Photoacoustic Properties of Carbon Nanotubes-Polydimethylsiloxane
WU Ran-ran1, 2, XIA Hui2*, ZHANG Jing-jing1, XUN Li-na1*, SUN Zhi-shen3, LI Yuan-yuan2
1. School of Electrical Engineering and Automation, Anhui University，Hefei 230601，China
2. Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190，China
3. College of Information and Communication Engineering, Faculty of Information Technology, Beijing University of Technology，Beijing 100124，China
Abstract：Carbon nanotubes-polydimethylsiloxane (CNT-PDMS) is a new type of laser ultrasonic transducer （LIU-T）composite material with high frequency, wide width and high amplitude. The composite film can be used as an efficient and robust ultrasonic emitter for diagnosis and treatment. The intrinsic structure of nanocomposites provides unique thermal, optical and mechanical properties, which are not only conducive to energy conversion but also robust to pulsed laser ablation. PDMS polymers have high thermoelastic coefficients that allow materials to stretch and produce ultrasound. In this paper, the characteristics of photoacoustic signals produced by several kinds of composite films are studied, the photoacoustic signal characteristics under the different substrate and water boundary conditions were tested. Photoacoustic transducers made of carbon nanomaterials with high light absorption and PDMS polymers with high expansibility not only reduce the thickness of materials but also are expected to generate high frequency and high intensity ultrasonic signals. The thickness of the hard glass substrate realized in this paper is about 1mm, the thickness of the soft film substrate is at the micron level, and the thickness of water boundary conditions are 3 mm. Under pulsed laser excitation, the ultrasonic pressure at the end surfaces of water boundary conditions and hard glass substrates and soft film substrates was 2.0, 3.9 and 5.2 MPa, respectively. Through a series of studies, it is concluded that: (1) soft film substrate (3×3) has better negative pulse than hard glass substrate (3×3), which is more suitable for photoacoustic cavitation treatment; (2) water boundary conditions are not conducive to the generation of high-intensity photoacoustic signals. In a word, compared with piezoelectric transducers, laser-induced ultrasonic transducers have more potential to produce high- amplitude ultrasonic signals with a wide width and provide a new method of ultrasonic excitation without interference structures such as electronics, which is expected to be a new generation of laser ultrasonic transducers to replace piezoelectric transducers. The application of this new method in magneto-acoustic imaging can greatly reduce the interference of ultrasonic excitation sources. At the same time, compared with mixing CNT into PDMS, the method adopted in this experiment is more simple, convenient and material saving. For traditional hard glass substrate, the implementation of soft film substrate can produce high sound pressure 5.2 MPa, and center frequency in 5 MHZ, and -6 dB ultrasound is relatively close to 5 MHz wide bandwidth, compared with the 4.5 MPa pressure produced by the early implementation of CNT-PDMS Photoacoustic transducer in 2014, this paper implementation has more clinical application prospect, applied in Magneto-acoustic electric imaging etc. to avoid electromagnetic interference has the very good effect.
[1] Zhou Y, Ma Q Y, Guo G P, et al. IEEE Transactions on Biomedical Engineering, 2017, 65(5): 1086.
[2] le Jeune L, Robert S, Lopez Villaverde E, et al. Ultrasonics, 2016, 64: 128.
[3] Richard J Colchester, Charles A. Mosse Applied Physics Letters，2014，104：173502.
[4] Buma T, Spisar M, O’Donnell M. Appl. Phys. Lett.，2001, 79：548.
[5] Colchester R J, Mosse C A, Bhachu D S, et al. Appl. Phys. Lett., 2014, 104: 173502.
[6] Hsieh B Y, Kim J, Zhu J, et al. Appl. Phys. Lett.，2015, 106：021902.
[7] Chang W Y, Huang W B, Kim J, et al. Appl. Phys. Lett.，2015, 107：161903.
[8] Lee S H, Park M A, Yoh J J, et al. Appl. Phys. Lett.，2012, 101：241909.
[9] Yang H, Kim J S, Ashkenazi S, et al. Appl. Phys. Lett., 2006, 89: 093901.
[10] Baac H W, Lee T, Ok J G, et al. Appl. Phys. Lett., 2013, 103: 234103.
[11] Lee Taehwa, Baac Hyoung Won, Li Q C, et al. Optical Mater，2018, 6: 1800491.
[12] Chen Zeyu, Wu Yue. Nano Energy，2018，46：314.
[13] Huang W B, Chang W Y，Kim J, et al. IEEE Transactions on Nanotechnology, 2016, 15(3): 395.
[14] Hindley J, Gedroyc W M, Regan L, et al. American Journal of Roentgenology, 2004, 183：1713.
[15] Hou Y, Ashkenazi S, Huang S W, et al. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2007, 54(3): 682.
