WO2019119368A1

WO2019119368A1 - Acoustically driven flow-type cell detection apparatus

Info

Publication number: WO2019119368A1
Application number: PCT/CN2017/117833
Authority: WO
Inventors: 郑海荣; 李飞; 蔡飞燕; 许迪; 夏向向; 林勤; 孟龙; 肖杨; 邱维宝; 李永川; 苏敏; 黄继卿
Original assignee: 深圳先进技术研究院
Priority date: 2017-12-21
Filing date: 2017-12-21
Publication date: 2019-06-27

Abstract

An acoustically driven flow-type cell detection apparatus, comprising a cell manipulation module (10), an imaging module (20) and an image processing module (30), wherein the cell manipulation module (10) comprises a flow chamber and an ultrasonic radiation force generation system, and the ultrasonic radiation force generation system is used for generating an acoustic radiation force on cell particles, and manipulating the cell particles to be arranged in parallel lines, thereby achieving multi-row focusing, suspending the cell particles, and driving the cell particles to be transported in an oriented manner to a detection area so as to achieve multi-channel parallel detection. The detection apparatus uses an acoustic radiation force to manipulate cell particles so as to achieve transportation and focusing, and therefore, no complicated pump system is required to drive and control a fluid, and a sheath fluid does not need to be introduced. The detection apparatus uses a virtual channel formed by the acoustic radiation force to arrange cells, thereby avoiding the problem of a cavity being blocked. The acoustic radiation force can arrange multiple rows of cells, and therefore, multi-channel parallel processing of multi-row focusing is achieved. The flow chamber has low costs and can be changed each time, and therefore, the problem of a residue in a flow channel contaminating a new sample is avoided.

Description

Acoustic driven flow cytometry device

Technical field

The present application relates to a flow cytometry device, and more particularly to an acoustically driven flow cytometry device.

Background technique

A flow cytometer is a device that automatically analyzes and sorts cells. Flow chambers and flow drive systems are key components of flow cytometry. The flow chamber is composed of a sample tube, a sheath liquid tube and a nozzle. It is usually made of transparent and stable materials such as optical glass and quartz. The design and production are very fine, and it is the core of the liquid flow system. The sample tube stores the sample, and the single cell suspension is ejected from the sample tube under the pressure of the liquid flow; the sheath liquid flows from the periphery to the orifice through the sheath tube, and the envelope 1 is ejected from the nozzle after the outer circumference of the sample. Due to the action of the sheath fluid, the cells to be detected are confined to the axis of the flow.

Therefore, the current flow cytometry mainly uses water flow force to realize the transport and flow focusing of cell particles in the microfluidic channel. The technical solution mainly has the following problems: the suspended particles are easy to block the microcavity, and the cost of replacing the channel is relatively high. High; flow-focusing experiments require expensive sheath-constrained cells to be arranged in a single column; complex and expensive microfluidic pump systems are required to drive fluid flow; current flow cytometry is primarily single-channel processing rather than multi-channel parallel processing Way; difficult to clean, residual samples in the flow channel will pollute new samples.

Current flow cytometry primarily utilizes water flow forces to achieve cell awaiting detection of transport and flow focusing of particles within the microfluidic channel. In order to make the fluid flow, the air compression pump is usually used to compress the air to provide the necessary pressure for the fluid flow, and the pressure regulator stabilizes the flow pressure to form a constant flow, so that the sample particles can flow into the flow chamber at a constant speed. However, the gas path and control method involved in such a pump system is complicated, requires many components, and is bulky in system assembly.

Flow focusing is a key module of flow cytometry. It usually uses sheath flow focusing to form a package extrusion effect on the sample stream. The sample stream is focused at the center of the channel, and the cell particles in the sample stream are linearly arranged. Thereby, the cell particles are passed through the detection zone one by one. The introduction of the sheath fluid by this method increases the amount of introduction of the entire liquid, increases the complexity of the entire flow control system, and the sheath fluid is also an expensive consumable.

The other method does not require the use of a sheath fluid, and the cells are focused by externally applied field forces or fluid forces in the channel, allowing the cells to pass through the detection zone one by one. The patent "a microfluidic chip and its preparation method and application" (application No. 201611146452.6) and "a particle sorting method and its apparatus and use" (application number 201710016125.7) use the external standing wave sound field to arrange the cell particles into one Or multiple lines to achieve single-column or multi-column focusing so that cells pass through the detection area one by one. It has also been reported in the literature to focus the cell particles by the fluid forces such as the recirculation force after fluid separation, the fluid inertia lift and the vortex effect force, and the inertial Dean flow lift. Although this method does not require the introduction of an applied force field, it requires precise control of the liquid, increasing the complexity of the system. The patent of the publication No. US2009/0042241A1 employs a shrink-type sheath-free flow-cell particle focusing method, but its fluid passage is extremely easily blocked by large particles. In addition, these methods still require complex pumping systems to power liquid transport cells.

Most current flow cytometers are single-channel focusing methods. In order to improve throughput, multi-channel parallel processing flow cytometry has also been reported in the patent literature. The patent "a microfluidic chip and its preparation method and application" (application No. 201611146452.6) uses a standing wave field generated by a plurality of transducers to arrange cells into a plurality of lines, thereby realizing multi-column focusing and parallel processing. Patented "System and Method for Measuring Multiple Emissions from Multiple Parallel Flow Channels in a Flow Cytometry System" (Application No. 201080027480.0) discloses a flow cytometry system with multiple parallel flow channels to enhance The system detects the number of cells per second.

There are three main disadvantages in the prior art:

Both need to use a complex pump system to drive the fluid, and the flow drive system costs more;

The transport, focusing and detection of the particles need to be carried out in single or multiple microchannels. The suspended cell particles in the flow channel are easy to block the channel, the system is ineffective, and the replacement cost is high;

It is not easy to clean, and residual samples in the flow chamber and liquid system can contaminate new samples.

Summary of the invention

The technical problem to be solved by the present application is to provide an acoustically driven flow cytometry apparatus for the deficiencies of the prior art.

The technical problem to be solved by the present application is solved by the following technical solutions:

An acoustically driven flow cytometry apparatus comprising a cell manipulation module for manipulating cell particles in a sample solution, and an image processing module for smearing the stained cell particles Fluorescence imaging is performed, the image processing module is for processing and analyzing a fluorescent image, counting cell particles and estimating cell particle size, the cell manipulation module comprising a flow chamber and an ultrasonic radiation force generating system, the flow chamber for a sample solution containing cell particles; the ultrasonic radiation force generating system is used to generate acoustic radiation force on the cell particles, and the control cell particles are arranged in parallel lines to achieve multi-line focusing, suspending the cell particles, and driving the cell particles to be oriented and transported. Multi-channel parallel detection is achieved to the detection area.

The ultrasonic radiation force generation system includes a radiation force generation mechanism, a signal generator, and a power amplifier. After the electrical signal generated by the signal generator is amplified by the power amplifier, the excitation radiation force generating mechanism generates ultrasonic waves and further generates radiation to the particles. Force to achieve transport and manipulation of cells.

The flow cell includes a substrate, a PDMS sidewall and a glass cap, the PDMS sidewalls being bonded to the substrate and the glass cap, respectively, the substrate being made of quartz glass, plexiglass or silicon.

The radiation force generating mechanism includes an ultrasonic transducer and an artificial structure placed in the flow chamber, and an electrical signal amplified by the power amplifier excites the ultrasonic transducer to generate ultrasonic waves and thereby generate a radiation force to the particles.

The artificial structure includes an artificial periodic structure or an artificial aperiodic structure.

The artificial periodic structure includes a substrate and a plurality of ridges disposed on a lower surface of the substrate, the ridges being disposed in parallel and equally spaced.

The ultrasonic transducer is disposed outside the flow chamber, and the ultrasonic transducer does not coincide with a geometric center of the artificial periodic structure.

The radiation force generating mechanism includes a plurality of transducers placed outside the flow chamber for synthesizing the sound field

Device.

The plurality of transducers includes at least one ultrasonic transducer and interdigitated transducers disposed in pairs and arranged in parallel, the interdigital transducers being used to synthesize a standing wave field aligning cells to achieve focusing, the ultrasonic transduction The device is used to generate a biased Gaussian beam to transport cells.

Due to the adoption of the above technical solutions, the beneficial effects of the present application are as follows:

In a specific embodiment of the present application, the cell manipulation module includes a flow chamber and an ultrasonic radiation force generation system for containing a cell manipulation module, an imaging module, and an image processing module, and the flow chamber is for holding a sample solution containing cell particles; The force generation system is used to generate acoustic radiation force on the cell particles, and the control cell particles are arranged in parallel lines to achieve multi-line focusing, suspending the cell particles, and driving the cell particles to be transported to the detection area to achieve multi-channel parallel detection. Since the present application utilizes acoustic radiation force to manipulate cell particles for transport and focusing, there is no need for a complicated pump system to drive the control fluid, nor to introduce a sheath fluid; since the present application utilizes a virtual channel composed of acoustic radiation forces to align cells, it does not need to be present. There are microchannels used in the technology, thus avoiding the problem of clogging of the channel; multi-row parallel processing is realized by multi-line focusing due to the arrangement of multiple rows of cells due to acoustic radiation force; due to the cell manipulation module in the present application The components such as the flow chamber are low in cost and simple in process, and can be replaced with new devices each time a new sample is measured, thereby avoiding the problem of contamination of the new sample by the residue in the flow channel in the prior art. In summary, the present application provides a flow-free cell detection solution without microfluidic channels, no microfluidic pumps, no sheath fluid, disposable, parallel processing, and low cost.

DRAWINGS

1 is a schematic diagram of functional modules of an apparatus of the present application in an embodiment;

2 is a schematic structural view of an artificial cycle structure of the present application in an embodiment;

Figure 3 is a transmission spectrum of the artificial periodic structure shown in Figure 2;

Figure 4 is a distribution of the artificial sound structure modulating the sound field along the x direction;

Figure 5 shows the acoustic radiation force of the cells in the three directions of x, y, and z in the artificial structure sound field;

6 is a sound pressure field distribution and a direction of radiation force components Fy and Fz when the artificial periodic structure resonates in the yz plane;

Figure 7 is a distribution of the radiation force components Fy and Fz in the y direction when the artificial periodic structure resonates in the yz plane;

Figure 8 is a view showing the distribution of the sound pressure field and the directions of the radiation force components Fy and Fz when the artificial periodic structure in the yz plane is non-resonant;

Figure 9 is a distribution of sound pressure field and distribution of radiation force components Fy and Fz along the y direction when the artificial periodic structure in the yz plane is non-resonant;

Figure 10 is a distribution of acoustic radiation force components Fx and Fz along the transport direction x;

Figure 11 is an image acquired using the acoustically driven flow cytometry apparatus of the present application;

FIG. 12 is a schematic structural view of a radiation force generating mechanism of the present application in an embodiment.

Detailed ways

The present application will be further described in detail below with reference to the accompanying drawings.

Embodiment 1:

As shown in FIG. 1, an embodiment of the acoustically driven flow cytometry apparatus of the present application includes a cell manipulation module 10, an imaging module 20, and an image processing module 30. The cell manipulation module 10 is for manipulating the cell particles in the sample solution, the imaging module 20 is for fluorescence imaging of the stained cell particles, the image processing module 30 is for processing and analyzing the fluorescence image, counting the cell particles and estimating the cell particle size. . The cell manipulation module 10 can include a flow chamber and an ultrasonic radiation force generating system, and the flow chamber can be a microcavity for holding a sample solution containing cell particles. Ultrasonic radiation force generation system is used to generate acoustic radiation force on cell particles, manipulate cell particles to be arranged in parallel lines, achieve multi-line focusing, suspend cell particles, and drive cell particles to be transported to the detection area to achieve multi-channel parallel detection.

Imaging module 20 can include a fluorescent excitation source, an optical lens, a highly sensitive fluorescent camera. The image processing module 30 can include a computer, a high speed data acquisition card, hardware control software, and image acquisition analysis processing software for processing and analyzing the fluorescent image, counting the cells, and estimating the cell size. The focus and transport of the cells are mainly achieved by the radiation force generated by the ultrasonic radiation force generating system.

In one embodiment, the ultrasonic radiation force generating system includes a radiation force generating mechanism, a signal generator, and a power amplifier. The electrical signal generated by the signal generator is amplified by the power amplifier, and the excitation radiation generating mechanism generates an ultrasonic wave, and then generates a radiation force to the particle to realize the transportation and manipulation of the cell.

The flow chamber of the present application may include a substrate, a PDMS sidewall, and a glass cap, the PDMS sidewalls being bonded to the substrate while the PDMS sidewalls are also bonded to the glass cap. In one embodiment, the substrate can be made of quartz glass, plexiglass or silicon.

In one embodiment, the radiation force generating mechanism can include an ultrasonic transducer and an artificial structure. The ultrasonic transducer is placed outside the flow chamber, and the artificial structure is placed in the flow chamber, and the electrical signal amplified by the power amplifier excites the ultrasonic transducer to generate ultrasonic waves and thereby generate radiation force to the particles. The artificial structure may specifically be an artificial periodic structure or an artificial aperiodic structure. As shown in FIG. 2, the artificial periodic structure includes a substrate 11 and a plurality of ribs 12 disposed on a lower surface of the substrate 11, and the ridges 12 are disposed in parallel and at equal intervals. 2 is a schematic diagram of an artificial periodic structure employed in an acoustic radiation force generating system. t is the plate thickness, p is the period of the structure, w is the width of the grid, and h is the height of the grid. The material was stainless steel with parameters t=20-100 μm, h=10-50 μm, w=20-100 μm, p=50-300 μm. Figure 3 is a transmission spectrum of the artificial periodic structure shown in Figure 2, with a resonant frequency of 5.94 MHz.

The ultrasonic radiation force generating system of the present application, wherein the ultrasonic transducer is disposed outside the flow chamber, and the ultrasonic transducer does not coincide with the geometric center of the artificial periodic structure. In one embodiment, the ultrasonic transducer can be affixed to the exterior of the flow chamber, specifically to the lower surface of the substrate. The ultrasonic transducer can be a biased Gaussian beam source. The artificial structure modulating the ultrasonic transducer emits a sound field to produce a sound field with manipulation functions such as transport and alignment, thereby achieving cell focusing and transport.

The numerical simulation studies the acoustic radiation force of the cells in the sound field obtained by artificially modulating the Gaussian sound beam, and reveals the mechanism of the artificial structure to transport the micro-nano particles. Figure 4 shows the distribution of the sound field in the x-direction of the artificial periodic structure. It can be seen that the sound pressure distribution obeys the Gaussian distribution, where the dotted line is the theoretical calculation value and the solid line part is the experimental measurement value. As shown in Fig. 5, the cells are subjected to acoustic radiation forces in the three directions of x, y, and z in the artificial structure sound field, wherein the x-direction acoustic radiation force Fx causes the orientation movement of the micro-nano particles toward the strongest direction of the sound field to achieve transport; The acoustic radiation force Fy in the y direction causes the arrangement of the micro/nano particles to achieve focusing, and the confinement effect on the particles limits the lateral motion interval of the micro/nano particles, forming a virtual microcavity; the acoustic radiation force Fz in the z direction is responsible for Suspension and capture of micro-nano particles. The combined action of the acoustic radiation forces in these three directions ultimately leads to the transport and focusing of the cells.

Fig. 6 is a view showing the sound pressure field distribution and the directions of the radiation force components Fy and Fz at the time of resonance of the artificial periodic structure in the yz plane (resonance frequency is 5.94 MHz). Fig. 7 is a view showing the distribution of the radiation force components Fy and Fz in the y direction when the artificial periodic structure resonates in the yz plane (resonance frequency is 5.94 MHz). It can be seen that in the equilibrium position shown by the circle, the radiation force component Fz is negative, that is, vertically downward, so that the cells are stably captured on the surface of the structure.

Fig. 8 is a diagram showing the sound pressure field (driving frequency of 5.92 MHz) and the directions of the radiating force components Fy and Fz at the time of non-resonance calculation by numerical simulation. Fig. 9 is a spatial distribution of the sound pressure field (driving frequency of 5.92 MHz) and the radiation force components Fy and Fz along the y direction obtained by numerical simulation. Figure 8 is a schematic diagram of the sound field distribution and force in the yz plane. It can be seen that the sound field morphology at the time of non-resonance is very different from the sound pressure field distribution at the time of resonance in Figure 6. The position shown by the circle is the equilibrium position of the particles in the sound field. In this position, in the z direction, the vertical upward radiating force component Fz just counteracts the action of gravity to suspend the particles; in the y direction, the acoustic radiation force component Fy=0 in the position y, and the deviation from the position Fy is not zero, the direction It is pointed to the position, so the position is the equilibrium position of the particles in the y direction, and is arranged one by one in the transport direction, thereby achieving focusing.

Fig. 10 is a spatial distribution of the non-resonant (driving frequency 5.92 MHz) radiation force components Fx and Fz along the transport direction x obtained by numerical simulation. The position of x=0 is the center position of the sound source, where the sound pressure is the largest. It can be seen that the radiation force component Fz is always a positive value, meaning that the direction of the force is opposite to the direction of gravity, so that the particles can be suspended. The radiation force component Fx is zero at the center of the sound source (x = 0) and always positive at a position away from the center of the sound source. This means that the direction of the radiating force component Fx is directed towards the center of the sound source, so that the radiating force component Fx drives the particles to be oriented and transported towards the sound source.

Since the present application utilizes acoustic radiation force to manipulate cell particles for transport and focusing, there is no need for a complicated pump system to drive the control fluid, nor to introduce a sheath fluid; since the present application utilizes a virtual channel composed of acoustic radiation forces to align cells, it does not need to be present. There are microchannels used in the technology, thus avoiding the problem of clogging of the channel; multi-row parallel processing is realized by multi-line focusing due to the arrangement of multiple rows of cells due to acoustic radiation force; due to the cell manipulation module in the present application The components such as the flow chamber are low in cost and simple in process, and can be replaced with new devices each time a new sample is measured, thereby avoiding the problem of contamination of the new sample by the residue in the flow channel in the prior art. In summary, the present application provides a flow-free cell detection solution without microfluidic channels, no microfluidic pumps, no sheath fluid, disposable, parallel processing, and low cost.

Embodiment 2:

Embodiment 2 is a specific application example of the acoustically driven flow cytometry apparatus of the present application. The artificial periodic structure shown in Fig. 2 was prepared by using C304 stainless steel based on a standard chemical etching process, and its parameters were t = 30 μm, h = 20 μm, w = 50 μm, and p = 200 μm. The flow cell consists of a quartz glass substrate, a PDMS (polydimethylsiloxane) wall and a glass top cover. The PDMS wall can be bonded to the substrate and the top cover. The ultrasonic transducer is a PZT4 piezoelectric ceramic piece with a center frequency of 6 MHz and is bonded to the glass substrate by an epoxy resin. The geometric center of the ultrasonic transducer does not coincide with the geometric center of the artificial periodic structure, that is, the ultrasonic transducer needs to be biased, and the purpose is to generate a biased sound source, so that the cell particles deviating from the center of the sound source are subjected to the image as shown in FIG. The illustrated radiation force Fx acts to direct the transport to the sound source. The control software control signal generator (AFG3102, Tektronix, Beaverton, OR, USA) generates Chirp signals with a frequency of 5.90-5.94 MHz and is amplified by a power amplifier (150A100B, Amplifier Research, Souderton, PA, USA) to excite the piezoelectric ceramics. The sheet PZT4 produces ultrasonic waves. The ultrasonically excited artificial periodic structure produces a localized field as shown in Figure 8 on its surface and produces the acoustic radiation force shown in Figures 9-10 for the cellular particles. When the cells are transported to the detection area, the fluorescent excitation source is a 100W high-pressure mercury lamp that excites the stained cells to fluoresce, and a highly sensitive fluorescent camera (QIMAGING optiMOS) records the fluorescent images and transmits the data to a computer. The image analysis processing software extracts the fluorescence intensity distribution of the image and further calculates the size and number of cells.

Figure 11 is an image acquired using an acoustically driven flow cytometry system. The cells used in the experiment were MCF-7 tumor cells having a diameter of 15 μm. The cells were stained with calcein fluorescent dye and injected into the flow cell. The radiation generated by the ultrasonic radiation force generating system aligns these cells and transports these cells to the detection area. When these cells reach the detection area, the fluorescent excitation source excites the stained cells to emit green fluorescence, and the fluorescence image is recorded by a highly sensitive fluorescent camera and transmitted to the computer via a high-speed acquisition card. The image analysis processing software of the computer automatically extracts the fluorescence intensity curve, and calculates the cell size and the number of cells according to the peak size and the number of peaks, respectively. Figure 11 extracts the fluorescence intensity curves of a single column of cells in the dashed box.

Embodiment 3:

The difference between the third embodiment and the first embodiment is that the structure of the radiation force generating mechanism is different. As shown in FIG. 12, the radiation force generating mechanism may include a plurality of transducers that are placed outside the flow chamber and used to synthesize the sound field.

In one embodiment, the plurality of transducers includes at least one ultrasonic transducer and interdigitated transducers arranged in pairs and arranged in parallel, the interdigital transducers for synthesizing standing wave field alignment cells for focusing, ultrasonic transposition The energy device is used to generate a biased Gaussian beam to transport the cells. The interdigital transducers may have a pair or a plurality of teams, and FIG. 12 includes a pair of interdigital transducers, namely a first interdigital transducer 13 and a second interdigital transducer 14, wherein the ultrasonic transducer is transposed The device 15 uses a piezoelectric transducer PZT, 40 is a cell. The interdigital transducer 1 and the interdigital transducer 2 are used to synthesize a standing wave field array of cells for focusing, and the piezoelectric transducer PZT is used to generate a biased Gaussian beam for transporting cells.

The ultrasonic radiation force generation system may include a plurality of ultrasonic transducers, a signal generator, and a power amplifier. A portion of the ultrasonic transducer is used to manipulate the cell alignment focus; another portion of the transducer acts as a biased Gaussian beam source to drive particle transport. The sound field synthesized by a plurality of ultrasonic transducers to generate sound waves produces a sound field with manipulation functions such as transport and alignment, thereby achieving cell focusing and transport.

The above content is a further detailed description of the present application in conjunction with the specific embodiments, and the specific implementation of the present application is not limited to the description. For the ordinary person skilled in the art to which the present invention pertains, a number of simple deductions or substitutions may be made without departing from the spirit of the present application.

Claims

An acoustically driven flow cytometry apparatus comprising a cell manipulation module for manipulating cell particles in a sample solution, and an image processing module for smearing the stained cell particles Fluorescence imaging is performed, the image processing module is for processing and analyzing a fluorescent image, counting cell particles and estimating cell particle size, wherein the cell manipulation module comprises a flow chamber and an ultrasonic radiation force generating system, the flow chamber For containing a sample solution containing cell particles; the ultrasonic radiation force generating system is used for generating an acoustic radiation force on the cell particles, and the manipulation cell particles are arranged in parallel lines to achieve multi-line focusing, suspending the cell particles, and driving the cells at the same time. The particles are transported directionalally to the detection area to achieve multi-channel parallel detection.
The acoustically driven flow cytometry apparatus according to claim 1, wherein said ultrasonic radiation force generating system comprises a radiation force generating mechanism, a signal generator and a power amplifier, and said signal generator generates an electrical signal After the power amplifier is amplified, the excitation radiation force generating mechanism generates ultrasonic waves and thereby generates a radiation force to the particles to effect transport and manipulation of the cells.
The acoustically driven flow cytometric device of claim 2 wherein said flow chamber comprises a substrate, a PDMS sidewall and a glass cap, said PDMS sidewalls being associated with said substrate and said glass dome, respectively The lid is bonded, and the substrate is made of quartz glass, plexiglass or silicon.
The acoustically driven flow cytometry apparatus according to claim 3, wherein said radiation force generating mechanism comprises an ultrasonic transducer and an artificial structure placed in the flow chamber, the electrical signal amplified by said power amplifier Exciting the ultrasonic transducer to generate ultrasonic waves and thereby generate a radiation force to the particles.
The acoustically driven flow cytometric device of claim 4 wherein said artificial structure comprises an artificial periodic structure or an artificial aperiodic structure.
The acoustically driven flow cytometry apparatus according to claim 5, wherein said artificial periodic structure comprises a substrate and a plurality of ridges disposed on a lower surface of said substrate, said ridges being arranged in parallel and at equal intervals .
The acoustically driven flow cytometric device of claim 4 wherein said artificial structure is constructed of a stainless steel material.
The acoustically driven flow cytometric device of claim 6 wherein said ultrasonic transducer is disposed outside said flow chamber and said ultrasonic transducer is geometrically centered with said artificial periodic structure Do not coincide.
The acoustically driven flow cytometric device of claim 3 wherein said radiation force generating mechanism comprises a plurality of transducers disposed outside of the flow chamber for synthesizing the sound field.
The acoustically driven flow cytometric device of claim 9 wherein said plurality of transducers comprises at least one ultrasonic transducer and interdigitated transducers arranged in pairs and arranged in parallel, said An interdigital transducer is used to synthesize a standing wave field array of cells for focusing, and the ultrasonic transducer is used to generate a biased Gaussian beam to transport cells.