Design And Fabrication Of A Miniature Broadband Vibration Transducer Based On The Sierpinski Fractal Structure

With the rapid development of microelectronic devices in recent years, the problem that how to supply its network node efficiently has become a new hotspot. In order to overcome the problems existing in variety of micro-electronic devices caused by the conventional battery and power cable, the self-powered technology that collecting ambient energy spontaneously is raising more and more attention. The vibration transducer is a power generation device acquiring vibration energy in the environment into electrical energy spontaneously. Problems of narrow frequency response bandwidth, unstable energy conversion and low conversion efficiency occurs in the traditional vibration transducer universally. The piezoelectric vibrator based on fractal structural,combined with characteristics of the self-similarity and structural diversity to increases the energy density and broaden the bandwidth of frequency response, was proposed to solve the above-mentioned problems in this paper.A small piezoelectric oscillator structure with broadband based on Sierpinski fractal was designed in this thesis. Three different levels of unit structure was designed through reforming the Sierpinski triangle with the principle of cantilever beam. Different unit structures corresponds different resonant frequencies, being capable of responding to vibration mechanical energy of different frequencies from the environment and thereby increasing the bandwidth of the piezoelectric transducer. The size of the unit structure was Fine-tuned, avoiding the connection between internal small units. The internal nodes in the designing structure was fixed to ensure the stability of the piezoelectric oscillator.The piezoelectric vibration transducer device based on fractal structure was fabricated with polyvinylidene fluoride piezoelectric material with coating aluminum film on its surface. The piezoelectric film was cut precisely to process out the designing structure.The size of 50 mm × 50 mm piezoelectric vibration transducer device was finally manufactured with leading a couple of wires after reinforcement with a conductive copper frame and the encapsulation procedure of installing the plexiglass protective layer effectively.The fractal piezoelectric transducer device was also tested. The frequency response spectroscopy, periodically sweeping and the relationship test between the intensity vibration source and the output voltage were carried out and results were in a good agreement with our anticipation. Therefore, the piezoelectric transducer based on Sierpinski fractal structure designed in this thesis showed the characteristic of broadband and energy conversion stability, having a wide bandwidth of energy conversion with its smaller volume.