On the smallest scales, ordinary materials behave in ways that seem to defy the laws of physics. But these apparent contradictions reflect the minute details we\u2019ve yet to discover in nature\u2014as demonstrated by a new finding showing how solids can support wave-like shapes we typically see trailing behind boats on water.<\/p>\n
In a recent Physical Review Letters study, Harvard researchers describe how it\u2019s possible to engineer steady V-shaped wakes that ripple across the surfaces of ultrasoft, elastic materials like gels or biological tissue. Based on lab experiments, the team developed a theoretical model to explain this behavior, bridging two classical theories of fluid and solid surface-wave physics. This renewed perspective on solid physics opens new pathways for designing natural and engineered soft materials, particularly for medical purposes.<\/p>\n
Wakes, waves<\/h2>\n
The latest findings highlight a previously overlooked link between Kelvin\u2019s wake patterns and Raleigh waves, known to appear in fluids and solids, respectively. Both appear in very familiar contexts.<\/p>\n Kelvin wakes, first explained by the eponymous Scottish mathematician, are the V-shaped ripples that form behind boats or waterfowl gliding across water. Raleigh waves, on the other hand, refer to fluctuating motions across the surface of solids, such as the seismic waves produced by earthquakes.<\/p>\n Physicists previously assumed that the two were fundamentally different phenomena, according to a Harvard statement on the findings. However, the team behind the new study wondered if things would play out differently for soft elastic solids, which have a distinct, \u201cdelicate interplay between inertia, elasticity, gravity, and capillarity\u201d that could potentially mimic the physical properties of both solids and liquids, according to the paper.<\/p>\n \u201cI suspected that there ought to be a natural way to smoothly interpolate between the behavior of surface waves on solids and fluids,\u201d L. Mahadevan, the study\u2019s senior author and an applied mathematician, said in the statement, \u201cpartly inspired by watching boat wake along the Charles, where I walk almost every day.\u201d<\/p>\n Mahadevan and colleagues first set up a large tank filled with an ultrasoft hydrogel, using a thin air nozzle as the pressure source. The team then recorded any noticeable changes in the hydrogel\u2019s surface, plotting the angle of the V-shaped disturbances against other metrics like the velocity of the pressure source.<\/p>\n![\"Raleigh](\"https:\/\/gizmodo.com\/app\/uploads\/2026\/04\/raleigh-wave-336x177.jpg\")
Testing the bridge<\/h2>\n