Microgravity/microscale double-helical fluid containment

Abstract

Double-helical containment is a novel approach to open containment in microgravity (or at microscale). In contrast to axisymmetric containers, there is no length restriction on properly designed double-helical containers. Use of a double helix permits drainage to zero volume, an uncommon feature in microgravity; near-complete drainage is a key feature for any practically useful container. The fact that double-helical containers are open and tubular makes possible a broad range of applications that rely on accessible fluids.The double-helical fluid containment and the stability of such volumes are examined in detail. Helical supports permit filamentary containers of infinite extent, but only doublehelical containers are stable down to zero volume. The base case of symmetric supports (separation angle 1808) is considered in terms of symmetric volumes as well as asymmetric helicatenoid volumes. The distinct symmetric and asymmetric cases are then related by perturbing the angle of separation between the supports. The helicatenoid volumes may combine to form a dual helicatenoid volume. The dual helicatenoid is interesting in that it permits multiphase tube-like geometries.Double-helical behaviours such as drainability are found to vanish at a critical separation angle 246.488. With larger separation angles, double-helical containers behave like single-helical containers (3608), due to the dominance of the longer-span interface. A second shift in behaviour occurs at the limit angle 209.128, where the regions of stability including the cylinder and the helicatenoids become more connected. The common structures of DNA appear to coincide with the limiting geometry at 209.128. The most robust double-helical containers are therefore those with separation angles between approximately 2108 and 2408. Experimental results roughly verify the volume maximum for near-symmetry, and more importantly verify stability to zero volume.

Stability of Constrained Capillary Surfaces

“…DNA structure motivates the study of the helicoid to catenoid (H = 0) transition, tested using soap films on a wire frame (Boudaoud et al 1999). May & Lowry (2008) obtained the stability limits of volumes supported by dual helical boundaries, extending the work of Lowry & Thiessen (2007).…”

Dynamin's helical geometry does not destabilize membranes during fission

“…At low pitch, we indeed find that the solutions are CMC surfaces, agreeing with the results in Reference [], we call this the CMC region. When J s = 0, these surfaces interpolate isometrically between the catenoid and the helicoid, and are known by various names, including “heltocat” and “helicatenoid” . In every case with RJ s < 1, the surface exhibits a waist, resembling a helicoidally symmetric version of the catenoid.…”

“…When J s = 0, these surfaces interpolate isometrically between the catenoid and the helicoid, and are known by various names, including "heltocat" and "helicatenoid". 50,51 In every case with RJ s < 1, the surface exhibits a waist, resembling a helicoidally symmetric version of the catenoid. When RJ s = 1, the membrane forms a cylinder regardless of pitch.…”

Stability of constrained cylindrical interfaces and the torus lift of Plateau–Rayleigh

“…Their static stability analyses of the circular-arc cross-section base-state recover results of the previous studies and also treat some new substrate geometries. May & Lowry (2008) propose helical and double-helical wire constraints (pinning locus) to support liquid columns and calculate the static stability of resulting interfaces, which may or may not be nearly cylindrical. Despite the variety of these base states, the stability of the toroidal base state has not been considered before, as far as we are aware.…”