Tubesheet and method for making and using the same

A tubesheet, modules incorporating tubesheets and methods for making and using the same. In one embodiment the invention includes a tubesheet comprising: i) a plurality of aligned semi-permeable hollow fiber membranes each comprising a cylindrical porous structure surrounding a lumen and extending between a first and second end and further comprising a first segment located adjacent the first end and a second segment located adjacent to the second end and ii) a block of potting material including an interfacial surface. The first segment of the hollow fiber membrane is embedded within the block of potting material and the second segment extends from the interfacial surface of the block. The tubesheet further comprises a penetrating extension of potting material within the porous structure of the second segment of the hollow fiber membrane that extends along a length from the interfacial surface of the block to a distal end.