“ Untangling the mechanics and topology in the frictional response of long overhand elastic knots ” — Supplemental Information —

In this section, we provide specific information on our experimental apparatus. For all of our experiments we used a universal testing machine (Instron 5943, Norwood, MA) with a 10 N low-profile static load cell (2530 from the same manufacturer). The displacement and force resolutions were 10−4 mm and 10−4 N, respectively. Our experiments involved measuring displacements and forces of ∼ 10 mm and ∼ 1 N. The knots were tied in Nitinol rods (Nitinol Devices and Components, Inc). The material of the rod was superelastic Nitinol alloy SE508 with Young’s modulus, E = 67.50 ± 0.25 GPa, that was determined by a tension test where the force signature from a gradually imposed extension on a straight rod in the universal testing machine was recorded using a 1 kN load cell. As mentioned in the main text, one extremity of the rod was clamped to a base that was fixed to the lab frame and the other end was attached to the load cell of the universal testing machine. The rotation of the rod at both the ends was fixed. The rod was aligned vertically (along the direction of gravity) during the tests; however, the weight of the rod was negligible compared with the registered force signatures. All the force vs. extension measurements reported in the main text are reproducible which we ensured by repeating the experiments at least 3 times. We also performed representative experimental trials at different extension rates, ė = {0.5, 1.0, 2.0}mm/s, and did not find any systematic deviation. The experiments reported in the manuscript use a rate of ė = 1 mm/s.