On the chirality of paper

On a macroscopic level, a paper sheet has a fiber structure similar to the chains of a molecular chiral membrane. The continuum model of membranes based on chiral elasticity can be applied to calculate the spontaneous curl observed in paper sheets. Twist of the paper sheet is shown to occur in the presence of a tilt relative to the sheet geometry of the constituent cellulose fibers. The dependence of the twist angle on the width of the sheet, on external mechanical fields and on the elastic constants of the paper is given.