Hebrew University Chemists Glued Ice to Plant Nanocrystals With a Designer Protein and Got a 'Super Ice' as Strong as Concrete. It Absorbs 70 Times More Energy Than Ordinary Ice Before It Breaks.

Ice is cheap, abundant and, under compression, surprisingly strong. Its problem is that it fails badly. A small crack can run through a block in an instant and shatter it with no warning, which is why nobody builds with it. A team at the Hebrew University of Jerusalem now says it has fixed that failure mode at the molecular level, producing a reinforced ice it calls BioPykrete that is roughly 10 times stronger than ordinary ice under compression and absorbs about 70 times more energy before it gives way.

The work, published in Colloids and Surfaces B: Biointerfaces and led by Prof. Ido Braslavsky of the university's Robert H. Smith Faculty of Agriculture, Food and Environment, starts from an old idea. During World War II, British researchers developed Pykrete, a mixture of ice and wood pulp that was tougher and slower to melt than plain ice, and briefly floated the idea of building aircraft carriers out of it. Braslavsky's group shrank the wood pulp to cellulose nanocrystals, tiny stiff rods extracted from the same material that gives plant cell walls their rigidity. As the water freezes, the nanocrystals link up into a three-dimensional scaffold around microscopic pockets of ice.

The new ingredient is the glue. The team engineered a chimeric protein with two working ends: one domain is an antifreeze protein, AFPIII, that binds to the surface of ice, and the other is a cellulose-binding module, CBM3a, that latches onto the nanocrystals. Stitched together, the protein anchors the cellulose network to the ice it is embedded in. "We wanted to go beyond simply mixing fibers into ice and instead control how the different materials connect at the molecular level," Braslavsky said. "The result changes not only how strong the ice is, but also how it breaks. Instead of suddenly shattering, it can absorb much more energy and deform gradually."

That change in failure mode is the point. In plain ice a crack, once started, has nothing to stop it. In BioPykrete a growing crack runs into the cellulose scaffold, which acts as an obstacle; because the protein pins that scaffold to the ice, tearing or deforming the network costs extra energy, and the crack is arrested or deflected rather than allowed to run. In compression tests on samples 2 centimeters across and 1 centimeter high, the composite reached strengths comparable to conventional concrete. Adding the two-ended protein doubled both the strength and the energy absorption compared with an ice-and-cellulose mix that lacked the molecular bridge. Electron microscope images of freeze-dried samples show the difference as a change in the scaffold's pore structure, measured across eight sections of each material.

The researchers are not proposing ice skyscrapers. They see the material as a candidate for construction in the Arctic and Antarctic, where hauling concrete and steel is expensive and where the raw ingredients, water and plant cellulose, are cheap, biodegradable and low-carbon. Before that can happen, they need to know how BioPykrete behaves over months and years, how it survives repeated freeze-thaw cycles, and whether it creeps under sustained load the way ordinary ice does. Follow-up studies will track how cracks actually move through the composite and test other proteins and freezing protocols to push the numbers higher.

For now it is a proof of concept: take the most abundant solid on the planet's cold regions, add a plant-derived skeleton and a protein designed to hold hands with both, and the result stops shattering and starts behaving like a building material.