Cell retention device
A cell retention device includes a structured support with a plurality of circumferentially distributed ribs to retain the active filtering surface of a flexible, porous membrane filter medium. The filter medium surrounds the support in contact with the peaks of the ribs, thereby forming axial voids between the rib peaks. This arrangement imparts sufficient structural support over small regions of the filter medium to facilitate its use in a circular (or other rounded) configuration while providing sufficient channel volume to support high throughput of fluid sparse of cells.
1 . A filter comprising:
an elongated element having a plurality of longitudinal segments, each having a plurality of axial ribs circumferentially distributed around an exterior portion thereof, the axial ribs having radial peaks and radial recessions therebetween, the elongated element being substantially nonporous, and adjacent longitudinal segments of the plurality of longitudinal segments are sealably fitted together in a stacked sequence;
a membrane filter medium wrapped as a planar sheet around the exterior portion of the elongated element and in contact with the elongated element at only the radial peaks of the axial ribs, thereby forming a plurality of axial voids between the radial recessions and the membrane filter medium;
a central channel extending axially through at least a portion of the elongated element and terminating in an outlet; and
at least one radial channel fluidically coupling the axial voids to the central channel, whereby negative pressure at the outlet propagates through the axial voids to the membrane filter medium,
wherein the plurality of axial ribs is interrupted by one or more annular regions between adjacent longitudinal segments of the plurality of longitudinal segments, the one or more annular regions radially recessed relative to the radial recessions of the plurality of axial ribs.
2 . The filter of claim 1 , wherein the at least one radial channel has a first end opening into the central channel and a second end opening into one of the one or more annular regions radially recessed relative to the ribs.
3 . The filter of claim 2 , wherein the annular region is unribbed.
4 . The filter of claim 2 , wherein the annular region has a plurality of circumferentially distributed radial channels therethrough.
5 . The filter of claim 2 , wherein the elongated element includes a plurality of unribbed annular regions each having a plurality of circumferentially distributed radial channel therethrough.
6 . The filter of claim 1 , wherein the filter medium is cellulose ester.
7 . The filter of claim 1 , wherein the filter medium is polyethersulfone.
8 . The filter of claim 1 , wherein the filter medium is cellulose acetate.
9 . The filter of claim 1 , wherein the filter medium is polyvinylidene fluoride.
10 . The filter of claim 1 , wherein the filter medium is polycarbonate.
11 . The filter of claim 1 , wherein the elongated element has a substantially circular cross-section.
12 . The filter of claim 1 , wherein the radial peaks each have (i) a radial height relative to the radial recessions and (b) a circumferential width, the radial height being approximately equal to the circumferential width.
13 . The filter of claim 1 , wherein the central channel has first diameter and the elongated element with the membrane filter medium wrapped therearound has a second diameter, a ratio of the first diameter to the second diameter ranging from 0.1 to 0.95.
14 . The filter of claim 13 , wherein the ratio of the first diameter to the second diameter is 0.75.
15 . The filter of claim 1 , wherein the elongated element has a length and the elongated element with the membrane filter medium wrapped therearound has a diameter, a ratio of the element length to the diameter being approximately 3.0.