Acutely triangulated, stacked, and very ununfoldable polyhedra.
E. Demaine,
M. Demaine, and
D. Eppstein.
arXiv:2007.14525.
Proc. 32nd Canadian Conference on Computational Geometry, 2020, pp. 106–113.
We construct non-convex but topologically spherical polyhedra in which all faces are acute triangles, with no unfolded net. This is the third in a sequence of papers on ununfoldable polyhedra; see also "Ununfoldable polyhedra" and "Ununfoldable polyhedra with 6 vertices or 6 faces".
(CCCG'20 ununfoldability video – Blog post: Polyhedra with convex unfoldings)