Inspired Design

This post focus on the proposed design that can be used in the industry inspired by the crocodile. 
As we know, crocodiles have very tough epidermal scales that consist keratin and bony plates for protection. The scales are unique as they result from cracking of the hardened skin rather than their shape being genetically determined.

Dome pressure receptors (DPR) or Integumentary Sensory organs (ISOs) are the sensors on the scales with fingertip sensitivity. Some crocodile (eg. Caiman) has the sensors on the head since embryos stage before the skin start to crack and form scales while some other crocodile (eg. Nile Crocodile) has developed the sensors all over their body. The DPR contained mechano-sensory receptor to detect touch, thermo-sensory receptor to detect temperature and chemo-sensory receptor to detect chemical stimuli.

DPR allows the crocodiles to be capable to hunt prey in the dark by detecting the surface pressure waves. The thermal sensors help them to keep their body temperature by basking under the sun and cooling in the water. At the same time, the chemical sensitivity allows them to find suitable habitats.

By inspired by mechano-receptor sensors of crocodiles, piezoelectric pressure sensors with direction detection function can be invented for autonomous underwater vehicles (AUVs). AUVs are used for underwater surveying to detect submerged debris, rocks and obstacles that may threaten navigation for commercial or recreational crafts. Among the common sensors used in market now such as optical sensors and sound navigation sensors faces issues. In turbid or deep water, the visibility is very low that optical sensor could not perform well while sound sensors will face blind zone and the intensive sound emmited might harm the marine lives. Therefore, passive sensing system can be employed to minimize disturbance to the environment while effectively collecting information.

On the outer skin layer of DPR, mechanoreceptors are separated into rapidly adapting (RA) and slowly adapting (SA). RAs are stimulated by the onset and offset of the stimulus while SAs are stimulated whenever the existence of the stimulus. The RAs are accountable for oscillation sensing and SAs are responsible for the steady mechanical signal detection. By examining the information obtained, crocodiles are able to locate the direction of disturbance in water in 3D space.

The piezoelectrical sensor can be designed according to the inspiration from DPRs:
1. Dome shape of DPRs
2. Several receptors on a single DPRs
3. Separate domes for RA and SA receptors


The concept of the sensing system will have a 3D printed dome shape that allows multiple receptors allocate at different position on the hemispherical dome such as center, north, east, south and west to detect the direction of disturbance. There will be individual domes for both RA and SA receptors in order to detect different stimulation. The center piezoelectric sensor will detect the dynamic pressure changes like the mechanoreceptors in DPRs of crocodile while the other 4 sensors play the role to detect the 3D orientations.
Figure 1: 3D printed dome

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