporated into the backside of the superhydrophobic mesh, and therefore its front surface can generate a controllable adhesive force for the capture of tiny droplets ( Figure 1 a). This particular device provides a potential method for the dispersion and manipulation of micro/nanodroplet and can meet wide requirements in the fi eld of interface research, trace analysis, microfl uidics, etc. The superhydrophobic mesh was fabricated through a simple dip-coating process, i.e., the copper mesh with a pore diameter of ≈200 μm was immersed into a mixed solution containing polydimethylsiloxane and hydrophobic fumed silica. After solidifi cation of the coating, the superhydrophobic mesh was integrated into a vacuum system to construct the superhydrophobic “aspirator” (Figure 1 b and Figure S1, Supporting Information). The silica nanoparticlebased hydrophobic layer was selected due to its durable, water-repellency performance, and easy-to-prepare. [ 4a ] The processed superhydrophobic mesh has a contact angle of 151.8° ± 1.1° (Figure 1 c), and the observation of scanning electronic microscope illustrates the nanoscale roughness successfully fabricated on the mesh surface (Figure 1 d). Due to the addition of hydrophobic layer, the pore diameter was decreased from ≈200 to ≈150 μm. Inspired by the common aspirators, we displayed that the superhydrophobic “aspirator” can utilize a negative air pressure to generate droplet attraction. In the static analysis, the negative pressure on the droplet was balanced with the DOI: 10.1002/smll.201501023 Dispersions