Saturday, 30 May 2015

Bio Inspiration

1. Clingfish Offer Inspiration for New Medical Devices

The northern clingfish has a suction cup-like discs on the belly which can stick to wet and uneven surfaces. If these fish were scaled up to human size, the suction cup-like discs on their undersides would easily be strong enough to lift several cars! Hence, their sticking power can be of particular interest for new technologies such as medical devices.

The location of the disc makes the clingfish so suction-able. Clingfish is well able to cling to the surfaces which have various levels of roughness due to the layers of hairlike structures found at the edge of the disc. Frictional force acts between the edge of the disc and the surface that it is stuck to when they are contacted to each other.

Similarly, surgical tool mimic the clingfish’s technique to increase the efficiency of laparoscopic operation which require to work through very small incisions elsewhere in the body using a lighted tube. The procedure can now go as fast and easy when the internal organs or other tissues grip tightly in a narrow clamped space with the help of these medical devices.

2. Flexible Bullet Proof Armor Inspired by Fish Scales

The conventional familiarity when mentioned bulletproof vest are usually attributed to large, bulky, inconvenient and also heavy. Especially on the last two attributions, the weight could range from as light as 7.4kg to as heavy as 11.4kg. Where the issue with weight could be easily overcome with strength conditioning, there seemed to be no direct solution towards movement restrictions. It is understandable that, this disadvantage leads to a burden and difficulty upon physical task performance.

Issues related to such that the current design of bulletproof vest prevents user from properly bending their torso and it tends to irritate the rotator cuffs/ shoulder movements causing in discomfort that could possibly disrupt their focus upon task at hand; resulting in endangering their safety.

With several major fields in the industry that heavily relies on bulletproof vests such as the security services, astronauts, military and any other services that revolves around high threat activity where mobility is important, it is imperative that these vests does not pose any form of liability in motion to the user as they are the only thing standing in between high impact/velocity projectile or external implication of edged force and their lives.

As effective and safe as the bullet proof vest can be, it could not be ignored that there are still rooms for improvement for this product; especially upon the flexibility issue. Current designed seemed to face an issue where if flexibility is desired, effectiveness of penetration prevention had to be sacrificed; vice versa. Thus, the researchers at MIT took an approach through biomimicry; to design a bulletproof vest that is flexible enough to accommodate user’s fluidity in motion without sacrificing the effectiveness of the initial purpose; which is to shield from external puncture force.

The biomimicry is inspired by the nature’s fish hard scales which synergized well with its flexibility. Fishes are known to be flexible as it is the core for primary propagation for its locomotion in the water; swimming, through the generation of flexion waves.

Taking the base concept upon the synergy of hard scales versus flexibility, the research which was led by Assistant Professor Stephen Rudykh, successfully achieved to design a bulletproof armor that is flexible. The key lies in within the different layers of the armor which consist of two components; a soft tissue-like layer upon the inner section and a hard, bullet proof substance to constitute as the ‘armor’ upon the outer layer. These two components combined to create a protecto-flexibility property that is highly desired for bulletproof vests.
Multiple layers depicting the concept design.

 Professor Rudykh demonstrating the flexibility of the material
(hard scales over soft material)
Tests done on varying angles from 10 degrees (top), to 20 degrees (middle) and to 30 degrees (bottom) to observe the penetration resistance pattern. The arrangement were hard scales on top of soft elastic material, providing great flexibility.

As far as the progress goes, currently Professor Rudykh  and his team are materializing this design through 3D printing to allow for physical testing. On top of that, it has been claimed that the team had discovered a way to increase the penetration resistance by a factor of 40, while only sacrificing the flexibility of the soft material by a factor of 5.

 It is observed that the next milestone is to incorporate this design to military uniforms, further improving strength, providing better overall protection and enhancing flexibility as well. For the space suits, it would greatly benefit from the flexibility as it would pose far less resistance during spacewalks and increases the impact resistance making it impervious to micro-metorites. It is also recorded that Rudykh’s work had been published in the journal of “Soft Matter”

3. VIVACE hydropower

University of Michigan (UM) recently had patented MHK device, the VIVACE converter (Vortex Induced Vibration for Aquatic Clean Energy). VIVACE harnessed river or ocean current flow over its cylinder body to generate vortexes that push the cylinder up and down and thus generate electricity. This transformational renewable technology has low environmental impact, low installation cost and high energy efficiency which only require 2 to 3 knots of water currents to start operate. The inspiration of VIVACE come from observing the fish swimming inside the aquarium tank according to Dr. Michael Bernitsas of the University of Michigan’s department of marine engineering. When fish swims forward, they curve their body to collect the vortexes, and then straighten their body and curve to other side and create another vortex to allow them to glide along the vortexes which propel them forward. This phenomenon is called Vortex Induced Vibration (VIV) where vortices are formed and shed on the downstream side of a bluff body and hence creating a pressure differences that generate oscillatory lift. Besides, Cylinder oscillations are rather slow at about a cycle/sec which do not create physical impact on marine life. The YouTube video below shows how the VIVACE works under different knots of water current. VIVACE is a simple device which can generate high actual power and more cost effective than wind turbine. Table 1 below shows the comparison between Oscylator 33 comparisons to 1.5MW GE wind Turbine. The Oscylator 33 has lower rated power than 1.5MW GE wind turbine, however Oscylator has higher capacity factor than wind turbine. Capacity factor is the rated power over the average actual generated power throughout a year. The higher the capacity factor, the greater the power efficiency for a device. Moreover, the total cost to buy and install Oscylator 33 is lower than the wind turbines. Hence, VIVACE can be concluded as a more sustainable renewable energy product than a wind turbine when a design is inspired from the nature (Field et al., 2013).

VIV cylinder motion movement

Fishes apply VIV to swim

Table 1. Oscylator 33 (VIVACE) comparison to 1.5 MW GE wind turbines (Field et al., 2013).

References,. 'Tough, Flexible Material Could Protect Soldiers & Astronauts : ATS'. N.p., 2015. Web. 15 May 2015.
Mail Online,. 'Body Armour Based On A FISH Could Lead To Bulletproof Uniforms'. N.p., 2015. Web. 15 May 2015.
Rudykh, Stephan, Christine Ortiz, and Mary C. Boyce. 'Flexibility And Protection By Design: Imbricated Hybrid Microstructures Of Bio-Inspired Armor'. Soft Matter 11.13 (2015): 2547-2554. Web. 15 May 2015.
Field, D. O. E., Officer, C., Brodie, P., Field, D. O. E., Management, G., Kerry, S., … Mauer, E. (2013). DE-EE0003644 Advanced Integration of Power Take-Off in VIVACE Vortex Hydro Energy Final Scientific/Technical Report, 1–28.

Sunday, 3 May 2015

Literature Review

i) Armored catfish, Pterygoplichthys pardalis

According to Ebenstein et al. (2015), the Pterygoplichthys Pardalis armored catsfish has arrow shape (sandwitch-like structure) dermal plates cover their body to protect them from sharp tooth penetration caused by other predators. He studied the mechanical, chemical and structural properties of the P. pardalis by using tools like differential scanning calorimetry (DSC), scanning electron microscope (SEM)/energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Nanoindentation analysis and statistical analaysis. All these scientific tools are generally explained by the author in the Journal. The interested parts are, unlike most of the common fish have elasmoid fish scales, P. pardalis have a three dimensional “V” shape of dermal plates that 15 mm in length and 1.5 mm in thickness. Below figure shows the Hierarchical structure of the dermal armor of P. pardalis which are provided in the journal. The skin under the exterior protection layer (Dermal Plate) has a smooth texture, meanwhile the dermal plates are covered with the tooth-like elements called tubercles to protect against predators. Song et al. (2010) also reported that the tubercles have both penetration resistance and hydrodynamics ability. 

Figure 1. Hierarchical structure of the dermal armor of P. pardalis.

Dermal armour enables lightweight, flexible and tough ability to the common fish. However, in P. pardalis, the overlapping layers of arrow shape dermal plates containing porous inner matrix which provide toughening mechanism and flexibility that absorbing energy to prevent fracture of the outer lamellar layers. This overlapping structure is also implemented in some military armour due to its lightweight and flexibility. In conclusion, dermal plates provides different protection mechanism such as prevent predator tooth penetration, meanwhile porous inner matrix playing roles that absorbing energy from an attack and increase the fracture toughness (prevent fracture) of the dermal plates (Ebenstein, Calderon, Troncoso, & Torres, 2015)

ii) Shark’s Skin
By studying the microscopic structure of shark’s skin, it has been found that the surface of the shark skin is formed with many micro-riblets. Upon investigation, it is concluded that the micro-riblets, when aligned in the local flow direction, aid in the drag reduction of the shark hence enabling the shark to be one of the fastest fish in the sea. While aligned in the local flow direction, the micro-riblets acts in a way that it will reduces wall shear stress by altering the distribution of the flow field. Figure below shows the microscopic image of the shark skin with micro-riblets covering the surface.
Figure 2: microscopic image of the shark skin. (Ltd, 2015)

This phenomenon discovered by scientist has since been widely applied at the fuselage of aircrafts and outer surface of ships as it will reduce the drag experienced by the aircrafts and ships while moving through medium such as air or water. By doing so, less power will be needed by both transportation methods and energy could be saved. To put it into perspective, this application will not just save the cost of the transportation by reducing the fuel needed, but also eco-friendly to the environment as less pollutant will be emitted by the engines of both the ships and the aircrafts. Zhao et al. have performed a vacuum casting to replicate the micro-riblets of the shark skin. Through experiment, the prototype shows a promising 9.7% to 18.6% of drag reduction. The same technology was also adopted in the design and fabrication of the Speedo swimming suit. Through the biomimetic of a shark skin like swimsuit, Speedo claims that their Fastskin LZR Racer Elite 2 will have a 6% reduction in drag, which will increase the swimming speed of the swimmer.
Figure 3. Fastskin LZR Racer Elite 2 (Anon., 2015)

iii) Sharklet
In general conception, Sharklet is simply a type of plastic specifically designed to impede bacterial growth. This biomimicry based invention serves great purpose on fields with relatively high potential for bacterial infection such as the hospital. Serving its purpose upon impeding bacterial growth, the Sharklet could be measured as a successful method in purging out the spread of infection.

The inspiration came from observing the Galapagos Shark which does not exhibit signs of being inhibited by barnacle or microscopic algae upon the skin’s surface. Further study shows that the key lies in within the unique skin pattern under microscopic observation which consists of repetitive diamond shaped scales stacked partially amongst each other. Figure 1 portrays visual illustration of the shark’s skin pattern under microscopic pattern. 

Figure 4. Microscopic image of Sharklet pattern

Figure 5. Microscopic image of Sharklet pattern.

Under close observations, it has been discovered that these dermal denticles possess different gradients at a nanoscopic scale, inducing stress gradient upon the lateral surface during initial contact. This simple yet effective mechanism causes the foreign microscopic cells to experience disruption when attempting to settle due to the high requirement of energy needed to be expanded in order to equalize the stresses induced from the fluctuated gradient pattern. So to speak, a large amount of energy is required to inhibit on the surface which was thus deem unfavourable by the settler; from the result of poor thermodynamic efficiency, resulting it to search for an alternate surface with better compatibility to synergise with.

A study done by May et al. shows that the efficiency for these micro-patterned surface demonstrated the ability to reduce bacterial colonization up to 99.9% compared to an un-patterned surface. The aforementioned technology harvested from the holistic approach of biomimicry not only saved precious time and resource for R&D to solve one of the many issues mankind currently faced, but also deemed friendly towards the environment, human and cost efficient as the plastic material currently being widely used would receive minor modifications in terms of surface pattern implementation with varying gradients which is visible under microscopic observation. This breakthrough would be believed as a staggering contribution within the human association in preventing the spread of disease and promote a hygienic society for a better future.

iv) Arapaima Gigas

Figure 6. Arapaima Gigas 

Arapaima Gigas is known as one of the biggest freshwater fishes in the world which can be found in the Amazonian region, reaching a length of 2-2.5m and a mass of over 150kg. Biomimicry of Arapaima’s scales could use to develop new ceramics for armor and panels due to their high toughness and flexibility. The maximum tensile strength and Young’s modulus of the Arapaima’s scales are found to be 53.86Mpa and 1.38Gpa respectively (Torres, Troncoso, Nakamatsu, Grande, & Gómez, 2008. Besides, XRD and FTIR show that the scales are formed by collagen fibres reinforced with a mineral phase of calcium deficient hydroxyapatite. The morphology of the Arapaima Scales show a plywood pattern of collagen layers co-aligned within each individual layer rotating at angles of around 90° between each layer.

Figure 7. Hierarchical structure of the Arapaima gigas scales.
The Arapaima gigas scales have an outer layer that is highly mineralized where the inner layer is a laminate composite of collagen fibers which are formed by fibrils (Lin, Wei, Olevsky, & Meyers, 2011). Ceramic surfaces of constant thickness are strained when forced to follow a curved surface, but the grooves allow the scales to be bent more easily without cracking. The corrugations, the soft but tough internal layer and the hydration of the scales all contribute to their ability to flex while remaining strong. It’s an engineering solution that lets the fish remain mobile while heavily armored, and also allows the scales to bend and deform considerably before breaking.

Ebenstein, D., Calderon, C., Troncoso, O. P., & Torres, F. G. (2015). Characterization of dermal plates from armored catfish Pterygoplichthys pardalis reveals sandwich-like nanocomposite structure. Journal of the Mechanical Behavior of Biomedical Materials, 45, 175–182.

Anon., 2015. Speedo. [Online] Available at: [Accessed 29 April 2015].

Ltd, M. M., 2015. Insight for the european commercial marine business. [Online]
Available at: [Accessed 29 April 2015].

Lin, Y. S., Wei, C. T., Olevsky, E. a., & Meyers, M. a. (2011). Mechanical properties and the laminate structure of Arapaima gigas scales. Journal of the Mechanical Behavior of Biomedical Materials, 4(7), 1145–1156.

Torres, F. G., Troncoso, O. P., Nakamatsu, J., Grande, C. J., & Gómez, C. M. (2008). Characterization of the nanocomposite laminate structure occurring in fish scales from Arapaima Gigas. Materials Science and Engineering C, 28(8), 1276–1283.