Ultrasonic waves are used in different engineering and biological applications. They are used to diagnose, eva‎luate and perform a process. In some cases, it is necessary to focus ultrasound waves in a specific area to use the heat or shocks generated in the area to make changes. Focusing of ultrasound waves is possible by using concave piezoelectric or by using a lens in the path of waves emitted from a flat piezoelectric. In this research, due to the economic reasons and flexibility of the method, a lens was used to focus the waves. The intensity in the focal area of HIFU transducers is determined by the ratio of the focal length of the transducer to its aperture diameter. This ratio has an inverse relationship with the generated intensity in the focal area. In this research, two lenses with different focal lengths and curvature radii, and the same aperture diameter were designed and fabricated to focus ultrasound waves. Then, the equipment for installation of the focused ultrasound transducer, the polymer solution chamber, and the nanofiber collector mechanism were designed and fabricated. In this system, in order to obtain flexibility in the characteristics of the produced nanofibers, it is possible to install different lenses to focus ultrasound waves with different intensities and quickly adjust the height of the nanofiber collector plate from the surface of the polymer solution. In order to make the electrospinning process possible, the ability of controlling pulse repetition frequency (PRF) and duty cycle have been also added to the control unit. A hydrophone was designed and manufactured to determine the focal area of the fabricated transducers. In order to obtain the output pulses of the hydrophone, it is connected to an oscilloscope and the voltage of different areas of the transducers is recorded. The focal lengths for the transducers are 19.7 and 32.2 mm. Finally the Taylor cone, which is necessary for the initiation of electrospinning process was created on the surface of the polymer solution and the electrospinnig of polyvinyl alcohol nanofibers was started.

عليرضا فدائي تهراني , امين اله محمدي

مهدي كاروان

محسن بدرسماي , محمد دانش