Annular Array Search Units and Their Potential Application in Conventional Ultrasonic Testing Systems
This paper is based on a program to investigate the potential of multi-element annular arrays for practical application in ultrasonic testing systems. The annular array is comprised of coaxially-located, ring-shaped piezoelectric elements. By providing excitation pulses in a spherical time relationship, the transmitted beam may be focused at a specific range. By electronic switching, the focal point can be placed at various distances in the material under examination, Of particular interest is the length over which the beam can be held in collimation. Fabrication methods, delayed excitation techniques, and beam patterns in water and steel are described,
A New Ultrasound Imaging Technique Employing Two-Dimensional Electronic Beam Steering
In recent years, ultrasound imaging based on B-mode echosonography has become an accepted and useful technique in medical diagnosis. However, the application of this technique has been limited by the time required to obtain an adequate image, the resolution that can be obtained in the image and problems related to the dynamic range of the echo information. A new ultrasound imaging system which removes or substantially reduces many of these limitations has been developed in the hope that ultrasound tomography may find even more widespread application and greater diagnostic value.
Engineering bio-inks for 3D bioprinting cell mechanical microenvironment
Three-dimensional (3D) bioprinting has become a promising approach to construct­ing functional biomimetic tissues for tissue engineering and regenerative medicine. In 3D bioprinting, bio-inks are essential for the construction of cell microenviron­ment, thus affecting the biomimetic design and regenerative efficiency. Mechanical properties are one of the essential aspects of microenvironment, which can be char­acterized by matrix stiffness, viscoelasticity, topography, and dynamic mechanical stimulation. With the recent advances in functional biomaterials, various engineered bio-inks have realized the possibility of engineering cell mechanical microenviron­ment in vivo. In this review, we summarize the critical mechanical cues of cell micro­environments, review the engineered bio-inks while focusing on the selection princi­ples for constructing cell mechanical microenvironments, and discuss the challenges facing this field and the possible solutions for them.