Researchers at Shinshu University in Japan have uncovered the secret behind the glossy appearance of the hardy ice plant (Delosperma cooperi). Their findings could inspire the development of innovative reflective materials for future optical applications.

A Natural Strategy For Controlling Light

Nature offers many examples of sophisticated light manipulation. Butterfly wings, bird feathers and flower petals all use microscopic surface structures to control how light is reflected, scattered and absorbed. These optical effects often help organisms attract pollinators, communicate or protect themselves from environmental conditions.

The hardy ice plant, a succulent native to South Africa, is one such example. Its flowers display a distinctive glossy sheen. To understand how this effect is created, researchers led by Professor Hiroshi Moriwaki studied the flower’s petal surface in detail.

The team used scanning electron microscopy, confocal laser microscopy, optical digital microscopy and reflectance measurements. They also produced transparent resin replicas of the petal surface using silicone moulds and UV-curable resin. This allowed them to investigate whether the effect could be reproduced artificially.

Parabolic Surface Structures Create Gloss

The researchers discovered that pigments and surface waxes do not create the glossy appearance. The petals remained glossy even after losing their reddish-purple colour and after treatments that removed waxes from the surface.

Instead, the effect comes from the petal’s microscopic structure. The surface contains tiny groove-like ridges with a parabolic shape. These structures both reflect and concentrate light.

According to Professor Moriwaki, the upper surface reflects light over a broad area, much like a traffic mirror. The underside concentrates light that passes through the petal. Together, these effects create a strong gloss that remains visible from many viewing angles.

The researchers believe the glossy surface may help the flower attract pollinators while making efficient use of available sunlight.

Inspiration For Biomimetic Materials

Many flowers create visual effects through prism-like structures or thin-film interference. The hardy ice plant uses a different strategy. Its unique parabolic architecture manipulates light without relying on those mechanisms.

This discovery is relevant beyond plant biology. The researchers demonstrated that similar optical effects can be achieved in thin materials by replicating the petal’s surface geometry. Their resin replicas successfully reproduced the reflective properties of the natural structure.

Although large-scale production remains a challenge, the research highlights the potential of bio-inspired surface engineering. Future applications could include reflective coatings, optical films, sensors and other advanced materials that control light efficiently without conventional prisms or glass beads.

By translating natural surface geometries into engineered materials, the study demonstrates how biomimicry can inspire new approaches to optical design and material innovation.

Source: Shinshu University / EurekAlert!
Photo: Didier Descouens