Reversed Engineering Worksheet.

This week, the new design are discussed in detail from the engineering aspects.
Piezoelectric Sensor

Piezoelectric sensor is an electrical devices which converts mechanical energy to electrical energy to measure changes in pressure, acceleration, temperature, strain or force. There are many types of piezoelectric sensors namely piezoelectric accelerometers, piezoelectric force sensors, piezoelectric pressure sensors and etc. and they are widely used in the industry for quality assurance, process control and research and development. Various application such as in medical, aerospace, nuclear instrumentation and tilt sensor in consumer electronics or pressure sensor in touch pads of mobile phone utilize piezoelectric sensors. Piezoelectric sensors are available in various shapes and thread configurations to allow various types of measurements.

Integumentary Sensory Organs (ISOs) on the scale of crocodile allows them to hunt for prey in the dark by detecting the surface pressure waves and capable of vibration detection of up to 35Hz and response time of less than 100 milliseconds. Piezoelectric sensors mimics the function of ISOs by implementing quartz crystal into piezoelectric sensors. Quartz crystal has high response frequency ranging from 20Hz to 10kHz and microsecond of response time similarly to ISOs. By squeezing quartz crystals, electricity is generated and mechanical deformation of quartz crystal is measured by measuring the amount of electricity generated.


                                                   Figure 1 : Piezoelectric Construction 

In each cell of crystal has an electric dipole, and the cells are oriented such that the electric diploes are aligned. When a sufficient force is applied onto the crystals, deformation take place. The deformation disrupts the orientation of the electrical dipoles and create temporary excess of surface charge, which subsequently manifest voltage which is developed across the crystal.



Figure 2 : Electrical Dipoles in Quartz Crystal

To measure force or pressure using piezoelectric sensor, the surface charge on the crystal is measured. Two metal plates are used to sandwich the crystal making a capacitor. As mentioned above, an external force subjected to crystal causes deformation of crystal and resulting in a charge. A greater force will result in more surface charge as explain in Equation (1). The electrical charge from crystal is then converted into voltage and amount of force subjected can be measured.

V = Q/C

where ;

V = Voltage
Q = charge resulting from force
C = capacitance of device

When pressure is exerted onto 3D printed Dome, the crystal in piezoelectric sensors undergoes deformation, resulting in a charge. The charges is then converted into voltage that measures the dynamic pressure changes on the 3D printed Dome and detect 3D orientations.

Reflection

Yes, I do believe that our product would be functional and beneficial to the society if proper production took place. The fund necessary for research and manufacturing purpose can be funded through crowdfunding source. The trend of raising funds are now leaning towards crowdfunding which can be done through online. For example, we can propose and describe our usage of our product on a webpage and any anonymous or any interested individual towards our product can donate a certain amount of money to idealized our product. Ideas can be pitch to private companies that are involved in medical and aeronautical industry as it might be possible to help them cut their expenses in similar product.
In my opinion, many engineers seek solution from nature into their inventions and there is already numerous product in the market that utilizes nature. The most commonly found examples would be bullet train inspired by Kingfisher birds and antimicrobial film inspired by shark skin. Kingfisher birds have a specialized beak that allows them to dive into the water while causing minimal splash. Utilizing this feature, biomimicry was done to reduce the shock produced by the bullet train when entering tunnels. The shark on the other hand, has unique skin that are covered with dermal denticles that helps to reduce the drag experienced by the shark. This was applied on swimsuit technology to reduce the drag experienced by swimmers. The aqua industry is also utilizing this idea to air inhibit marine growth on the body of ships. Based on the same idea, hospitals are also producing a biomimetic sharkskin film to counter cross-contamination.

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