Research On Laser-induced Damage Threshold Characteristics Of Optoacoustic Transducer Based On CNT-PDMS

Ultrasound is widely used in clinical medicine due to its real-time dynamics,non-inva-sive safety and other characteristics.Generally,the core component of ultrasonic medical treatment,the ultrasonic transducer,is an electric drive device based on the piezoelectric effect,which is vulnerable to electromagnetic interference.The photoacoustic effect-based optoacoustic transducer has gradually attracted people’s attention due to its simple prepara-tion process and electromagnetic compatibility,and has the potential to be applied in the fields of thrombolysis,nerve stimulation,and drug delivery.Therefore,the research on opto-acoustic transducers is of great significance.The core of the optoacoustic transducer is the photoacoustic composite material composed of light-absorbing materials and thermal expan-sion materials.The light-absorbing material completes light-heat conversion through a non-radiative transition mechanism.The thermal expansion material generates mechanical vibra-tions based on the principle of thermal expansion and contraction to emit ultrasonic waves.In the photo-thermal conversion process,when the laser energy density is too high,the ther-mal performance of the composite material will be deteriorated,which will cause laser-in-duced damage to the optoacoustic transducer.This severely limits the service life of the opto-acoustic transducer and affects its application in ultrasound therapy.However,there are few reports on the laser-induced damage threshold theory of optoacoustic transducers and its in-fluencing factors.Therefore,this article has thoroughly studied the laser-induced damage threshold characteristics of the optoacoustic transducer.First,based on the thermal ablation damage theory,the laser-induced damage threshold theoretical model of the CNT-PDMS optoacoustic transducer is established.Then,according to the theoretical model,the effects of thermal diffusivity and concentration of the light-ab-sorbing material and the thickness of the photoacoustic composite material on the laser-in-duced damage threshold are studied.The experimental results are consistent with the theory,and the laser-induced damage threshold(F_th)of the optoacoustic transducer can be calculated more accurately.When the laser energy density is less than 0.8F_th,the optoacoustic trans-ducer can work stably for a long time.Secondly,a high thermal expansion coefficient and thermal stability polydimethylsiloxane（PDMS）is used as the thermal expansion material to prepare a self-healing optoacoustic transducer with high laser-induced damage threshold.The transducer can not only heal itself after damage,but also has good acoustic performance.Its laser-induced damage threshold is greater than 152.87 m J/cm²,the sound pressure is higher than 30 MPa,the center frequency is 8.3 MHz,and the photoacoustic conversion efficiency is as high as 1.07×10^-2.Finally,using the high intensity ultrasound generated by the self-healing optoacoustic transducer,the manipulation of the particles is realized,which proves that the device has the potential application in drug delivery.