Fluidic delivery of homogeneous solutions through carbon tube bundles

Abstract

A wide array of technological applications requires localized high-rate delivery of dissolved compounds (in particular, biological ones), which can be achieved by forcing the solutions or suspensions of such compounds through nano or microtubes and their bundled assemblies. 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 the inner walls of the delivery channels and its adverse consequences pose a severe challenge to implementing pressure-driven long-term fluidic delivery through nano and microcapillaries, even in the case of such homogeneous solutions. Pressure-driven delivery (3-6 bar) of homogeneous dye solutions through macroscopically-long (approximately 1 cm) carbon nano and microtubes with inner diameters in the range 100 nm-1 microm and their bundled parallel assemblies is studied experimentally and theoretically. It is shown that the flow delivery gradually shifts from fast convection-dominated (unobstructed) to slow jammed convection, and ultimately to diffusion-limited transport through a porous deposit. The jamming/clogging phenomena appear to be rather generic: they were observed in a wide concentration range for two fluorescent dyes in carbon nano and microtubes, as well as in comparable transparent glass microcapillaries. The aim of the present work is to study the physics of jamming, rather than the chemical reasons for the affinity of dye molecules to the tube walls.

Nanogel formation of polymer solutions flowing through porous media

“…After this initial interaction of the PAA molecules with sand or with ballotini particles, which have a chemical composition similar to sand with a high amount of SiO 2 , a jamming phenomenon occurs gradually which is enhanced at very large deformation rates. A jamming clogging effect was also observed by Srikar et al 24 in homogeneous solutions of Rhodamine 610 chloride flowing through carbon micro and nanotube bundles. In our case, the gelation process is the outcome of a sequence of events, acting like a snowball effect: after the initial adsorption of the PAA molecules on the SiO 2 surfaces, the jamming phenomenon of the polymer chains occurs by a simultaneous combination of extreme shear (relatively high flow rates) and elongational conditions (narrow interstitial spacing), combined with flow induced initial aggregation of the polymer chains that contribute to decrease the effective pore size.…”

Nano-encapsulated smart tunable phase change materials

“…2 shows, the inner surface of these CNTs is rather rough, which probably makes wax deposition non-uniform and maybe even unstable according to the mechanism described in ref. 13.…”

“…A careful examination of the images in Fig.1reveals that some ordered striations (marked by arrows; several of them highlighted in Fig.1B and C) are visible in the intercalated deposits inside the CNTs. As Fig.2shows, the inner surface of these CNTs is rather rough, which probably makes wax deposition non-uniform and maybe even unstable according to the mechanism described in ref 13…”

Coaxial electrospinning and emulsion electrospinning of core–shell fibers

“…Then, pressure driven‐flows inside co‐electrospun and carbonized micro‐ and nanotubes were demonstrated 70. 71 In the latter two works, at the co‐electrospinning stage, core–shell fibers were collected as parallel bundles of about 40 000 fibers using the method of the electrostatic lens (a sharp vertical grounded wheel) 2. 72, 73 After carbonization, these bundles were converted into bundles of parallel carbon nanotubes (Fig.…”

“…Such issues as clogging of co‐electrospun carbon nanotubes, which are relevant for long‐term drug delivery devices, were addressed in Reference 71.…”