Integrated ultrasonic particle positioning and low excitation light fluorescence imaging

A compact hybrid system has been developed to position and detect fluorescent micro-particles by combining a Single Photon Avalanche Diode (SPAD) imager with an acoustic manipulator. The detector comprises a SPAD array, light-emitting diode (LED), lenses, and optical filters. The acoustic device is formed of multiple transducers surrounding an octagonal cavity. By stimulating pairs of transducers simultaneously, an acoustic landscape is created causing fluorescent micro-particles to agglomerate into lines. The fluorescent pattern is excited by a low power LED and detected by the SPAD imager. Our technique combines particle manipulation and visualization in a compact, low power, portable setup

Acoustic tweezing at the nodes or antinodes of a heptagonal multi piezoelectric transducer cell

We present a novel device for acoustically manipulating or sonotweezing micron-scale elements. Such techniques, that allow the micro-manipulation of cells, particles or droplets by non-invasive means, are desired to facilitate biophysical or biological applications such as microarrays and tissue engineering. Non-invasive techniques exploiting the acoustic radiation force have been demonstrated for trapping, separating and moving particles. Most results to date describe acoustic trapping using geometrically fixed standing wave patterns. However, the concerted action of multiple transducers can be used to generate electronically controlled standing wave patterns. This paper investigates 2-D particle micro-manipulation in a closed system using two or three transducers. In such systems, wave reflections can be detrimental to performance hence the geometry of the device has a strong impact on the quality of the particle trapping and this is discussed. We will also demonstrate that acoustic trapping can occur at the nodes or antinodes depending on the properties of the particle suspended in the medium

Terahertz free space communication based on acoustic optical modulation and heterodyne detection

A terahertz free space communication system based on acoustic optical modulation and heterodyne detection is demonstrated. A high resistivity silicon acoustic optical modulator was used to modulate a continuous terahertz wave at 2.52 THz. A pyroelectric detector was used to detect the modulated terahertz signal via heterodyne detection mode. A modulation frequency of 937 kHz and sampling rate of 1 kbit/s was achieved

Direct patterning of mammalian cells in an ultrasonic heptagon stencil

We describe the construction of a ultrasonic device suitable for micro patterning particles and cells for tissue engineering applications. The device is formed by seven transducers shaped into a heptagon cavity. By exciting two and three transducers simultaneously, lines or hexagonal shapes can be formed with beads and cells. Furthermore, phase control of the transducers allows shifting the standing waves and thus patterning at different positions on a surface in a controlled manner. The paper discusses direct patterning of mammalian cells by ultrasound “stencil”

Controlling acoustic streaming in an ultrasonic heptagonal tweezers with application to cell manipulation

Acoustic radiation force has been demonstrated as a method for manipulating micron-scale particles, but is frequently affected by unwanted streaming. In this paper the streaming in a multi-transducer quasi-standing wave acoustic particle manipulation device is assessed, and found to be dominated by a form of Eckart streaming. The experimentally observed streaming takes the form of two main vortices that have their highest velocity in the region where the standing wave is established. A finite element model is developed that agrees well with experimental results, and shows that the Reynolds stresses that give rise to the fluid motion are strongest in the high velocity region. A technical solution to reduce the streaming is explored that entails the introduction of a biocompatible agar gel layer at the bottom of the chamber so as to reduce the fluid depth and volume. By this means, we reduce the region of fluid that experiences the Reynolds stresses; the viscous drag per unit volume of fluid is also increased. Particle Image Velocimetry data is used to observe the streaming as a function of agar-modified cavity depth. It was found that, in an optimised structure, Eckart streaming could be reduced to negligible levels so that we could make a sonotweezers device with a large working area of up to 13 mm × 13 mm

Transducer Design for Dexterous Sonotweezers

No abstract available

Transducer Design for Dexterous Sonotweezers

No abstract available

Functional Characterisation of High Frequency Arrays Based on Micro-moulded 1–3 Piezocomposites

A clinical need exists for high frequency ultrasound arrays that can provide improved image quality compared to the single-element transducers currently used in real-time high resolution imaging systems. Miniature arrays based on fine-scale piezocomposites are required for sufficiently sensitive imaging systems. In this paper we report fabrication and functional characterization of prototype linear arrays suitable for high frequency imaging. Array electrodes have been patterned photolithographically on the surface of micro-moulded 1–3 piezocomposites with processes than can be scaled for linear arrays operating at 100 MHz. Functional testing of arrays with 50 µm and 15 µm pitch demonstrates feasibility of this approach