Fluidic delivery of homogeneous solutions through carbon tube bundles

Abstract

A wide array of technological applications requires localized high-rate delivery of dissolvedcompounds (in particular, biological ones), which can be achieved by forcing the solutionsor suspensions of such compounds through nano or microtubes and their bundledassemblies. Using a water-soluble compound, the fluorescent dye Rhodamine 610 chloride,frequently used as a model drug release compound, it is shown that deposit buildup on theinner walls of the delivery channels and its adverse consequences pose a severechallenge to implementing pressure-driven long-term fluidic delivery through nano andmicrocapillaries, even in the case of such homogeneous solutions. Pressure-drivendelivery (3–6 bar) of homogeneous dye solutions through macroscopically-long (∼1 cm) carbon nano and microtubes with inner diameters in the range 100 nm–1 µm and their bundled parallel assemblies is studied experimentally and theoretically. It isshown that the flow delivery gradually shifts from fast convection-dominated(unobstructed) to slow jammed convection, and ultimately to diffusion-limited transportthrough a porous deposit. The jamming/clogging phenomena appear to be rathergeneric: they were observed in a wide concentration range for two fluorescentdyes in carbon nano and microtubes, as well as in comparable transparent glassmicrocapillaries. The aim of the present work is to study the physics of jamming, ratherthan the chemical reasons for the affinity of dye molecules to the tube walls.