Forceless Sadowsky strips are spherical.

We showthat thin rectangular ribbons, defined as energy-minimizing configurations of the Sadowsky functional for narrowdevelopable elastic strips, have a propensity to form spherical shapes in the sense that forceless solutions lie on a sphere. This has implications for ribbonlike objects in (bio) polymer physics and nanoscience that cannot be described by the classical wormlike chain model. A wider class of functionals with this property is identified.