15 research outputs found
Quantification of Inter-Erythrocyte Forces with Ultra-High Frequency (410 MHz) Single Beam Acoustic Tweezer
No full textEfforts on quantitative measurements of the interactive forces of red blood cells (RBC) have been pursued for many years in hopes of a better understanding of hemodynamics and blood rheology. In this paper, we report an approach based on an ultra-high frequency (410 MHz) single beam acoustic tweezer (SBAT) for quantitative measurements of inter-RBC forces at a single cell level. The trapping forces produced by this ultra-high frequency (UHF) SBAT can be quantitatively estimated with a micropipette. Since the focal beam diameter of the 410 MHz ultrasonic transducer used in this SBAT was only 6.5 micrometer (mu m), which was smaller than that of a RBC (similar to 7.5 mu m), it was made possible to directly apply the beam to a single RBC and measure inter-RBC forces against the pre-calibrated acoustic trapping forces as another example of potential cellular applications of the SBAT. The magnitude of these forces was found to be 391.0 +/- 86.4 pN. Finally, it is worth noting that unlike several other methods, this method does not require the measuring device to be in contact with the cells.112sciescopu
Manipulation of levitated cell aggregates by high frequency acoustic trapping
No full textAcoustic tweezers can levitate and manipulate a single object or objects through air and water. Compared to other tweezer technologies: optical tweezers and magnetic tweezers, acoustic tweezers have a huge advantage on trapping larger objects and generating aggregates with strong trapping forces. Moreover, trapped samples are not required to be optically transparent or labeled with a magnetic bead. Recently, acoustic levitation technique appeared to be promising in targeted drug delivery in human body, thus many levitation methods using ultrasonic wave including standing wave and surface acoustic wave have been developed. The single beam acoustic trapping has a definitive advantage over other methods since it only employs a single transducer. In present study, we demonstrated that single beam acoustic tweezers (SBAT) can levitate red blood cells (RBCs) aggregation in three dimensions and successfully performed the manipulation of levitated cell aggregation. This study is a significant step forward in manipulation of cell aggregates using high frequency acoustic tweezers.1
Multifunctional single beam acoustic tweezer for non-invasive cell/organism manipulation and tissue imaging
No full textNon-contact precise manipulation of single microparticles, cells, and organisms has attracted considerable interest in biophysics and biomedical engineering. Similar to optical tweezers, acoustic tweezers have been proposed to be capable of manipulating microparticles and even cells. Although there have been concerted efforts to develop tools for non-contact manipulation, no alternative to complex, unifunctional tweezer has yet been found. Here we report a simple, low-cost, multifunctional single beam acoustic tweezer (SBAT) that is capable of manipulating an individual micrometer scale non-spherical cell at Rayleigh regime and even a single millimeter scale organism at Mie regime, and imaging tissue as well. We experimentally demonstrate that the SBAT with an ultralow f-number (f# = focal length/aperture size) could manipulate an individual red blood cell and a single 1.6 mm-diameter fertilized Zebrafish egg, respectively. Besides, in vitro rat aorta images were collected successfully at dynamic foci in which the lumen and the outer surface of the aorta could be clearly seen. With the ultralow f-number, the SBAT offers the combination of large acoustic radiation force and narrow beam width, leading to strong trapping and high-resolution imaging capabilities. These attributes enable the feasibility of using a single acoustic device to perform non-invasive multi-functions simultaneously for biomedical and biophysical applications.1111sciescopu
Evaluation method for acoustic trapping performance by tracking motion of trapped microparticle
No full textWe report a method to evaluate the performances of a single-beam acoustic tweezer using a high-frequency ultrasound transducer. The motion of a microparticle trapped by a 45-MHz single-element transducer was captured and analyzed to deduce the magnitude of trapping force. In the proposed method, the motion of a trapped microparticle was analyzed from a series of microscopy images to compute trapping force; thus, no additional equipment such as microfluidics is required. The method could be used to estimate the effective trapping force in an acoustic tweezer experiment to
assess cell membrane deformability by attaching a microbead to the surface of a cell and tracking the motion of the trapped bead, which is similar to a bead-based assay that uses optical tweezers. The results showed that the trapping force increased with increasing acoustic intensity and duty factor, but the force eventually reached a plateau at a higher acoustic intensity. They demonstrated that this method could be used as a simple tool to evaluate the performance and to optimize the operating conditions of acoustic tweezers.11sciescopu
Design of a high voltage 1 to 64 Mux/De-Mux for high frequency synthetic aperture imaging
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Calibration of trapping force on cell-size objects from ultrahigh-frequency single-beam acoustic tweezer
No full textIn this paper, we report a calibration of acoustic trapping force of single-beam acoustic tweezer (SBAT) at ultra-high frequency using micropipette aspiration. The acoustic trapping forces (F-trapping) and the trap stiffness on a 5-mu m polystyrene microbead for a 110-MHz SBAT were measured against the known force generated from a micropipette. The trap stiffness (k), which represents F-trapping corresponding to a displacement (x) of a microbead from the trap center, was measured and the results showed that a higher duty factor and excitation voltage lead to a stronger trapping force and trap stiffness for a given displacement. Since a precisely calibrated force generated from a micropipette is directly applied to the calculation of acoustic trapping force, the approach should be more flexible than those previously reported. In addition, with this method, precisely controlling the tip size of a micropipette within a few micrometers allows the possibility of calibrating the trapping force on an object of the size of a single cell. It not only helps better evaluate the trapping performance of SBAT as a tool of cell manipulation, but also helps develop SBAT as a useful tool for assessing cellular interactions.117sciescopu
Label-free analysis of the characteristics of a single cell trapped by acoustic tweezers
No full textSingle-cell analysis is essential to understand the physical and functional characteristics of cells. The basic knowledge of these characteristics is important to elucidate the unique features of various cells and causative factors of diseases and determine the most effective treatments for diseases. Recently, acoustic tweezers based on tightly focused ultrasound microbeam have attracted considerable attention owing to their capability to grab and separate a single cell from a heterogeneous cell sample and to measure its physical cell properties. However, the measurement cannot be performed while trapping the target cell, because the current method uses long ultrasound pulses for grabbing one cell and short pulses for interrogating the target cell. In this paper, we demonstrate that short ultrasound pulses can be used for generating acoustic trapping force comparable to that with long pulses by adjusting the pulse repetition frequency (PRF). This enables us to capture a single cell and measure its physical properties simultaneously. Furthermore, it is shown that short ultrasound pulses at a PRF of 167 kHz can trap and separate either one red blood cell or one prostate cancer cell and facilitate the simultaneous measurement of its integrated backscattering coefficient related to the cell size and mechanical properties.114sciescopu
