In a discovery that reshapes how scientists understand liquids, researchers have shown that microscopic oil droplets suspended in water can fold themselves into precise, six-pointed star shapes while remaining liquid inside.
Liquids are typically expected to form smooth, round spheres. But in a new study scientists demonstrated that under carefully controlled temperature conditions, droplets can transform into highly symmetrical, star-shaped structures.
The research was led by Prof. Eli Sloutskin, from the Department of Physics at Bar-Ilan University, and Dr. Catherine Quilliet of CNRS/Université Grenoble-Alpes (France), with the participation of Dr. Alexander Butenko of Bar-Ilan University.
The team found that as the droplets are cooled, their surface undergoes a phase transition, forming an ultra-thin crystalline shell only about two nanometers thick. While the interior remains liquid, this thin outer layer behaves like a flexible, but nearly unstretchable, elastic skin. When reheated, the shell bends and folds -- much like origami -- creating a three-dimensional, lens-shaped hexagram.
“We discovered that this dramatic transformation happens purely through folding,” says Prof. Eli Sloutskin. “Unlike previous droplet shape changes we studied over the past decade, this process does not involve the movement or rearrangement of structural defects in the crystalline layer. The shell remains topologically intact. The droplet reshapes itself simply by bending.”
Solving a Longstanding Puzzle
The work builds on earlier research from 2016 showing that liquid droplets can form faceted, polyhedral shapes. However, concave, six-pointed star shapes had only been observed sporadically and could not be reliably reproduced. Their formation mechanism remained unknown.
By designing a precise temperature protocol and combining optical microscopy, electron microscopy, macroscopic experiments, and theoretical modeling, the researchers identified the physical mechanism responsible for this unusual geometry. They demonstrated for the first time how to produce the lenticular hexagram shape reliably and in a controlled manner.
The key insight was to treat the droplet surface as a thin, self-folding elastic shell with structural defects located at specific positions, bringing together interfacial physics, elasticity theory, and topology.
A New Route to Shape Transformation
One of the study’s biggest surprises was that the six-pointed star forms upon heating, not cooling, and through a completely different mechanism than previously observed droplet faceting transitions.
“For years, we saw shape transitions driven by defect motion or defect creation in the interfacial crystal,” said Prof. Sloutskin. “Here, the crystalline shell remains intact. The transformation happens purely through bending and folding, revealing a fundamentally new route for shape change in elastic interfacial crystals.”
The spontaneous emergence of such a highly symmetric and culturally familiar shape from simple physical principles was also striking.
Broader Significance
Beyond its visual appeal, the discovery improves understanding of how geometry, elasticity, and interfacial physics interact at microscopic scales. The ability to control droplet shapes may also help advance the design of structured materials, nanoparticles, and potential biomedical applications. The findings may further be relevant to biological systems where thin membranes and shells undergo controlled shape changes.
The study, published in Physical Review Letters , was supported by the Israel Science Foundation.
Lenticular Hexagon-to-Hexagram Shape Transformation: Nano-Origami in Liquid Droplets
27-Feb-2026