Compliant polymer origami bellows in cryogenics

Abstract

Mechanical applications for polymers at cryogenic temperatures are extremely limited due to decreased atomic mobility and ductility, resulting from glass transitions above the cryogenic regime (<120 K). As such, polymeric materials are known for cracking and low fatigue life. Crumpling polymer films has been historically researched as a mechanism to bypass this brittleness for mechanical actuation, but characterization of the fatigue life of polymer films to cyclical crumpling at 77 K determined that films shatter after a few cycles. To improve upon this performance, we fabricated thin-film origami bellows with Yoshimura and Kresling geometries to primarily restrict strain to below the elastic limit. We found the resulting bellows survived 100 full compression and extension cycles at 77 K by submerging the bellows in liquid nitrogen during testing: no tears or pinholes were detected in the bellows following a dye penetrant procedure. These results indicate that restricting the strain modes in thin-film polymers via origami structures could be applicable to a range of cryogenic technologies useful for liquid storage bladders, expandable seals, positive displacement fluid pumps, and flexible electronics.