Literature Review - Bioinspiration

A hedgehog, although small, has its own unique feature to survive in the wild. The most obvious features is its spine or quill. The spine of the hedgehog is not the same as the one that a porcupine has. The difference between them is that a porcupine’s quill is detachable and is hollow inside, on the other hand, the hedgehog has a smaller, non-detachable and solid quill.

Hedgehog is a clumsy mammal and often falls from high ground. Thanks to its spine, a hedgehog can fall up to 10 feet and remain unharmed. The protective mechanism of a hedgehog is that, it tucks itself in and forms a ball shape, exposing the spines around the core. The spine then act as a spring, absorbing all the impact.

Despite its poor eyesight, its other senses compensate for it. The nose of the hedgehog is highly sensitive, it is its most valuable asset. It uses its nose to hunt for its dinner. It also picks up the scent of an intruder. This allows them to act accordingly. This is why hedgehogs can be seen sniffing around as they walk.  

As mentioned above, the hedgehog’s spine is very useful as a shock absorber. The helmets in the market today are generally inadequate on absorbing multiple hits. A helmet can be split into three layers, the outermost is made out of polycarbonate, middle layer for shock absorbency and the innermost layer for paddling. The improvements to a helmet can be done on the middle layer.

Research has found out that most of the concussions occur by receiving an impact on the side of the head causing a rotational movement. This rotational movement is then transfer to the brain, resulting in a change in position from its regular position. The average helmet in the market is not effective on absorbing the rotational impact. However, this can be changed by using the spine of the hedgehog. Research has be done by putting the spines close to each other and twirling them around in multiple direction shown in figure 1. As one of the spine receives an impact, the force will then transfer to the neighbour spine, causing a domino effect, which will greatly distribute the impact force on a larger area. 

Figure 1: Prototype of hedgehog inspired material.

Another example will be the hedgehog’s self defence mechanism is where it rolls into a ball. Although parachutes these days is effective for slowing down the falling velocity, it requires a minimum height and pressure to generate enough drag to reduce the velocity. A medium with low pressure such as moon, it is ineffective to use parachute, same goes for bungee jumping, where the height is too short for the parachute to work efficiently.

Nevertheless, a hedgehogs self defence mechanism might be a solution to this. A suit with a spine mechanism can be implemented to save lives. It can be deployed like an airbag in the car. When the person is experiencing certain acceleration, which resemble the acceleration on free fall, the spines will automatically deploy and form a ball shape spine to reduce the impact. 

Figure 2: Hedgehog in its defensive position.

Lastly, hedgehog has a great sense of smell. This is mainly due to its long and slim nasal cavity. This allows large amount of chemical particles to be stored in the nasal cavity. The larger the amount of the particles, the higher the sense of smell. Furthermore, due to its slim and shallow cavity, it increases the concentration of the chemical particles, further improving the sense of smell. Other than that, its moist nose also help the chemical to dissolve faster for the smell receptor to pick up the chemical particles.

By applying this knowledge, we can improve the sense of smell on a human being. A mask can be designed to improve people who has their sense of smell weaken over the years. Losing sense of smell, can be disastrous for a person. Not being able to taste your favourite food, is like taking away one of the greatest pleasure a human can have.