Study On Laser Ultrasound Transducers Based On PDMS-Carbon-Based Composites

Ultrasound is widely used in non-destructive testing and medical ultrasound.Current ultrasonic transducers are usually based on piezoelectric ceramics,which have a narrow band that affects the resolution of imaging.In addition,the vulnerability of piezoelectric materials and the impedance mismatch of large aperture make the application of highfrequency ultrasound in precision treatment also face challenges.Laser ultrasound transducer is an effective method to solve these problems.The Laser-generated ultrasound method based on photoacoustic effect can produce ultrasonic signals with very short duration and wide frequency band,and the laser ultrasound source can be used in harsh environments such as high temperature,high pressure,poison and radioactivity.High efficiency laser ultrasound transducers can significantly increase the sound pressure,effectively improve the depth of ultrasonic penetration,and even provide useful thermal and mechanical effects on the tissue.In the field of non-destructive testing,The Lasergenerated ultrasound method can generate ultrasonic waves through flexible materials and can be directly attached to complex curved surfaces,which avoids the need to make special ultrasonic probes for specific curved surfaces and can effectively reduce the cost of non-destructive testing and improve the accuracy of testing.In this paper,the research status and principle of laser ultrasound transducers at home and abroad are introduced in detail.Based on the principle of Laser-generated ultrasound,the Multiphysics finite element analysis software COMSOL was used to simulate the laser ultrasound transducer of polydimethylsiloxane(PDMS)-Carbon-Based composites,and the heat diffusion process of the transducer was analyzed with the solid heat transfer mode.The stress and strain distribution of transducer is analyzed by solid mechanics mode.Finally,the sound field in water medium is simulated based on acoustic mode and sound solid coupling.The effects of material thickness,thermal penetration depth and pulsed laser parameters on the sound field performance in the medium were studied.In-depth study of candle soot nanoparticles,carbon black,multiwalled carbon nanotubes-PDMS composites,the results show that as a light absorbing material,candle soot nanoparticles are better than carbon black and multiwalled carbon nanotubes,multiwalled carbon nanotubes are better than carbon black.The experimental results show that large negative ultrasound pressure can be obtained and the size of laser ultrasound transducer can be effectively reduced.Based on the laser ultrasound transducer,a new type of integrated Laser-generated ultrasound-piezoelectric transducer is presented.The material selection of the laser ultrasound transducer and piezoelectric transducer,the structure design of the laser-generated ultrasound-piezoelectric transducer,and the design and fabrication of the piezoelectric transducer are completed.Laser-generated ultrasound-piezoelectric transducer adopts a front-rear structure,and the piezoelectric transducer working area can receive ultrasonic waves on both sides.The results prove that the piezoelectric transducer does not affect the frequency of the transmitted acoustic wave and can accept the acoustic wave of the laser ultrasound transducer and the acoustic wave reflected back by the aluminum block through the piezoelectric transducer.A new type of integrated Lasergenerated ultrasound-piezoelectric transducer is used to carry out c-scan imaging on the 3D printed parts and one dollar.