In the wild, felines occupy the top of the food chain. They are formidable predators. Even a large tiger can move silently and stealthily thanks to the anatomy of its paw pads.

These pads , much larger than those of canids (dogs, wolves, foxes, etc.), are extremely elastic and absorb the slightest vibration or shock. Their structure is particularly interesting to study and opens up numerous possibilities for innovation through biomimicry.

Felines are digitigrade: they move on the tips of their toes. This makes them more discreet and agile, like masters of the hunt.

Their paw pads are essential for this. Soft and velvety, they feel the slightest vibrations in the ground, conceal their presence when moving, and are also extremely sensitive, allowing felines to identify the texture of their prey. Despite this, they are strong enough to support the cat's entire body weight.

What is the secret of these mysterious pads? They are made up of numerous elastic fibers embedded in adipose tissue, that is, tissue containing fat cells, which is tightly packed and dense. The thick outer surface, the epidermis, consists of several layers, including the stratum corneum, composed of many layers of keratin cells, the same proteins found in our nails. Beneath this lies the more flexible dermis, rich in sensory receptors, and finally, the subcutaneous tissue (adipose tissue) acts as a shock absorber and thermal insulator thanks to the juxtaposition of numerous fat cells.

This multi-layered structure can inspire vibration damping systems in many industrial parts and components , from aeronautics to automotive, including household appliances and/or railways.

Image credits: ©Chris Hubbard, Virginia Naples, Erin Ross, Burcu Carlon

Spider silk is renowned for its unusual combination of lightness and extreme strength, sometimes surpassing that of steel. Because of these properties, researchers have developed materials inspired by spider silk that are both strong and lightweight.

Until now, the acoustic properties of spider webs had not been explored. However, it has been discovered that the webs possess remarkable acoustic advantages. The web's architecture, made up of concentric circles or "rings," combined with the varying elastic properties of the radial and circumferential silk, is capable of attenuating and absorbing vibrations across a wide range of frequencies, despite its lightness.

Based on this complex natural architecture, a team of researchers from Italy, France, and the United Kingdom published their research on a bio-inspired acoustic metamaterial in 2016. This material possesses a specific periodic architecture that gives it remarkable properties such as blocking sound waves and mechanical vibrations.

This bio-inspired metamaterial is composed of square meshes containing resonating rings and supporting ligaments that radiate outwards from the center of the rings. According to numerical modeling, this new concept inhibits low-frequency sounds more effectively than other existing metamaterials.

This opens the door to entirely new applications through biomimicry, particularly for the construction of bridges or earthquake-resistant structures in architecture or in the design of innovative lightweight vehicles with vibration-damping and shock-absorbing structures.

Image credits: ©Marco Miniaci, Anastasiia Krushynska, Alexander B. Movchan, Federico Bosia', Nicola M. Pugno'

The grapefruit is a very heavy fruit: its mass can reach 6 kg. Once ripe, it falls from its tree and drops ten to fifteen meters, without cracking on impact.

Its skin possesses a remarkable capacity to absorb shocks and neutralize vibrations. Experimental results show that up to 90% of the impact energy is dissipated during its free fall.

The outermost layer of its structure, called the exocarp, is dense and rigid. Conversely, the part between the skin and the segments, called the mesocarp, is less dense and porous. It is filled with intercellular air and acts like a compressible foam.

The pore density gradually increases between the mesocarp and the exocarp, making these two parts difficult to distinguish. Therefore, there is no abrupt change in structural properties between the tissues that could lead to their separation.

The PROSE (Product Synthesis Engineering) laboratory at Texas A&M University developed a finite element model based on the non-uniform porosity of grapefruit peel . The model simulated an aluminum foam with 66% of the pores dispersed within 0.6 cm of the top and bottom surfaces of the foam.

To test the effectiveness of the porosity distribution, the team simulated dropping the foam onto its upper surface from a height of 1.5 meters, then measured the stress distribution. The shock caused by the impact was primarily absorbed by the upper surface and did not propagate completely to the lower surface, demonstrating shock absorption properties similar to those of grapefruit.

This foam design is a remarkable illustration of biomimicry. It could be useful in applications involving significant shocks or vibrations. In the automotive field, for example: improving vehicle damping and reducing vibrations in the transmission, internal mechanics, engine, or wheels.

Image credits: ©Ortiz J, Zhang G, DA McAdams