by gravity, the top of the strand has more weight under it than the tip, which has none. Thus, if the weight on a hair is too great for its innate curliness, the curl will fail and become either straight or helical, depending on the strand's length and stiffness.
Miller created flexible, thin rods using molds as small as a bottle of Tabasco sauce and as large as the columns. He injected a rubber-like material inside hollow flexible tubing wrapped around these molds. Once the rubber material cured and the tubing was cut away, Miller and Reis had flexible polyvinyl thin rods whose natural curvature was based on the size of the object around which they had been wrapped. The study appears in the journal Physical Review Letters.