Bio-inspiration - Turtle Shell used as Body Armour

Protective armours were found in nature a long time ago and they consist of several number of designs. However, these designs are rarely structurally rigid: nature often prefers multi-layer material systems providing maximum impact protection at a weight that has the possibility of exhibiting high fracture toughness and impact resistance. The materials for armours are usually from ceramics and polymer matrix composites whereby composite armour is made of a hard strike ceramic face made of tiles as well as fiber reinforced composite backing plate. The purpose of the front ceramic layer is to prevent the high pressure forces on the backing composite plate by projectile deformation whereas composite backing plate is utilized in absorbing its kinetic energy.

Armours can be mimicked from the turtle shells whereby the shells are covered by thin keratinous wavy multi-layers and termed scutes. These keratins are useful in such a way that the proteins from keratins are able to protect the epithelial cells from damage. Hence, these features serve as a defense mechanism whenever they are attacked by predators. Similarly, when these feature is applied in body armours as well as shields, it will be able to protect the soldiers from incoming attacks during combat. Here are 2 examples: Traditional and modern day body armour:

Figure 1. Traditional body armour worn by Roman soldiers. The shield is design according to the shape of turtle shell

Figure 2. Modern military body armour from Korea Military Force (KMF)

In the present day, the analysis of body armour evolution in turtles results in several design principles:

1.      Maximize size of body armour

2.      Create smooth surfaces

3.      Create multilayer body armour

4.      Introduce shock absorbing layers

5.      Minimize weight

6.      Maximize articulation

The Romans have imitated the function of the turtle shell with military maneuver in which soldiers marched in a rectangular formation apart from body armour:

1.      Head holding shields at the front

2.      Side holding shields at the side

3.      Soldiers in the middle holding shields over their heads

Figure 3. Soldiers in rectangular formation with their shield to cover from external impact

References

1. B. Achrai, B. Bar-On, and H.D. Wagner, “Biological armors under impact-effect of keratin coating,     and synthetic bio-inspired analogues,” Bioinsp. Biomim, vol. 10, 2015.

2. T Arciszewski, and J. Cornell, “Bio-inspiration: Learning Creative Design Principal ,” 

Bio-inspiration - Turtle Shell used as Chinese Medicine

The turtle shell is commonly use in food and chinese medicine to cure certain disease or used as nutritional supplement. Below is a video that showed one of the dessert that made by turtle shell, Gui Ling Gao (also known as turtle's jelly)

Bio-Inspiration- Turtle's Shell used as Chinese Medicine

Turtle shell has been used as both food and medicine since ancient time in China and is recorded in the Shennong Bencao Jing, which is a medical handbook that being used by the ancient physician for centuries as a standard guideline for chinese medicine practice. According to the chinese medicine, turtle shell is often use in rehmannia-based formulas that nourish the Yin and calm the Yang. In modern study, it found that turtle shell does provide a significant hormone effect to human body which caused by the nutritional components (calcium and protein) contains inside the turtle shell.  

Figure 1. The cover page of Shennong Bencao Jing. It is a medicinal handbook that commonly used in the chinese medicine practice

The bottom part of the turtle shell, which is also known as plastron, is the desire part which has significant pharmacological value instead of the top part of the shell (also known as carapace). Although study showed that there are twice the amount of gelatin (desired bioactive compound) as the plastron from the carapace, but the consumption of plastron is still higher than carapace for chinese medicine. The plastron is separated from the animal carcass and cook in 20% lime water in high temperature and the water is consumed by the patient. In addition, vinegar processing is consider another well known method that able to boil the collagen from plastron into gelatin.

Figure 2. Chemical structure of gelatin

The major chemical constituents of turtle shell (plastron and carapace) are calcium, collagen, gelatin, and a trace amount of fats, magnesium, zinc, vitamin D. The calcium compound make up the major part of the shell and  is able to cure calcium deficiency-related disease such as bone disease ricket, which is caused by impaired deposition of bone calcium. According to a case study, it was reported that calcium provided by the turtle shell has similar effect as the calcium supplement such as cod liver oil and calciferol. Moreover, the gelatin (make up 7% of the plastron) converted from collagen in boiled water is develop to inhibit arthritis, angiogenesis. In addition, the gelatin polypeptides (fragments that produced from digestion) is able to treat bleeding as well. Moreover, a turtle shell-based formula that combined with methimazole to treat Grave's disease showed that 14 out of 25 patients had complete remission of symptoms at the end of the treatment. The raw turtle shell is also reported to traditional use for treating vertigo, tinnitus, deafness, headache, and convulsion.     

Figure 3. Actual view of plastron of a turtle

References

1. S. Dorr, "Tortoise Shell: with Brief Reports on Treating Aplastic Anemia and Parkinson's Disease", Itmonline.org, 2016. [Online]. Available: http://www.itmonline.org/arts/tortois2.htm. [Accessed: 04- Jul- 2016].

   

Bio-inspiration from Turtle's Shell - Skiboard

Skiing is a type of recreational activity where participants use skis to glide on snow. The ideal ski (also known as skiboard) can withstand high levels of pressure in turns and also able to maneuver. These two features usually require two different types of skis:

1.       Expert skiers that preferred rigid skis

                                 2.       Intermediate-level skiers that preferred flexible ones

But a new type of ski is able to combine the two different features of the skis into a design based on the turtle scales. This design allows the skis to be able to maneuver while entering and exiting turns, at the same time stiffen up in the middle of several turns to improve the skis’ grip on the snow. The turtle shell design was a joint effort based on a research institution from École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, Institute for Snow and Avalanche Research (SLF) and a Swiss ski manufacturer.

Figure 1. Turtle's shell structure and cycling-loading analysis trend result

The idea of mimicking the morphology of turtles was introduced by Véronique Michaud, a researcher at EPFL. She stated, “The scales of a turtle interlock, like a jigsaw puzzle, and they are connected by a polymer. When turtles breathe, the scales separate slightly and the shell becomes flexible. But when an external shock occurs, the shell tightens and stiffens”. 

The new ski design was conducted by embedding aluminum plates with a snake like shape fissure into precise locations at both ends of the skis. When the skis bend in one turn, the plates at both sides of the gap come together and the ski stiffens, allowing the skier to achieve stable and precise turns. As the skier comes out from one turn, the gap reopens allowing the ski to be more flexible again and easy to handle. Hence, the alminum plates function like scales and a special type of rubber between the plates is similar to the polymer exist in the turtle shell. The ski design was shown as follows:

Figure 2. The mimicking of turtle's shell structure on skiboard. 

The newly designed ski was proven by Olympic ski champion, Tina Maze as she attempts to utilize the new design for a ride. She stated, “As the pressure on the skis gradually increases during turning, the skis really gripped the snow and were stable. I was impressed by the ease with the plates coming together and separate.”

The new design also improves the safety during the turn which prevents skiers from falling down causing severe injuries, and worst case, it could cause fatality since skiing is hurtling down with steep slopes.

References

1. L. Pessina, "Ski design inspired by turtle scales", MEDIACOM, 2015. [Online]. Available: https://actu.epfl.ch/news/ski-design-inspired-by-turtle-scales/. [Accessed: 03- Jul- 2016].