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Many high-end power machines demand greater bearing performance in terms of running speed, precision, reliability, longevity, noise reduction, etc. An ultrasonic bearing based on Near-Field Acoustic Levitation (NFAL) effect is a kind of emerging noncontact gas bearing. Due to its self-aligning capability, the ultrasonic bearing can steadily run at a high speed under high precision. Actuated by piezoelectric...
Cardiovascular disease, including atherosclerosis and critical limb ischemia, affects millions of people worldwide. There is a clinical need to base treatment decisions on quantitative analysis of the plaque composition. However, no reliable clinical methods to quantify the mechanical properties of plaque components and detect plaque vulnerability currently exist, particularly for coronary disease...
Elastic properties of the ocular tissues are significantly affected by intraocular pressure (IOP) in the eye. For example, the speed of the elastic wave in the cornea dramatically increases with IOP. In our previous studies using ultrasound shear wave imaging we demonstrated that, for the lens, the increase in IOP does not result significant changes in the wave velocity. Compared with ultrasound imaging,...
Piezoelectric ultrasonic motors (PUMs) are based on the concept of driving the runner by a mechanical vibration excited on the stator via the converse piezoelectric effect. They exhibit merits of small size, simple structure, quick response, high accuracy and resolution, self-locking when power off and a lack of electromagnetic radiation. The linear PUMs become the research focus in recent years as...
Displacement estimation is a critical component of elastography. The measurement of sub-resolution displacements relies on high cross-correlation (CC) between repeated collinear RF acquisitions. CCs are degraded by common sources of acoustic noise, such as reverberation clutter, in addition to the displacement of scatterers within the radiation force field. CCs are also degraded spatially across the...
Blood clotting, a process to avoid bleeding, involves vasoconstriction, platelet plug build-up, coagulation, clot retraction and fibrinolysis. During coagulation, blood changes from liquid to gel, and the clot viscoelastic properties continue modifying until fibrinolysis. Tests to analyze bleeding disorders and anticoagulant therapy include clot-based assays, to detect the end-point of fibrin network...
Ultrasound-mediated drug delivery using microbubbles is a growing field with applications ranging from targeted chemotherapy to permeating the blood brain barrier. Despite the potential clinical impact of this technique, the precise parameters needed to reliably induce cell sonoporation, or increased cellular permeability, are not well understood. The goal of this work is to use high frame rate imaging...
To elicit bio-effects, ultrasound (US) stimulated microbubbles (MBs) must be in proximity to their target and this is not always the case (e.g. sonothrombolysis). Radiation forces can direct MBs to clots and our previous work suggested clot degradation patterns (Fig A) could be influenced by ‘transport pulses’. However, this is a complex process involving a population of MBs, with size-dependent radiation...
A U-shaped linear piezoelectric ultrasonic motor (PUM) was proposed, designed and tested in this work, in which three longitudinal transducers were used together to achieve the linear driving by two feet synchronously. Longitudinal vibrations of the transducers were generated with certain temporal shift to form the desired elliptical movements on the two driving feet. Finite element method (FEM) was...
The acoustic microstreaming originating from microbubbles' linear oscillations can be used as a potential cell sonoporation tool for drug delivery and gene transfection. However, this bubble-based method suffers from bubble instability, non-uniform size, unreliable performance, and inconvenient trapping. In order to overcome the above drawbacks, in this study, we proposed a massive drug delivery method...
Streaming velocity mainly depends on the intensity and absorption of ultrasound in the media. For high frequencies exceeding 20 MHz the speed of streaming in blood is also affected by scattering effects on the blood cells and contrast agent microbubbles. According to theoretical calculations, 12.2 % increase in streaming velocity for 1 g/l starch concentration rise should be expected. The theory has...
Flow cytometer plays an important role in cell sorting and analysis. Traditional flow cytometers adopt hydrodynamic focusing method which works well when the low flow velocity is relatively low. However, in order to have a higher analysis efficiency for clinical laboratories, a higher flow velocity is preferred, which sometimes will lead to cells siltation when using sheath flow. In this paper, an...
The concept of the band structure is central to the field of phononic crystals. Indeed, capturing the dispersion of Bloch waves — the eigenmodes of propagation in periodic media — gives invaluable information on allowed propagation modes, their phase and group velocities, local resonances, and band gaps. Band structures are usually obtained by solving an eigenvalue problem defined on a closed and...
The 30MHz lithium niobate (LiNbO3) ultrasound transducer with a highly focused beam was used to generate gradient force which can pull a single leukemia cell to toward a focus to be a trapping situation. The transducer was sterilized by using 70% ethanol before the experiment. Five leukemia cells before treatment and five cells after treatment by a chemotherapy drug were trapped and measured their...
Myocardial elastance, derived from pressure-volume (PV) loops in the left ventricle (LV), can be used to assess LV function and myocardial performance. This method requires an invasive intracardiac pressure-volume catheter to be inserted in the LV, limiting the method's utility in clinical screening and monitoring. Strain echocardiography and cardiac acoustic radiation force impulse (ARFI) imaging...
It was shown experimentally in [1] that a macroscopic cylindrical solid can be rotated due to the excitation of two counter-propagating surface acoustic waves (SAWs) with different amplitudes on its surface. The arising distributed rotation force has been estimated phenomenologically in the partial case of a piezoelectric tube with a ring unidirectional electrode transducer (RUDT) using the torsion...
Nanoparticle manipulation has a variety of potential applications, from two-dimensional material fabrication to biomedical engineering. Pattern and transportation of nanoparticles has been receiving increasing attention in recent years. Ultrasound as a mechanical wave has proven to be the most effective in the manipulation of micro-objects in a non-contact and non-invasive fashion. However, due to...
A method for measurement of the bladder wall nonlinear elasticity is presented. The method is based on acoustoelasticity modeling of the bladder tissue modulus of elasticity changes at different volumetric loading levels. At each loading volume, tissue strain is obtained from the real-time images. Using acoustic radiation force, a transient Lamb wave is excited on the bladder wall and shear elasticity...
The pathological or physiological changes of the crystalline lens directly affect the eye accommodation and transmittance, and then increase the risk of the presbyopia and cataract for people in middle and old age groups. There is no universally accepted quantitative method to measure the lens' mechanical properties in vivo so far. This study aims to investigate the possibility of assessing the age-related...
A real-time ultrasound (US) coagulation monitoring for coagulation based on acoustic radiation force is described. US imaging to facilitate HIFU has advantages with respect to portability, cost effectiveness and spatiotemporal resolution. Localized motion imaging (LMI) is one of the techniques based on US to detect a change of tissue mechanical properties caused by its thermal coagulation. To achieve...
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