Desk Staples Reveal Reversible, Shape-Shifting Material Behavior

CU Boulder researchers found that ordinary office staples exhibit a controllable switch between rigid and flowing states driven by particle geometry and vibration. A two-legged staple geometry yields strong interlocking; 90-degree crowns initially entangle more densely than 20-degree variants, but after about 36,000 vibration cycles the 20-degree staples gain much stronger bonds, enabling tensile strengths over 100%. Under confinement, vibration promotes entanglement; on open surfaces it disperses into a flat layer. This reversible behavior could enable assembly/disassembly of structures for construction and robotics, with ongoing work exploring even more effective legged designs.