A novel CNTs array-PDMS composite with anisotropic thermal conductivity for optoacoustic transducer applications

As a promising ultrasound device, the optoacoustic transducer whose core part is an organic/inorganic composite, causes much attention and creates new opportunities. Unfortunately, how to control its operational frequency is still an open question. Here, taking the advantage of an aligned carbon nanotubes (CNTs) array-polydimethylsiloxane (PDMS) composite with anisotropic thermal conductivity, we introduce a novel optoacoustic transducer. Based on an advanced inductively coupled plasma (ICP) etching technology, the composite's thickness can be reduced from 200 μm to 18 μm. When its thickness is approximately 18 μm, high frequency (>20 MHz) laser-generated ultrasound can be obtained. It is demonstrated experimentally and theoretically that the transducer's operational frequency is reverse proportion to the thickness of CNTs array-PDMS composite, which can confirm that this optoacoustic transducer works in thickness mode. Furthermore, this kind of device can be miniaturized and amounted on tip of an optical fiber to realize all optical high frequency ultrasound imaging. All these encouraging results suggest that this novel CNTs array-PDMS composite may provide an effective path for the frequency control of the optoacoustic transducer and this obtained device has the potential to be used for biomedical ultrasound applications in the future.