Scaffold with gradually changing porosity


  • Scaffold with gradually changing porosity creates better mechanical conditions for bone healing than with uniform structure.(In a medical context, a scaffold is a 3D porous structure made from biomaterials that acts as a temporary support).


  • The Functionally Graded (FG) scaffold is a scaffold where the porosity, stiffness, or composition varies smoothly across its volume to better match how natural bone behaves.


  • Scaffolds with increasing porosity (more holes) toward the metal plate transferred stress better, The improvements were strongest for titanium Ti-6Al-4V material. The more gradual the porosity change, the better the mechanical distribution inside the scaffold.


  • The authors used Finite Element Analysis (FEA).


  • To control porosity, they create a third order polynomial relation between strut thickness (S) (thickness of the bars of the lattice) and porosity(n).

  • This relationship was used to design scaffolds with precise porosity gradients.


  • They measured octahedral shear strain (ε_oct) : this measure combines tension, compression, and shear effects into one value.

  • Uniform scaffolds with 50% porosity exhibited relatively low octahedral shear strain values, particularly adjacent to the fixation plate, indicating regions of stress shielding while Functionally Graded scaffolds show progressively higher strain levels and more extensive strain distribution within the scaffold.


Icy moon’s ice shell and subsurface ocean circulation

On an icy moon like Europa or Enceladus, the ice shell above the water may vary in thickness. The ice is thicker at the equator and thinner at the poles, this slope produces pressure and temperature differences at the ice–ocean boundary.

These differences create density (buoyancy) gradients in the upper ocean, which drives currents and baroclinic eddies (swirling motions) in the ocean.


In subsurface oceans (like on Europa or Enceladus), vertical mixing stirs heat between deep and shallow layers. This energizes baroclinic eddies, swirling flows caused by sloping density layers. Together, they create a circulation loop that transports heat from polar regions (thin ice) toward the equator (thick ice). But when topography (the shape of the seafloor or ice base) dominates, it can either suppress or enhance this heat flow depending on how dense layers are arranged.


ocean flow is modeled using the Boussinesq approximation model.


The differential rotation velocity of an ice shell or core depends on tidal, gravitational, and rotational forces. differential rotation velocity is very low — meaning the ice shell and the underlying ocean rotate almost together, with only tiny relative motion.


Source: https://arxiv.org/html/2510.25988v1


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