When symmetry breaks in tiny spaces

In physics, some of the most striking phenomena emerge when perfect symmetry shatters. This principle, known as spontaneous symmetry breaking, underlies everything from the Higgs mechanism that gives particles mass to the twist of DNA and the handedness of seashells. Researchers have now uncovered a particularly fascinating stage for this phenomenon in liquid crystals—soft materials that flow like liquids yet maintain molecular order like solids. You’re probably reading this with the help of liquid crystals, as computer monitors and smartphones rely of their properties. With the observation now made by an international research team, they might find even wider usage in energy storage or conversion or tunable lenses.

There are different types of liquid crystals: “regular” ones with a rigid, rod-like molecular core and ones with a bent core. Their asymmetrical, banana-like shape allows them to self-assemble in chiral superstructures  – helices with left- or right-handed twists in their structure – even though the molecules themselves are not chiral. Chirality means “handedness”: an object is chiral if it cannot be superimposed on its mirror image, like how your left and right hands are mirror images but not identical. This spontaneous emergence of handedness, coupled with other unusual properties like giant flexoelectricity and strong electro-optic responses, makes them promising for advanced applications in energy conversion, adaptive optics, and responsive nanosystems.

An international team including scientists from Ukraine, France, Poland and Germany trapped these exotic molecules inside pores just billionths of a meter wide and watched how they arranged themselves. They found that this process called nanoconfinement has a massive influence on the behaviour of the liquid-crystal molecules. The team investigated the bent-core dimer CB7CB confined within anodic aluminum oxide (AAO) and silica membranes. Their precisely engineered cylindrical nanochannels ranged from a few nanometers to several hundred nanometers. Using high-resolution polarimetry to probe their optical anisotropy, a measure of how a material affects light depending on the light’s direction and the state of its polarisation, the team revealed how geometry alone can mimic the effects of applied electric fields. A material containing nanopores can thus achieve the same effect as an electric charge: driving phase transitions and altering molecular order. They present their work in the journal SMALL.

Above a certain pore size, the CB7CB assembles into a helix. However, as the pores became smaller, the ability to form such an order collapsed, leaving only one achiral state. The transition was tracked with the help of a laser. “We prove that we can manipulate the photonic properties of liquid crystals by confinement,” says Patrick Huber from DESY and Hamburg University of Technology, one of the corresponding authors of the work. “Right now, this is first and foremost knowledge-driven research, but the potential for this technology is huge.”

By squeezing bent-core nematics into nanoscale pores, we not only revealed how confinement induces or suppresses chirality and order, but also discovered a powerful parallel to electro-optic tuning,” Huber says. “This opens new pathways for designing nanofluidic devices, sensors, and adaptive optical systems that harness symmetry breaking in soft matter,” adds first author Andriy Maksym, a PhD student from Lviv Technical University (Ukraine).

“Ultimately, this research shows how nanoconfinement acts as a new kind of ‘field’, enabling scientists to systematically manipulate the self-assembly, chirality, and optical behaviour of liquid crystals,” says Andriy Kityk from Czestochowa University of Technology in Poland. “Just as spontaneous symmetry breaking gave rise to new physics in the early universe, here it promises to enable next-generation functional materials at the nanoscale.”